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ΓòÉΓòÉΓòÉ 1. Title page ΓòÉΓòÉΓòÉ

                                GNU Emacs Manual

                        Eighth Edition, Emacs version 19

                                 for Unix Users

                                    June 1993

                                Richard Stallman

Copyright (C) 1985, 1986, 1987, 1993 Free Software Foundation, Inc.

Eighth Edition
For Emacs Version 19,
Printed June, 1993.

ISBN 1-882114-02-7

Published by the Free Software Foundation
675 Massachusetts Avenue
Cambridge, MA 02139 USA

Permission is granted to make and distribute verbatim copies of this manual
provided the copyright notice and this permission notice are preserved on all
copies.

Permission is granted to copy and distribute modified versions of this manual
under the conditions for verbatim copying, provided also that the sections
entitled ``The GNU Manifesto'', ``Distribution'' and ``GNU Emacs General Public
License'' are included exactly as in the original, and provided that the entire
resulting derived work is distributed under the terms of a permission notice
identical to this one.

Permission is granted to copy and distribute translations of this manual into
another language, under the above conditions for modified versions, except that
the sections entitled ``The GNU Manifesto'', ``Distribution'' and ``GNU Emacs
General Public License'' may be included in a translation approved by the Free
Software Foundation instead of in the original English.


ΓòÉΓòÉΓòÉ 2. Top ΓòÉΓòÉΓòÉ

The Emacs Editor ****************

Emacs is the extensible, customizable, self-documenting real-time display
editor.  This Info file describes how to edit with Emacs and some of how to
customize it, but not how to extend it.  It corresponds to GNU Emacs version
19.17.


ΓòÉΓòÉΓòÉ 3. Distribution ΓòÉΓòÉΓòÉ

GNU Emacs is free; this means that everyone is free to use it and free to
redistribute it on certain conditions.  GNU Emacs is not in the public domain;
it is copyrighted and there are restrictions on its distribution, but these
restrictions are designed to permit everything that a good cooperating citizen
would want to do.  What is not allowed is to try to prevent others from further
sharing any version of GNU Emacs that they might get from you.  The precise
conditions are found in the GNU Emacs General Public License that comes with
Emacs and also appears following this section.

The easiest way to get a copy of GNU Emacs is from someone else who has it.
You need not ask for permission to do so, or tell any one else; just copy it.
If you have access to the Internet, you can get the latest distribution version
of GNU Emacs from host `prep.ai.mit.edu' using anonymous login.  See the file
`/pub/gnu/GETTING.GNU.SOFTWARE' on that host to find out about your options for
copying and which files to use.

You may also receive GNU Emacs when you buy a computer.  Computer manufacturers
are free to distribute copies on the same terms that apply to everyone else.
These terms require them to give you the full sources, including whatever
changes they may have made, and to permit you to redistribute the GNU Emacs
received from them under the usual terms of the General Public License.  In
other words, the program must be free for you when you get it, not just free
for the manufacturer.

You can also order copies of GNU Emacs from the Free Software Foundation, on
various magnetic media or on CD-ROM.  This is a convenient and reliable way to
get a copy; it is also a good way to help fund our work.  (The Foundation has
always received most of its funds in this way.)  An order form is included at
the end of manuals printed by the Foundation.  It is also included in the file
`etc/ORDERS' in the Emacs distribution.  For further information, write to

Free Software Foundation
675 Mass Ave
Cambridge, MA 02139
USA

The income from distribution fees goes to support the foundation's purpose: the
development of new free software, and improvements to our existing programs
including GNU Emacs.

If you find GNU Emacs useful, please *send a donation* to the Free Software
Foundation to support our work.  Donations to the Free Software Foundation are
tax deductible.  If you use GNU Emacs at your workplace, suggest that the
company make a donation.  If the management of your office opposes the idea of
donations, you might instead suggest ordering a CD-ROM from the Foundation
occasionally.


ΓòÉΓòÉΓòÉ 4. GNU GENERAL PUBLIC LICENSE ΓòÉΓòÉΓòÉ

                              Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.


ΓòÉΓòÉΓòÉ 4.1. Preamble ΓòÉΓòÉΓòÉ

 The licenses for most software are designed to take away your freedom to share
and change it.  By contrast, the GNU General Public License is intended to
guarantee your freedom to share and change free software---to make sure the
software is free for all its users.  This General Public License applies to
most of the Free Software Foundation's software and to any other program whose
authors commit to using it.  (Some other Free Software Foundation software is
covered by the GNU Library General Public License instead.)  You can apply it
to your programs, too.

 When we speak of free software, we are referring to freedom, not price.  Our
General Public Licenses are designed to make sure that you have the freedom to
distribute copies of free software (and charge for this service if you wish),
that you receive source code or can get it if you want it, that you can change
the software or use pieces of it in new free programs; and that you know you
can do these things.

 To protect your rights, we need to make restrictions that forbid anyone to
deny you these rights or to ask you to surrender the rights. These restrictions
translate to certain responsibilities for you if you distribute copies of the
software, or if you modify it.

 For example, if you distribute copies of such a program, whether gratis or for
a fee, you must give the recipients all the rights that you have.  You must
make sure that they, too, receive or can get the source code.  And you must
show them these terms so they know their rights.

 We protect your rights with two steps: (1) copyright the software, and (2)
offer you this license which gives you legal permission to copy, distribute
and/or modify the software.

 Also, for each author's protection and ours, we want to make certain that
everyone understands that there is no warranty for this free software.  If the
software is modified by someone else and passed on, we want its recipients to
know that what they have is not the original, so that any problems introduced
by others will not reflect on the original authors' reputations.

 Finally, any free program is threatened constantly by software patents.  We
wish to avoid the danger that redistributors of a free program will
individually obtain patent licenses, in effect making the program proprietary.
To prevent this, we have made it clear that any patent must be licensed for
everyone's free use or not licensed at all.

 The precise terms and conditions for copying, distribution and modification
follow.

         TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

 1. This License applies to any program or other work which contains a notice
    placed by the copyright holder saying it may be distributed under the terms
    of this General Public License.  The ``Program'', below, refers to any such
    program or work, and a ``work based on the Program'' means either the
    Program or any derivative work under copyright law: that is to say, a work
    containing the Program or a portion of it, either verbatim or with
    modifications and/or translated into another language.  (Hereinafter,
    translation is included without limitation in the term ``modification''.)
    Each licensee is addressed as ``you''.

    Activities other than copying, distribution and modification are not
    covered by this License; they are outside its scope.  The act of running
    the Program is not restricted, and the output from the Program is covered
    only if its contents constitute a work based on the Program (independent of
    having been made by running the Program). Whether that is true depends on
    what the Program does.

 2. You may copy and distribute verbatim copies of the Program's source code as
    you receive it, in any medium, provided that you conspicuously and
    appropriately publish on each copy an appropriate copyright notice and
    disclaimer of warranty; keep intact all the notices that refer to this
    License and to the absence of any warranty; and give any other recipients
    of the Program a copy of this License along with the Program.

    You may charge a fee for the physical act of transferring a copy, and you
    may at your option offer warranty protection in exchange for a fee.

 3. You may modify your copy or copies of the Program or any portion of it,
    thus forming a work based on the Program, and copy and distribute such
    modifications or work under the terms of Section 1 above, provided that you
    also meet all of these conditions:

    a. You must cause the modified files to carry prominent notices stating
       that you changed the files and the date of any change.

    b. You must cause any work that you distribute or publish, that in whole or
       in part contains or is derived from the Program or any part thereof, to
       be licensed as a whole at no charge to all third parties under the terms
       of this License.

    c. If the modified program normally reads commands interactively when run,
       you must cause it, when started running for such interactive use in the
       most ordinary way, to print or display an announcement including an
       appropriate copyright notice and a notice that there is no warranty (or
       else, saying that you provide a warranty) and that users may
       redistribute the program under these conditions, and telling the user
       how to view a copy of this License.  (Exception: if the Program itself
       is interactive but does not normally print such an announcement, your
       work based on the Program is not required to print an announcement.)

    These requirements apply to the modified work as a whole.  If identifiable
    sections of that work are not derived from the Program, and can be
    reasonably considered independent and separate works in themselves, then
    this License, and its terms, do not apply to those sections when you
    distribute them as separate works.  But when you distribute the same
    sections as part of a whole which is a work based on the Program, the
    distribution of the whole must be on the terms of this License, whose
    permissions for other licensees extend to the entire whole, and thus to
    each and every part regardless of who wrote it.

    Thus, it is not the intent of this section to claim rights or contest your
    rights to work written entirely by you; rather, the intent is to exercise
    the right to control the distribution of derivative or collective works
    based on the Program.

    In addition, mere aggregation of another work not based on the Program with
    the Program (or with a work based on the Program) on a volume of a storage
    or distribution medium does not bring the other work under the scope of
    this License.

 4. You may copy and distribute the Program (or a work based on it, under
    Section 2) in object code or executable form under the terms of Sections 1
    and 2 above provided that you also do one of the following:

    a. Accompany it with the complete corresponding machine-readable source
       code, which must be distributed under the terms of Sections 1 and 2
       above on a medium customarily used for software interchange; or,

    b. Accompany it with a written offer, valid for at least three years, to
       give any third party, for a charge no more than your cost of physically
       performing source distribution, a complete machine-readable copy of the
       corresponding source code, to be distributed under the terms of Sections
       1 and 2 above on a medium customarily used for software interchange; or,

    c. Accompany it with the information you received as to the offer to
       distribute corresponding source code.  (This alternative is allowed only
       for noncommercial distribution and only if you received the program in
       object code or executable form with such an offer, in accord with
       Subsection b above.)

    The source code for a work means the preferred form of the work for making
    modifications to it.  For an executable work, complete source code means
    all the source code for all modules it contains, plus any associated
    interface definition files, plus the scripts used to control compilation
    and installation of the executable.  However, as a special exception, the
    source code distributed need not include anything that is normally
    distributed (in either source or binary form) with the major components
    (compiler, kernel, and so on) of the operating system on which the
    executable runs, unless that component itself accompanies the executable.

    If distribution of executable or object code is made by offering access to
    copy from a designated place, then offering equivalent access to copy the
    source code from the same place counts as distribution of the source code,
    even though third parties are not compelled to copy the source along with
    the object code.

 5. You may not copy, modify, sublicense, or distribute the Program except as
    expressly provided under this License.  Any attempt otherwise to copy,
    modify, sublicense or distribute the Program is void, and will
    automatically terminate your rights under this License. However, parties
    who have received copies, or rights, from you under this License will not
    have their licenses terminated so long as such parties remain in full
    compliance.

 6. You are not required to accept this License, since you have not signed it.
    However, nothing else grants you permission to modify or distribute the
    Program or its derivative works.  These actions are prohibited by law if
    you do not accept this License.  Therefore, by modifying or distributing
    the Program (or any work based on the Program), you indicate your
    acceptance of this License to do so, and all its terms and conditions for
    copying, distributing or modifying the Program or works based on it.

 7. Each time you redistribute the Program (or any work based on the Program),
    the recipient automatically receives a license from the original licensor
    to copy, distribute or modify the Program subject to these terms and
    conditions.  You may not impose any further restrictions on the recipients'
    exercise of the rights granted herein. You are not responsible for
    enforcing compliance by third parties to this License.

 8. If, as a consequence of a court judgment or allegation of patent
    infringement or for any other reason (not limited to patent issues),
    conditions are imposed on you (whether by court order, agreement or
    otherwise) that contradict the conditions of this License, they do not
    excuse you from the conditions of this License.  If you cannot distribute
    so as to satisfy simultaneously your obligations under this License and any
    other pertinent obligations, then as a consequence you may not distribute
    the Program at all.  For example, if a patent license would not permit
    royalty-free redistribution of the Program by all those who receive copies
    directly or indirectly through you, then the only way you could satisfy
    both it and this License would be to refrain entirely from distribution of
    the Program.

    If any portion of this section is held invalid or unenforceable under any
    particular circumstance, the balance of the section is intended to apply
    and the section as a whole is intended to apply in other circumstances.

    It is not the purpose of this section to induce you to infringe any patents
    or other property right claims or to contest validity of any such claims;
    this section has the sole purpose of protecting the integrity of the free
    software distribution system, which is implemented by public license
    practices.  Many people have made generous contributions to the wide range
    of software distributed through that system in reliance on consistent
    application of that system; it is up to the author/donor to decide if he or
    she is willing to distribute software through any other system and a
    licensee cannot impose that choice.

    This section is intended to make thoroughly clear what is believed to be a
    consequence of the rest of this License.

 9. If the distribution and/or use of the Program is restricted in certain
    countries either by patents or by copyrighted interfaces, the original
    copyright holder who places the Program under this License may add an
    explicit geographical distribution limitation excluding those countries, so
    that distribution is permitted only in or among countries not thus
    excluded.  In such case, this License incorporates the limitation as if
    written in the body of this License.

10. The Free Software Foundation may publish revised and/or new versions of the
    General Public License from time to time.  Such new versions will be
    similar in spirit to the present version, but may differ in detail to
    address new problems or concerns.

    Each version is given a distinguishing version number.  If the Program
    specifies a version number of this License which applies to it and ``any
    later version'', you have the option of following the terms and conditions
    either of that version or of any later version published by the Free
    Software Foundation.  If the Program does not specify a version number of
    this License, you may choose any version ever published by the Free
    Software Foundation.

11. If you wish to incorporate parts of the Program into other free programs
    whose distribution conditions are different, write to the author to ask for
    permission.  For software which is copyrighted by the Free Software
    Foundation, write to the Free Software Foundation; we sometimes make
    exceptions for this.  Our decision will be guided by the two goals of
    preserving the free status of all derivatives of our free software and of
    promoting the sharing and reuse of software generally.

                                     NO WARRANTY

12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
    THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
    OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
    PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER
    EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK
    AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
    PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
    REPAIR OR CORRECTION.

13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL
    ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE
    THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
    GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
    USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
    DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
    PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
    EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
    SUCH DAMAGES.

                           END OF TERMS AND CONDITIONS


ΓòÉΓòÉΓòÉ 4.2. How to Apply These Terms to Your New Programs ΓòÉΓòÉΓòÉ

 If you develop a new program, and you want it to be of the greatest possible
use to the public, the best way to achieve this is to make it free software
which everyone can redistribute and change under these terms.

 To do so, attach the following notices to the program.  It is safest to attach
them to the start of each source file to most effectively convey the exclusion
of warranty; and each file should have at least the ``copyright'' line and a
pointer to where the full notice is found.

one line to give the program's name and an idea of what it does.
Copyright (C) 19yy  name of author

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it
starts in an interactive mode:

Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
type `show w'.  This is free software, and you are welcome
to redistribute it under certain conditions; type `show c'
for details.

The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License.  Of course, the commands you use may be
called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items---whatever suits your program.

You should also get your employer (if you work as a programmer) or your school,
if any, to sign a ``copyright disclaimer'' for the program, if necessary.  Here
is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright
interest in the program `Gnomovision'
(which makes passes at compilers) written
by James Hacker.

signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice

This General Public License does not permit incorporating your program into
proprietary programs.  If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library.  If this is what you want to do, use the GNU Library General Public
License instead of this License.


ΓòÉΓòÉΓòÉ 5. Introduction ΓòÉΓòÉΓòÉ

 You are reading about GNU Emacs, the GNU incarnation of the advanced,
self-documenting, customizable, extensible real-time display editor Emacs. (The
`G' in `GNU' is not silent.)

 We say that Emacs is a display editor because normally the text being edited
is visible on the screen and is updated automatically as you type your
commands.  See Screen.

 We call it a real-time editor because the display is updated very frequently,
usually after each character or pair of characters you type.  This minimizes
the amount of information you must keep in your head as you edit.  See Basic
Editing.

 We call Emacs advanced because it provides facilities that go beyond simple
insertion and deletion: filling of text; automatic indentation of programs;
viewing two or more files at once; and dealing in terms of characters, words,
lines, sentences, paragraphs, and pages, as well as expressions and comments in
several different programming languages.

 Self-documenting means that at any time you can type a special character,
Control-h, to find out what your options are.  You can also use it to find out
what any command does, or to find all the commands that pertain to a topic.
See Help.

 Customizable means that you can change the definitions of Emacs commands in
little ways.  For example, if you use a programming language in which comments
start with `<**' and end with `**>', you can tell the Emacs comment
manipulation commands to use those strings (see Comments).  Another sort of
customization is rearrangement of the command set.  For example, if you prefer
the four basic cursor motion commands (up, down, left and right) on keys in a
diamond pattern on the keyboard, you can have it.  See Customization.

 Extensible means that you can go beyond simple customization and write
entirely new commands, programs in the Lisp language to be run by Emacs's own
Lisp interpreter.  Emacs is an ``on-line extensible'' system, which means that
it is divided into many functions that call each other, any of which can be
redefined in the middle of an editing session.  Any part of Emacs can be
replaced without making a separate copy of all of Emacs.  Most of the editing
commands of Emacs are written in Lisp already; the few exceptions could have
been written in Lisp but are written in C for efficiency.  Although only a
programmer can write an extension, anybody can use it afterward.

  When run under the X Window System, Emacs provides its own menus and
convenient bindings to mouse buttons.  But Emacs can provide many of the
benefits of a window system on a text-only terminal.  For instance, you can
look at or edit several files at once, move text between them, and edit files
at the same time as you run shell commands.


ΓòÉΓòÉΓòÉ 6. The Organization of the Screen ΓòÉΓòÉΓòÉ

 On a text-only terminal, the Emacs display occupies the whole screen. On the X
Window System, Emacs creates its own X windows to use.  We use the term frame
to mean an entire text-only screen or an entire X window used by Emacs.  Emacs
uses both kinds of frames in the same way to display your editing.  Emacs
normally starts out with just one frame, but under X you can create additional
frames if you wish.  See Frames.

 When you start Emacs, the entire frame except for the last line is devoted to
the text you are editing.  This area is called window. The last line is a
special echo area or minibuffer window where prompts appear and where you can
enter responses.  You can subdivide the large text window horizontally or
vertically into multiple text windows, each of which can be used for a
different file (see Windows).  In this manual, the word ``window'' always
refers to the subdivisions of a frame within Emacs.

 The window that the cursor is in is the selected window, in which editing
takes place.  Most Emacs commands implicitly apply to the text in the selected
window.  The other windows display text for reference only, unless/until you
select them.

 Each window's last line is a mode line which describes what is going on in
that window.  It is in inverse video if the terminal supports that, and
contains text that starts like `-----Emacs: something'.  Its purpose is to
indicate what buffer is being displayed above it in the window; what major and
minor modes are in use; and whether the buffer contains unsaved changes.


ΓòÉΓòÉΓòÉ 6.1. Point ΓòÉΓòÉΓòÉ

 Within Emacs, the terminal's cursor shows the location at which editing
commands will take effect.  This location is called point.  Other commands move
point through the text, so that you can edit at different places in it.

 While the cursor appears to point at a character, you should think of point as
between two characters; it points before the character that appears under the
cursor.  For example, if your text looks like `frob' with the cursor over the
`b', then point is between the `o' and the `b'.  If you insert the character
`!' at that position, the result is `fro!b', with point between the `!' and the
`b'.  Thus, the cursor remains over the `b', as before.

 Sometimes people speak of ``the cursor'' when they mean ``point'', or speak of
commands that move point as ``cursor motion'' commands.

 Terminals have only one cursor, and when output is in progress it must appear
where the typing is being done.  This does not mean that point is moving.  It
is only that Emacs has no way to show you the location of point except when the
terminal is idle.

 If you are editing several files in Emacs, each in its own buffer, each buffer
has its own point location.  A buffer that is not currently displayed remembers
where point is in case you display it again later.

 When there are multiple windows, each window has its own point location.  The
cursor shows the location of point in the selected window.  This also is how
you can tell which window is selected.  If the same buffer appears in more than
one window, each window has its own position for point in that buffer.

 The term `point' comes from the character `.', which was the command in TECO
(the language in which the original Emacs was written) for accessing the value
now called `point'.


ΓòÉΓòÉΓòÉ 6.2. The Echo Area ΓòÉΓòÉΓòÉ

 The line at the bottom of the screen (below the mode line) is the echo area.
It is used to display small amounts of text for several purposes.

 Echoing means printing out the characters that you type. Outside Emacs, the
operating system normally echoes all your input. Emacs handles echoing
differently.

 Single-character commands do not echo in Emacs, and multi-character commands
echo only if you pause while typing them.  As soon as you pause for more than a
second in the middle of a command, Emacs echoes all the characters of the
command so far.  This is to prompt you for the rest of the command.  Once
echoing has started, the rest of the command echoes immediately as you type it.
This behavior is designed to give confident users fast response, while giving
hesitant users maximum feedback.  You can change this behavior by setting a
variable (see Display Vars).

 If a command cannot be executed, it may print an error message in the echo
area.  Error messages are accompanied by a beep or by flashing the screen.
Also, any input you have typed ahead is thrown away when an error happens.

 Some commands print informative messages in the echo area.  These messages
look much like error messages, but they are not announced with a beep and do
not throw away input.  Sometimes the message tells you what the command has
done, when this is not obvious from looking at the text being edited.
Sometimes the sole purpose of a command is to print a message giving you
specific information---for example, C-x = prints a message describing the
character position of point in the text and its current column in the window.
Commands that take a long time often display messages ending in `...' while
they are working, and add `done' at the end when they are finished.

 The echo area is also used to display the minibuffer, a window that is used
for reading arguments to commands, such as the name of a file to be edited.
When the minibuffer is in use, the echo area begins with a prompt string that
usually ends with a colon; also, the cursor appears in that line because it is
the selected window.  You can always get out of the minibuffer by typing C-g.
See Minibuffer.


ΓòÉΓòÉΓòÉ 6.3. The Mode Line ΓòÉΓòÉΓòÉ

 Each text window's last line is a mode line which describes what is going on
in that window.  When there is only one text window, the mode line appears
right above the echo area.  The mode line is in inverse video if the terminal
supports that, starts and ends with dashes, and contains text like `Emacs:
something'.

 If a mode line has something else in place of `Emacs: something', then the
window above it is in a special subsystem such as Dired.  The mode line then
indicates the status of the subsystem.

 Normally, the mode line looks like this:

--ch-Emacs: buf      (major minor)----pos------

This gives information about the buffer being displayed in the window: the
buffer's name, what major and minor modes are in use, whether the buffer's text
has been changed, and how far down the buffer you are currently looking.

 ch contains two stars `**' if the text in the buffer has been edited (the
buffer is ``modified''), or `--' if the buffer has not been edited.  Exception:
for a read-only buffer, it is `%%'.

 buf is the name of the window's buffer.  In most cases this is the same as the
name of a file you are editing.  See Buffers.

 The buffer displayed in the selected window (the window that the cursor is in)
is also Emacs's selected buffer, the one that editing takes place in.  When we
speak of what some command does to ``the buffer'', we are talking about the
currently selected buffer.

 pos tells you whether there is additional text above the top of the window, or
below the bottom.  If your buffer is small and it is all visible in the window,
pos is `All'.  Otherwise, it is `Top' if you are looking at the beginning of
the buffer, `Bot' if you are looking at the end of the buffer, or `nn%', where
nn is the percentage of the buffer above the top of the window.

 major is the name of the major mode in effect in the buffer.  At any time,
each buffer is in one and only one of the possible major modes. The major modes
available include Fundamental mode (the least specialized), Text mode, Lisp
mode, and C mode.  See Major Modes, for details of how the modes differ and how
to select one.

 minor is a list of some of the minor modes that are turned on at the moment in
the window's chosen buffer.  `Fill' means that Auto Fill mode is on.  `Abbrev'
means that Word Abbrev mode is on. `Ovwrt' means that Overwrite mode is on.
See Minor Modes, for more information.  `Narrow' means that the buffer being
displayed has editing restricted to only a portion of its text.  This is not
really a minor mode, but is like one.  See Narrowing.  `Def' means that a
keyboard macro is being defined.  See Keyboard Macros.

 Some buffers display additional information after the minor modes.  For
example, Rmail buffers display the current message number and the total number
of messages.  Compilation buffers and Shell mode display the status of the
subprocess.

 In addition, if Emacs is currently inside a recursive editing level, square
brackets (`[...]') appear around the parentheses that surround the modes.  If
Emacs is in one recursive editing level within another, double square brackets
appear, and so on.  Since recursive editing levels affect Emacs globally and
not any one buffer, the square brackets appear in every window's mode line or
not in any of them. See Recursive Edit.

 See Optional Display, for features that add other handy information to the
mode line, such as the current line number of point, the current time, and
whether mail has arrived for you.


ΓòÉΓòÉΓòÉ 6.4. Keyboard Input ΓòÉΓòÉΓòÉ

 GNU Emacs uses an extension of the ASCII character set for keyboard input.
ASCII consists of 128 character codes.  Some of these codes are assigned
graphic symbols such as `a' and `='; the rest are control characters, such as
Control-a (usually written C-a for short).  C-a gets its name from the fact
that you type it by holding down the CTRL key and then pressing a.

 Some control characters have special names, and special keys you can type them
with: for example, RET, TAB, LFD, DEL and ESC.  The space character is usually
referred to below as SPC, even though strictly speaking it is a graphic
character whose graphic happens to be blank.

 On ASCII terminals, the shift key is meaningless with control characters: C-a
and C-A are the same character, and Emacs cannot distinguish them.  Under X
Windows, these are distinct characters, but the standard key bindings treat
them the same in all contexts.

 On ASCII terminals, there are only 32 possible control characters. These are
the control variants of letters and `@[]\^_'.  Under X Windows, every
non-control character has a control variant.  For example, C-+ and C-5 are
meaningful under X.

 Emacs extends the ASCII character code by adding an extra bit to each
character.  The additional bit is called Meta.  Any character can be made Meta;
examples of Meta characters include Meta-a (normally written M-a, for short),
M-A (not the same character as M-a, but those two characters normally have the
same meaning in Emacs), M-RET, and M-C-a.  For traditional reasons, M-C-a is
usually called C-M-a; logically speaking, the order in which the modifier keys
CTRL and META are mentioned does not matter.

 Some terminals have a META key, and allow you to type Meta characters by
holding this key down.  Thus, Meta-a is typed by holding down META and pressing
a.  The META key works much like the SHIFT key.  Such a key is not always
labeled META, however, as this function is often a special option for a key
with some other primary purpose.

 If there is no META key, you can still type Meta characters using
two-character sequences starting with ESC.  Thus, to enter M-a, you could type
ESC a.  To enter C-M-a, you would type ESC C-a.  ESC is allowed on terminals
with Meta keys, too, in case you have formed a habit of using it.

 X Windows provides several other modifier keys that can be applied to any
keyboard input character.  These are called SUPER, HYPER and ALT.  With them,
you can make characters that we denote with `s-', `H-' and `A-'.  Thus, s-H-C-x
is short for Super-Hyper-Control-x.  Not all X terminals actually provide keys
for these modifier flags, and the standard key bindings of Emacs do not include
such characters.  But you can assign them meanings of your own by customizing
Emacs.

 Keyboard input includes keyboard keys that are not characters at all: for
example function keys and arrow keys.  Mouse buttons are also outside the gamut
of characters.  These inputs do not have numeric character codes.  Instead,
Emacs represents them by their names (actually, Lisp objects called symbols).

 Input characters and non-character inputs are collectively called input
events.

 ASCII terminals cannot really send anything to the computer except ASCII
characters.  These terminals use a sequence of characters to represent each
function key.  But that is invisible to the Emacs user, because the keyboard
input routines recognize these special sequences and converts them to names
before any other part of Emacs gets to see them.


ΓòÉΓòÉΓòÉ 6.5. Keys ΓòÉΓòÉΓòÉ

 A key sequence (key, for short) is a sequence of input events that combine as
part of the invocation of a single command. Recall that input events include
both keyboard characters and non-character inputs (function keys, arrow keys,
mouse buttons, and so forth).

 If the sequence is enough to invoke a command, it is a complete key.  If it
isn't long enough to be complete, we call it a prefix key.  Examples of
complete keys include C-a, X, RET, NEXT (a function key), DOWN (an arrow key),
C-x C-f and C-x 4 C-f.

 Most single characters constitute complete keys in the standard Emacs command
bindings.  A few of them are prefix keys.  A prefix key can be followed by
additional input characters (or other events) to make a longer key, which may
itself be complete or a prefix.

 For example, C-x is a prefix key, so C-x and the next input character combine
to make a two-character key sequence.  Most of these key sequences are complete
keys, including C-x C-f and C-x b.  A few, such as C-x 4 and C-x r, are
themselves prefix keys that lead to three-character key sequences.  There's no
limit to the length of a key sequence, but any key sequence longer than one
character must be reached through a chain of prefix keys.

 By contrast, the two-character sequence C-f C-k is not a key, because the C-f
is a complete key in itself.  It's impossible to give C-f C-k an independent
meaning as a command.  C-f C-k is two key sequences, not one.

 All told, the prefix keys in Emacs are C-c, C-x, C-h, C-x C-a, C-x n, C-x r,
C-x v, C-x 4, C-x 5, and ESC.  But this is not cast in concrete; it is just a
matter of Emacs's standard key bindings.  In customizing Emacs, you could make
new prefix keys, or eliminate these. See Key Bindings.

 Whether a sequence is a key can be changed by customization.  For example, if
you redefine C-f as a prefix, C-f C-k automatically becomes a key (complete,
unless you define it too as a prefix). Conversely, if you remove the prefix
definition of C-x 4, then C-x 4 f (or C-x 4 anything) is no longer a key.


ΓòÉΓòÉΓòÉ 6.6. Keys and Commands ΓòÉΓòÉΓòÉ

 This manual is full of passages that tell you what particular keys do.  But
Emacs does not assign meanings to keys directly.  Instead, Emacs assigns
meanings to named commands, and then gives keys their meanings by binding them
to commands.

 Every command has a name chosen by a programmer.  The name is usually made of
a few English words separated by dashes; for example, next-line or
forward-word.  A command also has a function definition which is a Lisp
program; this is what makes the command do what it does.  In Emacs Lisp, a
command is actually a special kind of Lisp function; one which specifies how to
read arguments for it and call it interactively.  For more information on
commands and functions, see What Is a Function.  (The definition we use in this
manual is simplified slightly.)

 The bindings between keys and commands are recorded in various tables called
keymaps.  See Keymaps.

 When we say that ``C-n moves down vertically one line'' we are glossing over a
distinction that is irrelevant in ordinary use but is vital in understanding
how to customize Emacs.  It is the command next-line that is programmed to move
down vertically.  C-n has this effect because it is bound to that command.  If
you rebind C-n to the command forward-word then C-n will move forward by words
instead.  Rebinding keys is a common method of customization.

 In the rest of this manual, we usually ignore this subtlety to keep things
simple.  To give the customizer the information he needs, we state the name of
the command which really does the work in parentheses after mentioning the key
that runs it.  For example, we will say that ``The command C-n (next-line)
moves point vertically down,'' meaning that next-line is a command that moves
vertically down and C-n is a key that is standardly bound to it.

 While we are on the subject of information for customization only, it's a good
time to tell you about variables.  Often the description of a command will say,
``To change this, set the variable mumble-foo.'' A variable is a name used to
remember a value.  Most of the variables documented in this manual exist just
to facilitate customization: some command or other part of Emacs examines the
variable and behaves differently accordingly.  Until you are interested in
customizing, you can ignore the information about variables.  When you are
ready to be interested, read the basic information on variables, and then the
information on individual variables will make sense.  See Variables.


ΓòÉΓòÉΓòÉ 6.7. Character Set for Text ΓòÉΓòÉΓòÉ

 Emacs buffers use an 8-bit character set, because bytes have 8 bits. ASCII
graphic characters in Emacs buffers are displayed with their graphics.  The
newline character (which has the same character code as LFD) is displayed by
starting a new line.  The tab character is displayed by moving to the next tab
stop column (usually every 8 columns).  Other control characters are displayed
as a caret (`^') followed by the non-control version of the character; thus,
C-a is displayed as `^A'.

 Non-ASCII characters 128 and up are displayed with octal escape sequences;
thus, character code 243 (octal) is displayed as `\243'.  You can customize the
display of these character codes (or ANSI characters) by creating a display
table; this is useful for editing files that use 8-bit European character sets.
See Display Tables.


ΓòÉΓòÉΓòÉ 7. Entering and Exiting Emacs ΓòÉΓòÉΓòÉ

 The usual way to invoke Emacs is with the shell command `emacs'. Emacs clears
the screen and then displays an initial help message and copyright notice.  On
a window system, Emacs opens a window of its own. You can begin typing Emacs
commands immediately afterward.

 Some operating systems insist on discarding all type-ahead when Emacs starts
up; they give Emacs no way to prevent this.  Therefore, it is wise to wait
until Emacs clears the screen before typing your first editing command.

 If you run Emacs from a shell window under the X Window System, run it in the
background with `emacs&'.  This way, Emacs does not tie up the shell window, so
you can use it to run other shell commands while Emacs operates its own X
windows.

 When Emacs starts up, it makes a buffer named `*scratch*'. That's the buffer
you start out in.  The `*scratch*' uses Lisp Interaction mode; you can use it
to type Lisp expressions and evaluate them, or you can ignore that capability
and simply doodle.  (You can specify a different major mode for this buffer by
setting the variable initial-major-mode in your init file.  See Init File.)

 It is also possible to specify files to be visited, Lisp files to be loaded,
and functions to be called, by giving Emacs arguments in the shell command
line.  See Command Arguments.  But we don't recommend doing this.  The feature
exists mainly for compatibility with other editors.

 Many other editors are designed to be started afresh each time you want to
edit.  You edit one file and then exit the editor.  The next time you want to
edit either another file or the same one, you must run the editor again.  With
these editors, it makes sense to use a command line argument to say which file
to edit.

 But starting a new Emacs each time you want to edit a different file does not
make sense.  For one thing, this would be annoyingly slow.  For another, this
would fail to take advantage of Emacs's ability to visit more than one file in
a single editing session.

 The recommended way to use GNU Emacs is to start it only once, just after you
log in, and do all your editing in the same Emacs session. Each time you want
to edit a different file, you visit it with the existing Emacs, which
eventually comes to have many files in it ready for editing.  Usually you do
not kill the Emacs until you are about to log out.


ΓòÉΓòÉΓòÉ 7.1. Exiting Emacs ΓòÉΓòÉΓòÉ

 There are two commands for exiting Emacs because there are two kinds of
exiting: suspending Emacs and killing Emacs.

 Suspending means stopping Emacs temporarily and returning control to its
parent process (usually a shell), allowing you to resume editing later in the
same Emacs job, with the same files, same kill ring, same undo history, and so
on.  This is the usual way to exit.

 Killing Emacs means destroying the Emacs job.  You can run Emacs again later,
but you will get a fresh Emacs; there is no way to resume the same editing
session after it has been killed.

C-z
          Suspend Emacs (suspend-emacs).

C-x C-c
          Kill Emacs (save-buffers-kill-emacs).

 To suspend Emacs, type C-z (suspend-emacs).  This takes you back to the shell
from which you invoked Emacs.  You can resume Emacs with the shell command
`%emacs' in most common shells.

 On systems that do not permit programs to be suspended, C-z runs an inferior
shell that communicates directly with the terminal, and Emacs waits until you
exit the subshell.  (The way to do that is probably with C-d or `exit', but it
depends on which shell you use.)  The only way on these systems to get back to
the shell from which Emacs was run (to log out, for example) is to kill Emacs.

 When Emacs communicates directly with an X server and creates its own
dedicated X windows, C-z has a different meaning.  Suspending an applications
that uses its own X windows is not meaningful or useful. Instead, C-z runs the
command iconify-frame, which temporarily closes up the selected Emacs frame.
The way to get back to a shell window is with the window manager.

 To kill Emacs, type C-x C-c (save-buffers-kill-emacs).  A two-character key is
used for this to make it harder to type.  Unless a numeric argument is used,
this command first offers to save any modified buffers.  If you do not save
them all, it asks for reconfirmation with yes before killing Emacs, since any
changes not saved will be lost forever.  Also, if any subprocesses are still
running, C-x C-c asks for confirmation about them, since killing Emacs will
kill the subprocesses immediately.

 The operating system usually listens for certain special characters whose
meaning is to kill or suspend the program you are running. This operating
system feature is turned off while you are in Emacs. The meanings of C-z and
C-x C-c as keys in Emacs were inspired by the use of C-z and C-c on several
operating systems as the characters for stopping or killing a program, but that
is their only relationship with the operating system.  You can customize these
keys to run any commands (see Keymaps).


ΓòÉΓòÉΓòÉ 8. Basic Editing Commands ΓòÉΓòÉΓòÉ

 We now give the basics of how to enter text, make corrections, and save the
text in a file.  If this material is new to you, you might learn it more easily
by running the Emacs learn-by-doing tutorial.  To start the tutorial, type
Control-h t (help-with-tutorial).

 To clear the screen and redisplay, type C-l (recenter).


ΓòÉΓòÉΓòÉ 8.1. Inserting Text ΓòÉΓòÉΓòÉ

 To insert printing characters into the text you are editing, just type them.
This inserts the characters you type into the buffer at the cursor (that is, at
point; see Point).  The cursor moves forward, and any text after the cursor
moves forward too.  If the text in the buffer is `FOOBAR', with the cursor
before the `B', then if you type XX, you get `FOOXXBAR', with the cursor still
before the `B'.

  To delete text you have just inserted, use DEL.  DEL deletes the character
before the cursor (not the one that the cursor is on top of or under; that is
the character after the cursor).  The cursor and all characters after it move
backwards.  Therefore, if you type a printing character and then type DEL, they
cancel out.

  To end a line and start typing a new one, type RET.  This inserts a newline
character in the buffer.  If point is in the middle of a line, RET splits the
line.  Typing DEL when the cursor is at the beginning of a line deletes the
preceding newline, thus joining the line with the preceding line.

 Emacs can split lines automatically when they become too long, if you turn on
a special mode called Auto Fill mode.  See Filling, for how to use Auto Fill
mode.

 Customization information: DEL in most modes runs the command
delete-backward-char; RET runs the command newline, and self-inserting printing
characters run the command self-insert, which inserts whatever character was
typed to invoke it.  Some major modes rebind DEL to other commands.

 Direct insertion works for printing characters and SPC, but other characters
act as editing commands and do not insert themselves.  If you need to insert a
control character or a character whose code is above 200 octal, you must quote
it by typing the character Control-q (quoted-insert) first.  (This character's
name is normally written C-q for short.)  There are two ways to use C-q:

o C-q followed by any non-graphic character (even C-g) inserts that character.

o C-q followed by three octal digits inserts the character with the specified
  character code.

A numeric argument to C-q specifies how many copies of the quoted character
should be inserted (see Arguments).

 If you prefer to have text characters replace (overwrite) existing text rather
than shove it to the right, you can enable Overwrite mode, a minor mode.  See
Minor Modes.


ΓòÉΓòÉΓòÉ 8.2. Changing the Location of Point ΓòÉΓòÉΓòÉ

 To do more than insert characters, you have to know how to move point (see
Point).  The simplest way to do this is with arrow keys or the left mouse
button.

 There are also control and meta characters for cursor motion.  Some are
equivalent to the arrow keys (these date back to the days before terminals had
arrow keys, and are usable on terminals which don't have them).  Others do more
sophisticated things.

C-a
          Move to the beginning of the line (beginning-of-line).

C-e
          Move to the end of the line (end-of-line).

C-f
          Move forward one character (forward-char).

C-b
          Move backward one character (backward-char).

M-f
          Move forward one word (forward-word).

M-b
          Move backward one word (backward-word).

C-n
          Move down one line, vertically (next-line).  This command attempts to
          keep the horizontal position unchanged, so if you start in the middle
          of one line, you end in the middle of the next.  When on the last
          line of text, C-n creates a new line and moves onto it.

C-p
          Move up one line, vertically (previous-line).

M-r
          Move point to left margin, vertically centered in the window
          (move-to-window-line).  Text does not move on the screen.  A numeric
          argument says how many screen lines down from the top of the window
          (zero for the top line).  A negative argument counts lines from the
          bottom (-1 for the bottom line).

M-<
          Move to the top of the buffer (beginning-of-buffer).  With numeric
          argument n, move to n/10 of the way from the top. See Arguments, for
          more information on numeric arguments.

M->
          Move to the end of the buffer (end-of-buffer).

M-x goto-char
          Read a number n and move cursor to character number n. Position 1 is
          the beginning of the buffer.

M-x goto-line
          Read a number n and move cursor to line number n.  Line 1 is the
          beginning of the buffer.

C-x C-n
          Use the current column of point as the semipermanent goal column for
          C-n and C-p (set-goal-column).  Henceforth, those commands always
          move to this column in each line moved into, or as close as possible
          given the contents of the line.  This goal column remains in effect
          until canceled.

C-u C-x C-n
          Cancel the goal column.  Henceforth, C-n and C-p once again try to
          avoid changing the horizontal position, as usual.

 If you set the variable track-eol to a non-nil value, then C-n and C-p when at
the end of the starting line move to the end of another line.  Normally,
track-eol is nil. See Variables, for how to set variables such as track-eol.

 Normally, C-n on the last line of a buffer appends a newline to it.  If the
variable next-line-add-newlines is nil, then C-n gets an error instead (like
C-p on the first line).


ΓòÉΓòÉΓòÉ 8.3. Erasing Text ΓòÉΓòÉΓòÉ

DEL
          Delete the character before the cursor (delete-backward-char).

C-d
          Delete the character after the cursor (delete-char).

C-k
          Kill to the end of the line (kill-line).

M-d
          Kill forward to the end of the next word (kill-word).

M-DEL
          Kill back to the beginning of the previous word (backward-kill-word).

 You already know about the DEL key which deletes the character before the
cursor.  Another key, Control-d (C-d for short), deletes the character after
the cursor, causing the rest of the text on the line to shift left.  If C-d is
typed at the end of a line, that line and the next line are joined together.

 To erase a larger amount of text, use the C-k key, which kills a line at a
time.  If C-k is done at the beginning or middle of a line, it kills all the
text up to the end of the line.  If C-k is done at the end of a line, it joins
that line and the next line.

 If you delete or kill text by mistake, you can use the undo command to get it
back.  See Undo.

 See Killing, for more flexible ways of killing text.


ΓòÉΓòÉΓòÉ 8.4. Files ΓòÉΓòÉΓòÉ

 The commands above are sufficient for creating and altering text in an Emacs
buffer; the more advanced Emacs commands just make things easier. But to keep
any text permanently you must put it in a file.  Files are named units of text
which are stored by the operating system for you to retrieve later by name.  To
look at or use the contents of a file in any way, including editing the file
with Emacs, you must specify the file name.

 Consider a file named `/usr/rms/foo.c'.  In Emacs, to begin editing this file,
type

C-x C-f /usr/rms/foo.c RET

Here the file name is given as an argument to the command C-x C-f (find-file).
That command uses the minibuffer to read the argument, and you type RET to
terminate the argument (see Minibuffer).

 Emacs obeys the command by visiting the file: creating a buffer, copying the
contents of the file into the buffer, and then displaying the buffer for you to
edit.  Then you can make changes, and save the file by typing C-x C-s
(save-buffer).  This makes the changes permanent by copying the altered
contents of the buffer back into the file `/usr/rms/foo.c'.  Until you save,
the changes exist only inside Emacs, and the file `foo.c' is unaltered.

 To create a file, just visit the file with C-x C-f as if it already existed.
This creates an empty buffer in which you can insert the text you want to put
in the file.  The file is actually created when you save this buffer with C-x
C-s.

 Of course, there is a lot more to learn about using files.  See Files.


ΓòÉΓòÉΓòÉ 8.5. Help ΓòÉΓòÉΓòÉ

 If you forget what a key does, you can find out with the Help character, which
is C-h.  Type C-h k followed by the key you want to know about; for example,
C-h k C-n tells you all about what C-n does.  C-h is a prefix key; C-h k is
just one of its subcommands (the command describe-key).  The other subcommands
of C-h provide different kinds of help.  Type C-h three times to get a
description of all the help facilities.  See Help.


ΓòÉΓòÉΓòÉ 8.6. Blank Lines ΓòÉΓòÉΓòÉ

 Here are special commands and techniques for putting in and taking out blank
lines.

C-o
          Insert one or more blank lines after the cursor (open-line).

C-x C-o
          Delete all but one of many consecutive blank lines
          (delete-blank-lines).

 When you want to insert a new line of text before an existing line, you can do
it by typing the new line of text, followed by RET.  However, it may be easier
to see what you are doing if you first make a blank line and then insert the
desired text into it.  This is easy to do using the key C-o (open-line), which
inserts a newline after point but leaves point in front of the newline.  After
C-o, type the text for the new line.  C-o F O O has the same effect as F O O
RET, except for the final location of point.

 You can make several blank lines by typing C-o several times, or by giving it
a numeric argument to tell it how many blank lines to make.  See Arguments, for
how.

 If you have a fill prefix, then C-o command inserts the fill prefix on the new
line, when you use it at the beginning of a line. See Fill Prefix.

 The easy way to get rid of extra blank lines is with the command C-x C-o
(delete-blank-lines).  C-x C-o in a run of several blank lines deletes all but
one of them.  C-x C-o on a solitary blank line deletes that blank line.  When
point is on a nonblank line, C-x C-o deletes any blank lines following that
nonblank line.


ΓòÉΓòÉΓòÉ 8.7. Continuation Lines ΓòÉΓòÉΓòÉ

 If you add too many characters to one line, without breaking it with RET, the
line will grow to occupy two (or more) lines on the screen, with a `\' at the
extreme right margin of all but the last of them. The `\' says that the
following screen line is not really a distinct line in the text, but just the
continuation of a line too long to fit the screen.  Continuation is also called
line wrapping.

 Sometimes it is nice to have Emacs insert newlines automatically when a line
gets too long.  Continuation on the screen does not do that.  Use Auto Fill
mode (see Filling) if that's what you want.

 Instead of continuation, you can display long lines by truncation.  This means
that all the characters that do not fit in the width of the screen or window do
not appear at all.  They remain in the buffer, temporarily invisible.  `$' is
used in the last column instead of `\' to inform you that truncation is in
effect.

 You can turn off continuation for a particular buffer by setting the variable
truncate-lines to non-nil in that buffer. (See Variables.)  Truncation instead
of continuation also happens whenever horizontal scrolling is in use, and
optionally whenever side-by-side windows are in use (see Windows).  Altering
the value of truncate-lines makes it local to the current buffer; until that
time, the default value is in effect.  The default is initially nil.  See
Locals.

 See Display Vars, for additional variables that affect how text is displayed.


ΓòÉΓòÉΓòÉ 8.8. Cursor Position Information ΓòÉΓòÉΓòÉ

 Here are commands to get information about the size and position of parts of
the buffer, and to count lines.

M-x what-page
          Print page number of point, and line number within page.

M-x what-line
          Print line number of point in the buffer.

M-x line-number-mode
          Toggle automatic display of current line number.

M-=
          Print number of lines in the current region (count-lines-region).

C-x =
          Print character code of character after point, character position of
          point, and column of point (what-cursor-position).

 There are two commands for printing the current line number.  M-x what-line
computes the current line number and displays it in the echo area.  M-x
line-number-mode enables display of the current line number in the mode line;
once you turn this on, the number updates as you move point, so it remains
valid all the time.  See Mode Line.

 Line numbers count from one at the beginning of the buffer.  To go to a given
line by number, use M-x goto-line; it prompts you for the line number.

 By contrast, M-x what-page counts pages from the beginning of the file, and
counts lines within the page, printing both numbers. See Pages.

 While on this subject, we might as well mention M-= (count-lines-region),
which prints the number of lines in the region (see Mark). See Pages, for the
command C-x l which counts the lines in the current page.

 The command C-x = (what-cursor-position) can be used to find out the column
that the cursor is in, and other miscellaneous information about point.  It
prints a line in the echo area that looks like this:

Char: x (0170)  point=65986 of 563027(12%)  x=44

(In fact, this is the output produced when point is before the `x=44' in the
example.)

 The two values after `Char:' describe the character following point, first by
showing it and second by giving its octal character code.

 `point=' is followed by the position of point expressed as a character count.
The front of the buffer counts as position 1, one character later as 2, and so
on.  The next, larger number is the total number of characters in the buffer.
Afterward in parentheses comes the position expressed as a percentage of the
total size.

 `x=' is followed by the horizontal position of point, in columns from the left
edge of the window.

 If the buffer has been narrowed, making some of the text at the beginning and
the end temporarily off limits, C-x = prints additional text describing the
currently accessible range.  For example, it might display this:

Char: x (0170)  point=65986 of 563025(12%) <65102 - 68533>  x=44

where the two extra numbers give the smallest and largest character position
that point is allowed to assume.  The characters between those two positions
are the accessible ones.  See Narrowing.

 If point is at the end of the buffer (or the end of the accessible part), C-x
= omits any description of the character after point. The output looks like
this:

point=563026 of 563025(100%)  x=0


ΓòÉΓòÉΓòÉ 8.9. Numeric Arguments ΓòÉΓòÉΓòÉ

 Any Emacs command can be given a numeric argument (also called a prefix
argument).  Some commands interpret the argument as a repetition count.  For
example, giving an argument of ten to the key C-f moves forward ten characters
instead of one.  With these commands, no argument is equivalent to an argument
of one.  Negative arguments tell most such commands to move or act in the
opposite direction.

 If your terminal keyboard has a META key, the easiest way to specify a numeric
argument is to type digits and/or a minus sign while holding down the the META
key.  For example,

M-5 C-n

would move down five lines.  The characters Meta-1, Meta-2, and so on, as well
as Meta--, do this because they are keys bound to commands (digit-argument and
negative-argument) that are defined to contribute to an argument for the next
command.

 Another way of specifying an argument is to use the C-u (universal-argument)
command followed by the digits of the argument. With C-u, you can type the
argument digits without holding down shift keys.  To type a negative argument,
start with a minus sign. Just a minus sign normally means -1.  C-u works on all
terminals.

 C-u followed by a character which is neither a digit nor a minus sign has the
special meaning of ``multiply by four''.  It multiplies the argument for the
next command by four.  C-u twice multiplies it by sixteen.  Thus, C-u C-u C-f
moves forward sixteen characters.  This is a good way to move forward ``fast'',
since it moves about 1/5 of a line in the usual size screen.  Other useful
combinations are C-u C-n, C-u C-u C-n (move down a good fraction of a screen),
C-u C-u C-o (make ``a lot'' of blank lines), and C-u C-k (kill four lines).

 Some commands care only about whether there is an argument, and not about its
value.  For example, the command M-q (fill-paragraph) with no argument fills
text; with an argument, it justifies the text as well. (See Filling, for more
information on M-q.)  Just C-u is a handy way of providing an argument for such
commands.

 Some commands use the value of the argument as a repeat count, but do
something peculiar when there is no argument.  For example, the command C-k
(kill-line) with argument n kills n lines, including their terminating
newlines.  But C-k with no argument is special: it kills the text up to the
next newline, or, if point is right at the end of the line, it kills the
newline itself.  Thus, two C-k commands with no arguments can kill a nonblank
line, just like C-k with an argument of one.  (See Killing, for more
information on C-k.)

 A few commands treat a plain C-u differently from an ordinary argument.  A few
others may treat an argument of just a minus sign differently from an argument
of -1.  These unusual cases will be described when they come up; they are
always for reasons of convenience of use of the individual command.

 You can use a numeric argument to insert multiple copies of a character.  This
is straightforward unless the character is a digit.  To prevent the digit from
becoming part of the argument, type another C-u.  That terminates the argument.
If you then type another digit, then the digit acts as a self-inserting
character and uses the argument as a repeat count.

 We use the term ``prefix argument'' as well as ``numeric argument'' to
emphasize that you type the argument before the command, and to distinguish
these arguments from minibuffer arguments that come after the command.


ΓòÉΓòÉΓòÉ 9. Undoing Changes ΓòÉΓòÉΓòÉ

 Emacs allows all changes made in the text of a buffer to be undone, up to a
certain amount of change.  Each buffer records changes individually, and the
undo command always applies to the current buffer.  Usually each editing
command makes a separate entry in the undo records, but some commands such as
query-replace make many entries, and very simple commands such as
self-inserting characters are often grouped to make undoing less tedious.

C-x u
          Undo one batch of changes---usually, one command worth (undo).

C-_
          The same.

 The command C-x u or C-_ is how you undo.  The first time you give this
command, it undoes the last change.  Point moves back to where it was before
the command that made the change.

 Consecutive repetitions of the C-_ or C-x u commands undo earlier and earlier
changes, back to the limit of what has been recorded.  If all recorded changes
have already been undone, the undo command prints an error message and does
nothing.

 Any command other than an undo command breaks the sequence of undo commands.
Starting at this moment, the previous undo commands are considered ordinary
changes that can themselves be undone.  Thus, you can redo changes you have
undone by typing C-f or any other command that will have no important effect,
and then using more undo commands.

 If you notice that a buffer has been modified accidentally, the easiest way to
recover is to type C-_ repeatedly until the stars disappear from the front of
the mode line.  At this time, all the modifications you made have been
cancelled.  If you do not remember whether you changed the buffer deliberately,
type C-_ once, and when you see the last change you made undone, you will
remember why you made it.  If it was an accident, leave it undone.  If it was
deliberate, redo the change as described in the preceding paragraph.

 Whenever an undo command makes the stars disappear from the mode line, it
means that the buffer contents are the same as they were when the file was last
read in or saved.

 Not all buffers record undo information.  Buffers whose names start with
spaces don't; these buffers are used internally by Emacs and its extensions to
hold text that users don't normally look at or edit.

 You cannot undo mere cursor motion; only changes in the buffer contents save
undo information.  However, some cursor motion commands set the mark, so if you
use these commands from time to time, you can move back to the neighborhoods
you have moved through by popping the mark ring (see Mark Ring).

 When the undo information of a buffer becomes too large, Emacs discards the
oldest undo information from time to time (during garbage collection).  You can
specify how much undo information to keep by setting two variables: undo-limit
and undo-strong-limit. Their values are expressed in units of bytes of space.

 The variable undo-limit sets a soft limit: Emacs keeps undo data for enough
commands to reach this size, and perhaps exceed it, but does not keep data for
any earlier commands beyond that.  Its default value is 20000.  The variable
undo-strong-limit sets a harsher limit: the command which pushes the size past
this amount is itself forgotten.  Its default value is 30000.

 Regardless of the values of those variables, the most recent change is never
discarded, so there is no danger that garbage collection occurring right after
an unintentional large change might prevent you from undoing it.

 The reason the undo command has two keys, C-x u and C-_, set up to run it is
that it is worthy of a single-character key, but on some keyboards it is not
obvious how to type C-_. C-x u is an alternative you can type in the same
fashion on any terminal.


ΓòÉΓòÉΓòÉ 10. The Minibuffer ΓòÉΓòÉΓòÉ

 The minibuffer is the facility used by Emacs commands to read arguments more
complicated than a single number.  Minibuffer arguments can be file names,
buffer names, Lisp function names, Emacs command names, Lisp expressions, and
many other things, depending on the command reading the argument.  You can use
the usual Emacs editing commands in the minibuffer to edit the argument text.

 When the minibuffer is in use, it appears in the echo area, and the terminal's
cursor moves there.  The beginning of the minibuffer line displays a prompt
which says what kind of input you should supply and how it will be used.  Often
this prompt is derived from the name of the command that the argument is for.
The prompt normally ends with a colon.

 Sometimes a default argument appears in parentheses after the colon; it too is
part of the prompt.  The default will be used as the argument value if you
enter an empty argument (e.g., just type RET). For example, commands that read
buffer names always show a default, which is the name of the buffer that will
be used if you type just RET.

 The simplest way to enter a minibuffer argument is to type the text you want,
terminated by RET which exits the minibuffer.  You can get out of the
minibuffer, canceling the command that it was for, by typing C-g.

 Since the minibuffer uses the screen space of the echo area, it can conflict
with other ways Emacs customarily uses the echo area.  Here is how Emacs
handles such conflicts:

o If a command gets an error while you are in the minibuffer, this does not
  cancel the minibuffer.  However, the echo area is needed for the error
  message and therefore the minibuffer itself is hidden for a while.  It comes
  back after a few seconds, or as soon as you type anything.

o If in the minibuffer you use a command whose purpose is to print a message in
  the echo area, such as C-x =, the message is printed normally, and the
  minibuffer is hidden for a while.  It comes back after a few seconds, or as
  soon as you type anything.

o Echoing of keystrokes does not take place while the minibuffer is in use.


ΓòÉΓòÉΓòÉ 10.1. Minibuffers for File Names ΓòÉΓòÉΓòÉ

 Sometimes the minibuffer starts out with text in it.  For example, when you
are supposed to give a file name, the minibuffer starts out containing the
default directory, which ends with a slash.  This is to inform you which
directory the file will be found in if you do not specify a directory.  For
example, the minibuffer might start out with

Find File: /u2/emacs/src/

where `Find File: ' is the prompt.  Typing buffer.c specifies the file
`/u2/emacs/src/buffer.c'.  To find files in nearby directories, use ..; thus,
if you type ../lisp/simple.el, you will get the file named
`/u2/emacs/lisp/simple.el'.  Alternatively, you can kill with M-DEL the
directory names you don't want (see Words).

 You can also type an absolute file name, one starting with a slash or a tilde,
ignoring the default directory.  For example, to find the file `/etc/termcap',
just insert that name, giving these minibuffer contents:

Find File: /u2/emacs/src//etc/termcap

Two slashes in a row are not normally meaningful in a file name, but they are
allowed in GNU Emacs.  They mean, ``ignore everything before the second slash
in the pair.''  Thus, `/u2/emacs/src/' is ignored, and you get the file
`/etc/termcap'.

 If you set insert-default-directory to nil, the default directory is not
inserted in the minibuffer.  This way, the minibuffer starts out empty.  But
the name you type, if relative, is still interpreted with respect to the same
default directory.


ΓòÉΓòÉΓòÉ 10.2. Editing in the Minibuffer ΓòÉΓòÉΓòÉ

 The minibuffer is an Emacs buffer (albeit a peculiar one), and the usual Emacs
commands are available for editing the text of an argument you are entering.

 Since RET in the minibuffer is defined to exit the minibuffer, inserting a
newline into the minibuffer must be done with C-o or with C-q LFD.  (Recall
that a newline is really the LFD character.)

 The minibuffer has its own window which always has space on the screen but
acts as if it were not there when the minibuffer is not in use.  When the
minibuffer is in use, its window is just like the others; you can switch to
another window with C-x o, edit text in other windows and perhaps even visit
more files, before returning to the minibuffer to submit the argument.  You can
kill text in another window, return to the minibuffer window, and then yank the
text to use it in the argument. See Windows.

 There are some restrictions on the use of the minibuffer window, however. You
cannot switch buffers in it---the minibuffer and its window are permanently
attached.  Also, you cannot split or kill the minibuffer window.  But you can
make it taller in the normal fashion with C-x ^.

 If while in the minibuffer you issue a command that displays help text of any
sort in another window, you can use the C-M-v command while in the minibuffer
to scroll the help text.  This lasts until you exit the minibuffer.  This
feature is especially useful if a completing minibuffer gives you a list of
possible completions.  See Other Window.

 You can't use a command that reads a minibuffer argument while you are in the
minibuffer window.  This rule is to prevent recursive minibuffers from
confusing novice users.  If you want to be able to use such commands in the
minibuffer, set the variable enable-recursive-minibuffers to a non-nil value.


ΓòÉΓòÉΓòÉ 10.3. Completion ΓòÉΓòÉΓòÉ

 For certain kinds of arguments, you can use completion to enter the argument
value.  Completion means that you type part of the argument, then Emacs visibly
fills in the rest, or as much as can be determined from the part you have
typed.

 When completion is available, certain keys---TAB, RET, and SPC---are rebound
to complete the text present in the minibuffer into a longer string that it
stands for, by matching it against a set of completion alternatives provided by
the command reading the argument.  ? is defined to display a list of possible
completions of what you have inserted.

 For example, when M-x uses the minibuffer to read the name of a command, it
provides a list of all available Emacs command names to complete against.  The
completion keys match the text in the minibuffer against all the command names,
find any additional name characters implied by the ones already present in the
minibuffer, and add those characters to the ones you have given.  This is what
makes it possible to type M-x ins SPC b RET instead of M-x insert-buffer RET
(for example).

 Case is normally significant in completion, because it is significant in most
of the names that you can complete (buffer names, file names and command
names).  Thus, `fo' does not complete to `Foo'. Completion does ignore case
distinctions for certain arguments in which case does not matter.


ΓòÉΓòÉΓòÉ 10.3.1. Completion Example ΓòÉΓòÉΓòÉ

 A concrete example may help here.  If you type M-x au TAB, the TAB looks for
alternatives (in this case, command names) that start with `au'.  There are
only two: auto-fill-mode and auto-save-mode.  These are the same as far as
auto-, so the `au' in the minibuffer changes to `auto-'.

 If you type TAB again immediately, there are multiple possibilities for the
very next character---it could be `s' or `f'---so no more characters are added;
instead, TAB displays a list of all possible completions in another window.

 If you go on to type f TAB, this TAB sees `auto-f'.  The only command name
starting this way is auto-fill-mode, so completion fills in the rest of that.
You now have `auto-fill-mode' in the minibuffer after typing just au TAB f TAB.
Note that TAB has this effect because in the minibuffer it is bound to the
command minibuffer-complete when completion is available.


ΓòÉΓòÉΓòÉ 10.3.2. Completion Commands ΓòÉΓòÉΓòÉ

 Here is a list of the completion commands defined in the minibuffer when
completion is available.

TAB
          Complete the text in the minibuffer as much as possible
          (minibuffer-complete).

SPC
          Complete the minibuffer text, but don't go beyond one word
          (minibuffer-complete-word).

RET
          Submit the text in the minibuffer as the argument, possibly
          completing first as described below (minibuffer-complete-and-exit).

?
          Print a list of all possible completions of the text in the
          minibuffer (minibuffer-list-completions).

 SPC completes much like TAB, but never goes beyond the next hyphen or space.
If you have `auto-f' in the minibuffer and type SPC, it finds that the
completion is `auto-fill-mode', but it stops completing after `fill-'.  This
gives `auto-fill-'.  Another SPC at this point completes all the way to
`auto-fill-mode'.  SPC in the minibuffer when completion is available runs the
command minibuffer-complete-word.

 There are three different ways that RET can work in completing minibuffers,
depending on how the argument will be used.

o Strict completion is used when it is meaningless to give any argument except
  one of the known alternatives.  For example, when C-x k reads the name of a
  buffer to kill, it is meaningless to give anything but the name of an
  existing buffer.  In strict completion, RET refuses to exit if the text in
  the minibuffer does not complete to an exact match.

o Cautious completion is similar to strict completion, except that RET exits
  only if the text was an exact match already, not needing completion.  If the
  text is not an exact match, RET does not exit, but it does complete the text.
  If it completes to an exact match, a second RET will exit.

  Cautious completion is used for reading file names for files that must
  already exist.

o Permissive completion is used when any string whatever is meaningful, and the
  list of completion alternatives is just a guide. For example, when C-x C-f
  reads the name of a file to visit, any file name is allowed, in case you want
  to create a file.  In permissive completion, RET takes the text in the
  minibuffer exactly as given, without completing it.

 The completion commands display a list of all possible completions in a window
whenever there is more than one possibility for the very next character.  Also,
typing ? explicitly requests such a list.  If the list of completions is long,
you can scroll it with C-M-v (see Other Window).

 When completion is done on file names, certain file names are usually ignored.
The variable completion-ignored-extensions contains a list of strings; a file
whose name ends in any of those strings is ignored as a possible completion.
The standard value of this variable has several elements including ".o",
".elc", ".dvi" and "~".  The effect is that, for example, `foo' can complete to
`foo.c' even though `foo.o' exists as well. However, if all the possible
completions end in ``ignored'' strings, then they are not ignored.  Ignored
extensions do not apply to lists of completions---those always mention all
possible completions.

 Normally, a completion command that finds the next character is undetermined
automatically displays a list of all possible completions.  If the variable
completion-auto-help is set to nil, this does not happen, and you must type ?
to display the possible completions.


ΓòÉΓòÉΓòÉ 10.4. Minibuffer History ΓòÉΓòÉΓòÉ

 Every argument that you enter with the minibuffer is saved on a minibuffer
history list so that you can use it again later in another argument.  Special
commands load the text of an earlier argument in the minibuffer.  They discard
the old minibuffer contents, so you can think of them as moving through the
history of previous arguments.

M-p
          Move to the next earlier argument string saved in the minibuffer
          history (previous-history-element).

M-n
          Move to the next later argument string saved in the minibuffer
          history (next-history-element).

M-r regexp RET
          Move to an earlier saved argument in the minibuffer history that has
          a match for regexp (previous-matching-history-element).

M-s regexp RET
          Move to a later saved argument in the minibuffer history that has a
          match for regexp (next-matching-history-element).

 The simplest way to reuse the saved arguments in the history list is to move
through the history list one element at a time.  While in the minibuffer, type
M-p (previous-history-element) to ``move to'' the next earlier minibuffer
input, and use M-n (next-history-element) to ``move to'' the next later input.

 The previous input that you fetch from the history entirely replaces the
contents of the minibuffer.  To use it as the argument, exit the minibuffer as
usual with RET.  You can also edit the text before you reuse it; this does not
change the history element that you ``moved'' to, but your new argument does go
at the end of the history list in its own right.

 There are also commands to search forward or backward through the history.  As
of this writing, they search for history elements that match a regular
expression that you specify with the minibuffer. M-r
(previous-matching-history-element) searches older elements in the history,
while M-s (next-matching-history-element) searches newer elements.  By special
dispensation, these commands can use the minibuffer to read their arguments
even though you are already in the minibuffer when you issue them.

 All uses of the minibuffer record your input on a history list, but there are
separate history lists for different kinds of input.  For example, there is a
list for file names, used by all the commands that read file names.  There is a
list for arguments of commands like query-replace.  There are also very
specific history lists, such as the one that compile uses for compilation
commands.  Finally, there is one ``miscellaneous'' history list that most
minibuffer arguments use.


ΓòÉΓòÉΓòÉ 10.5. Repeating Minibuffer Commands ΓòÉΓòÉΓòÉ

 Every command that uses the minibuffer at least once is recorded on a special
history list, together with the values of their arguments, so that you can
repeat the entire command.  In particular, every use of M-x is recorded, since
M-x uses the minibuffer to read the command name.

C-x ESC ESC
          Re-execute a recent minibuffer command
          (repeat-complex-command).

M-x list-command-history
          Display the entire command history, showing all the commands C-x ESC
          ESC can repeat, most recent first.

 C-x ESC ESC is used to re-execute a recent minibuffer-using command.  With no
argument, it repeats the last such command.  A numeric argument specifies which
command to repeat; one means the last one, and larger numbers specify earlier
ones.

 C-x ESC ESC works by turning the previous command into a Lisp expression and
then entering a minibuffer initialized with the text for that expression.  If
you type just RET, the command is repeated as before.  You can also change the
command by editing the Lisp expression.  Whatever expression you finally submit
is what will be executed.  The repeated command is added to the front of the
command history unless it is identical to the most recently executed command
already there.

 Even if you don't understand Lisp syntax, it will probably be obvious which
command is displayed for repetition.  If you do not change the text, it will
repeat exactly as before.

 Once inside the minibuffer for C-x ESC ESC, you can use the minibuffer history
commands (M-p, M-n, M-r, M-s; see Minibuffer History) to move through the
history list of saved entire commands.  After finding the desired previous
command, you can edit its expression as usual and then resubmit it by typing
RET as usual.

 The list of previous minibuffer-using commands is stored as a Lisp list in the
variable command-history.  Each element is a Lisp expression which describes
one command and its arguments.  Lisp programs can reexecute a command by
calling eval with the command-history element.


ΓòÉΓòÉΓòÉ 11. Running Commands by Name ΓòÉΓòÉΓòÉ

 The Emacs commands that are used often or that must be quick to type are bound
to keys---short sequences of characters---for convenient use.  Other Emacs
commands that do not need to be brief are not bound to keys; to run them, you
must refer to them by name.

 A command name is, by convention, made up of one or more words, separated by
hyphens; for example, auto-fill-mode or manual-entry.  The use of English words
makes the command name easier to remember than a key made up of obscure
characters, even though it is more characters to type.

 The way to run a command by name is to start with M-x, type the command name,
and finish it with RET.  M-x uses the minibuffer to read the command name.  RET
exits the minibuffer and runs the command.  The string `M-x' appears at the
beginning of the minibuffer as a prompt to remind you to enter the name of a
command to be run.  See Minibuffer, for full information on the features of the
minibuffer.

 You can use completion to enter the command name.  For example, the command
forward-char can be invoked by name by typing

M-x forward-char RET

or

M-x fo TAB c RET

Note that forward-char is the same command that you invoke with the key C-f.
You can run any Emacs command by its name using M-x, whether or not any keys
are bound to it.

 If you type C-g while the command name is being read, you cancel the M-x
command and get out of the minibuffer, ending up at top level.

 To pass a numeric argument to the command you are invoking with M-x, specify
the numeric argument before the M-x.  M-x passes the argument along to the
command it runs.  The argument value appears in the prompt while the command
name is being read.

 Normally, when describing a command that is run by name, we omit the RET that
is needed to terminate the name.  Thus we might speak of M-x auto-fill-mode
rather than M-x auto-fill-mode RET.  We mention the RET only when there is a
need to emphasize its presence, such as when we show the command together with
following arguments.

 M-x is defined to run the command execute-extended-command, which is
responsible for reading the name of another command and invoking it.


ΓòÉΓòÉΓòÉ 12. Help ΓòÉΓòÉΓòÉ

 Emacs provides extensive help features accessible through a single character,
C-h.  C-h is a prefix key that is used only for documentation-printing
commands.  The characters that you can type after C-h are called help options.
One help option is C-h; that is how you ask for help about using C-h.

 C-h C-h prints a list of the possible help options, and then asks you to go
ahead and type the option.  It prompts with this string:

a b c f i k l m n p s t v w C-c C-d C-n C-w.  Type C-h for more help:

You should then type one of those characters.

 Typing a third C-h displays a description of what the options mean; it still
waits for you to type an option.  To cancel, type C-g.


ΓòÉΓòÉΓòÉ 12.1. Help Summary ΓòÉΓòÉΓòÉ

 Here is a summary of the defined help commands.

C-h a regexp RET
          Display list of commands whose names match regexp (command-apropos).

C-h b
          Display a table of all key bindings in effect now, in this order:
          minor mode bindings, major mode bindings, and global bindings
          (describe-bindings).

C-h c key
          Print the name of the command that key runs (describe-key-briefly).
          c is for `character'.  For more extensive information on key, use C-h
          k.

C-h f function RET
          Display documentation on the Lisp function named function
          (describe-function).  Since commands are Lisp functions, a command
          name may be used.

C-h i
          Run Info, the program for browsing documentation files (info). The
          complete Emacs manual is available on-line in Info.

C-h k key
          Display name and documentation of the command that key runs
          (describe-key).

C-h l
          Display a description of the last 100 characters you typed
          (view-lossage).

C-h m
          Display documentation of the current major mode (describe-mode).

C-h n
          Display documentation of Emacs changes, most recent first
          (view-emacs-news).

C-h p
          Find packages by topic keyword (finder-by-keyword).

C-h s
          Display current contents of the syntax table, plus an explanation of
          what they mean (describe-syntax).  See Syntax.

C-h t
          Enter the Emacs interactive tutorial (help-with-tutorial).

C-h v var RET
          Display the documentation of the Lisp variable var
          (describe-variable).

C-h w command RET
          Print which keys run the command named command (where-is).

C-h C-f function RET
          Enter Info and go to the node documenting the Emacs function function
          (info-goto-emacs-command-node).

C-h C-k key
          Enter Info and go to the node where the key sequence key is
          documented (info-goto-emacs-key-command-node).


ΓòÉΓòÉΓòÉ 12.2. Documentation for a Key ΓòÉΓòÉΓòÉ

 The most basic C-h options are C-h c (describe-key-briefly) and C-h k
(describe-key). C-h c key prints in the echo area the name of the command that
key is bound to.  For example, C-h c C-f prints `forward-char'.  Since command
names are chosen to describe what the commands do, this is a good way to get a
very brief description of what key does.

 C-h k key is similar but gives more information: it displays the documentation
string of the command as well as its name. This is too big for the echo area,
so a window is used for the display.

 C-h c and C-h k work for any sort of key sequences, including function keys
and mouse events.


ΓòÉΓòÉΓòÉ 12.3. Help by Command or Variable Name ΓòÉΓòÉΓòÉ

 C-h f (describe-function) reads the name of a Lisp function using the
minibuffer, then displays that function's documentation string in a window.
Since commands are Lisp functions, you can use this to get the documentation of
a command that is known by name.  For example,

C-h f auto-fill-mode RET

displays the documentation of auto-fill-mode.  This is the only way to get the
documentation of a command that is not bound to any key (one which you would
normally run using M-x).

 C-h f is also useful for Lisp functions that you are planning to use in a Lisp
program.  For example, if you have just written the expression (make-vector
len) and want to check that you are using make-vector properly, type C-h f
make-vector RET. Because C-h f allows all function names, not just command
names, you may find that some of your favorite abbreviations that work in M-x
don't work in C-h f.  An abbreviation may be unique among command names yet
fail to be unique when other function names are allowed.

 The function name for C-h f to describe has a default which is used if you
type RET leaving the minibuffer empty.  The default is the function called by
the innermost Lisp expression in the buffer around point, provided that is a
valid, defined Lisp function name.  For example, if point is located following
the text `(make-vector (car x)', the innermost list containing point is the one
that starts with `(make-vector', so the default is to describe the function
make-vector.

 C-h f is often useful just to verify that you have the right spelling for the
function name.  If C-h f mentions a default in the prompt, you have typed the
name of a defined Lisp function.  If that is all you want to know, just type
C-g to cancel the C-h f command, then go on editing.

 C-h w command RET tells you what keys are bound to command.  It prints a list
of the keys in the echo area.  If it says the command is not on any key, you
must use M-x to run it.

 C-h v (describe-variable) is like C-h f but describes Lisp variables instead
of Lisp functions.  Its default is the Lisp symbol around or before point, but
only if that is the name of a known Lisp variable.  See Variables.


ΓòÉΓòÉΓòÉ 12.4. Apropos ΓòÉΓòÉΓòÉ

 A more sophisticated sort of question to ask is, ``What are the commands for
working with files?''  To ask this question, type C-h a file RET, which
displays a list of all command names that contain `file', including copy-file,
find-file, and so on.  With each command name appears a brief description of
how to use the command, and what keys you can currently invoke it with.  For
example, it would say that you can invoke find-file by typing C-x C-f.  The a
in C-h a stands for `Apropos'; C-h a runs the command command-apropos.

 Because C-h a looks only for functions whose names contain the string which
you specify, you must use ingenuity in choosing the string.  If you are looking
for commands for killing backwards and C-h a kill-backwards RET doesn't reveal
any, don't give up. Try just kill, or just backwards, or just back.  Be
persistent.  Also note that you can use a regular expression as the argument,
for more flexibility (see Regexps).

 Here is a set of arguments to give to C-h a that covers many classes of Emacs
commands, since there are strong conventions for naming the standard Emacs
commands.  By giving you a feel for the naming conventions, this set should
also serve to aid you in developing a technique for picking apropos strings.

char, line, word, sentence, paragraph, region, page, sexp, list, defun, rect,
buffer, frame, window, file, dir, register, mode, beginning, end, forward,
backward, next, previous, up, down, search, goto, kill, delete, mark, insert,
yank, fill, indent, case, change, set, what, list, find, view, describe.

 To list all Lisp symbols that contain a match for a regexp, not just the ones
that are defined as commands, use the command M-x apropos instead of C-h a.
This command does not check key bindings by default; specify a numeric argument
if you want it to check them.

 The super-apropos command is like apropos except that it searches
documentation strings as well as symbol names for matches for the specified
regular expression.


ΓòÉΓòÉΓòÉ 12.5. Keyword Search for Lisp Libraries ΓòÉΓòÉΓòÉ

The C-h p command lets you search the standard Emacs Lisp libraries by topic
keywords.  Here is a partial list of keywords you can use:

`abbrev'
          Abbreviation handling, typing shortcuts, macros.

`bib'
          Support for the bibliography processor bib.

`c'
          C and C++ language support.

`calendar'
          Calendar and time management support.

`comm'
          Communications, networking, remote access to files.

`docs'
          Support for Emacs documentation.

`emulations'
          Emulations of other editors.

`extensions'
          Emacs Lisp language extensions.

`faces'
          Support for using faces (fonts and colors; see Faces).

`games'
          Games, jokes and amusements.

`hardware'
          Support for interfacing with exotic hardware.

`help'
          Support for on-line help systems.

`i18n'
          Internationalization and alternate character-set support.

`internal'
          Code for Emacs internals, build process, defaults.

`languages'
          Specialized modes for editing programming languages.

`lisp'
          Support for using Lisp (including Emacs Lisp).

`local'
          Libraries local to your site.

`maint'
          Maintenance aids for the Emacs development group.

`mail'
          Modes for electronic-mail handling.

`news'
          Support for netnews reading and posting.

`non-text'
          Support for editing files that are not ordinary text.

`processes'
          Process, subshell, compilation, and job control support.

`terminals'
          Support for terminal types.

`tex'
          Support for the TeX formatter.

`tools'
          Programming tools.

`unix'
          Front-ends/assistants for, or emulators of, Unix features.

`vms'
          Support code for VMS.

`wp'
          Word processing.


ΓòÉΓòÉΓòÉ 12.6. Other Help Commands ΓòÉΓòÉΓòÉ

 C-h i (info) runs the Info program, which is used for browsing through
structured documentation files.  The entire Emacs manual is available within
Info.  Eventually all the documentation of the GNU system will be available.
Type h after entering Info to run a tutorial on using Info.

 There are two special help commands for accessing Emacs documentation through
Info.  C-h C-f function RET enters Info and goes straight to the documentation
of the Emacs function function.  C-h C-k key enters Info and goes straight to
the documentation of the key key.  These two keys run the commands
Info-goto-emacs-command-node and Info-goto-emacs-key-command-node.

 If something surprising happens, and you are not sure what commands you typed,
use C-h l (view-lossage).  C-h l prints the last 100 command characters you
typed in.  If you see commands that you don't know, you can use C-h c to find
out what they do.

 Emacs has numerous major modes, each of which redefines a few keys and makes a
few other changes in how editing works.  C-h m (describe-mode) prints
documentation on the current major mode, which normally describes all the
commands that are changed in this mode.

 C-h b (describe-bindings) and C-h s (describe-syntax) present other
information about the current Emacs mode.  C-h b displays a list of all the key
bindings now in effect; the local bindings defined by the current minor modes
first, then the local bindings defined by the current major mode, and finally
the global bindings (see Key Bindings).  C-h s displays the contents of the
syntax table, with explanations of each character's syntax (see Syntax).

 You can get a similar list for a particular prefix key by typing C-h after the
prefix key.  (There are a few prefix keys for which this does not work---those
that provide their own bindings for C-h.  One of these is ESC, because ESC C-h
is actually C-M-h, which marks a defun.)

 The other C-h options display various files of useful information. C-h C-w
displays the full details on the complete absence of warranty for GNU Emacs.
C-h n (view-emacs-news) displays the file `emacs/etc/NEWS', which contains
documentation on Emacs changes arranged chronologically.  C-h t
(help-with-tutorial) displays the learn-by-doing Emacs tutorial.  C-h C-c
(describe-copying) displays the file `emacs/etc/COPYING', which tells you the
conditions you must obey in distributing copies of Emacs.  C-h C-d
(describe-distribution) displays the file `emacs/etc/DISTRIB', which tells you
how you can order a copy of the latest version of Emacs.


ΓòÉΓòÉΓòÉ 13. The Mark and the Region ΓòÉΓòÉΓòÉ

 There are many Emacs commands which operate on an arbitrary contiguous part of
the current buffer.  To specify the text for such a command to operate on, you
set the mark at one end of it, and move point to the other end.  The text
between point and the mark is called the region. You can move point or the mark
to adjust the boundaries of the region.  It doesn't matter which one is set
first chronologically, or which one comes earlier in the text.

 Once the mark has been set, it remains where you put it until it is set again
at another place.  The mark remains fixed with respect to the preceding
character if text is inserted or deleted in the buffer.  Each Emacs buffer has
its own mark, so that when you return to a buffer that had been selected
previously, it has the same mark it had before.

 Many commands that insert text, such as C-y (yank) and M-x insert-buffer,
position point and the mark at opposite ends of the inserted text, so that the
region contains the text just inserted.

 Aside from delimiting the region, the mark is also useful for remembering a
spot that you may want to go back to.  To make this feature more useful, each
buffer remembers 16 previous locations of the mark in the mark ring.


ΓòÉΓòÉΓòÉ 13.1. Setting the Mark ΓòÉΓòÉΓòÉ

 Here are some commands for setting the mark:

C-SPC
          Set the mark where point is (set-mark-command).

C-@
          The same.

C-x C-x
          Interchange mark and point (exchange-point-and-mark).

 For example, suppose you wish to convert part of the buffer to all upper-case,
using the C-x C-u (upcase-region) command which operates on the text in the
region.  You can first go to the beginning of the text to be capitalized, type
C-SPC to put the mark there, move to the end, and then type C-x C-u.  Or, you
can set the mark at the end of the text, move to the beginning, and then type
C-x C-u.

 The most common way to set the mark is with the C-SPC command
(set-mark-command).  This sets the mark where point is.  Then you can move
point away, leaving the mark behind.

 Ordinary terminals have only one cursor, so there is no way for Emacs to show
you where the mark is located.  You have to remember.  The usual solution to
this problem is to set the mark and then use it soon, before you forget where
it is.  Alternatively, you can see where the mark is with the command C-x C-x
(exchange-point-and-mark) which puts the mark where point was and point where
the mark was.  The extent of the region is unchanged, but the cursor and point
are now at the previous position of the mark.

 C-x C-x is also useful when you are satisfied with the position of point but
want to move the mark; do C-x C-x to put point at that end of the region, and
then move it.  A second use of C-x C-x, if necessary, puts the mark at the new
position with point back at its original position.

 There is no such character as C-SPC in ASCII; when you type SPC while holding
down CTRL, what you get on most ordinary terminals is the character C-@.  This
key is actually bound to set-mark-command.  But unless you are unlucky enough
to have a terminal where typing C-SPC does not produce C-@, you might as well
think of this character as C-SPC.  Under X, C-SPC is actually a distinct
character, but its binding is still set-mark-command.


ΓòÉΓòÉΓòÉ 13.2. Transient Mark Mode ΓòÉΓòÉΓòÉ

 Many Emacs commands move the mark and invisibly set new regions. This means
that there is almost always some region that you can act on.  This is
convenient, provided you get used to keeping track of the mark's position.

 Some people prefer a more rigid mode of operation in which you must set up a
region for each command that uses one---in which the region ``lasts'' only
temporarily.  This is called Transient Mark mode.  It is particularly
well-suited to window systems such as X, since Emacs can highlight the region
when it is active.

 To enable Transient Mark mode, type M-x transient-mark-mode. This command
toggles the mode, so you can issue it again to return to the normal Emacs way
of handling the mark and the region.

 Here are the details of Transient Mark mode:

o To set the mark, type C-SPC (set-mark-command). This makes the mark active;
  as you move point, you will see the region highlighting change in extent.

o On a window system, an easy way to select a region is to press the button
  Mouse-1 (normally the left button) at one end of it, drag the mouse to the
  other end, and then release the button.

o When the mark is active, you can execute any commands you want on the region,
  such as killing, indentation, or writing to a file.

o Any change to the buffer, such as inserting or deleting a character,
  deactivates the mark.  This means any subsequent command that operates on a
  region will get an error and refuse to operate.  You can make the region
  active again by typing C-x C-x.

o Commands like M-> that ``leave the mark behind'' do not activate the new
  mark.  it.  You can activate the new region by executing C-x C-x
  (exchange-point-and-mark).

o Quitting with C-g deactivates the mark.

 Transient Mark mode is also sometimes known as ``Zmacs mode'' because the
Zmacs editor on the MIT Lisp Machine handled the mark in a similar way.

 When multiple windows show the same buffer, they can have different regions,
because they can have different values of point.  In Transient Mark mode, each
window highlights its own region.  The part that is highlighted in the selected
window is the region that editing commands use.  See Windows.


ΓòÉΓòÉΓòÉ 13.3. Operating on the Region ΓòÉΓòÉΓòÉ

 Once you have set up a region and the mark is active, you can do many things
to the text in it:

o Kill it with C-w (see Killing).

o Save it in a register with C-x r s (see Registers).

o Save it in a buffer or a file (see Accumulating Text).

o Convert case with C-x C-l or C-x C-u (see Case).

o Indent it with C-x TAB or C-M-\ (see Indentation).

o Fill it as text with M-x fill-region (see Filling).

o Print hardcopy with M-x print-region (see Hardcopy).

o Evaluate it as Lisp code with M-x eval-region (see Lisp Eval).

 Most commands that operate on the text in the region have the word region in
their names.


ΓòÉΓòÉΓòÉ 13.4. Commands to Mark Textual Objects ΓòÉΓòÉΓòÉ

 Here are the commands for placing point and the mark around a textual object
such as a word, list, paragraph or page.

M-@
          Set mark after end of next word (mark-word).  This command and the
          following one do not move point.

C-M-@
          Set mark after end of next Lisp expression (mark-sexp).

M-h
          Put region around current paragraph (mark-paragraph).

C-M-h
          Put region around current Lisp defun (mark-defun).

C-x h
          Put region around entire buffer (mark-whole-buffer).

C-x C-p
          Put region around current page (mark-page).

M-@ (mark-word) puts the mark at the end of the next word, while C-M-@
(mark-sexp) puts it at the end of the next Lisp expression.  These commands
handle arguments just like M-f and C-M-f.

  Other commands set both point and mark, to delimit an object in the buffer.
For example, M-h (mark-paragraph) moves point to the beginning of the paragraph
that surrounds or follows point, and puts the mark at the end of that paragraph
(see Paragraphs).  It prepares the region so you can indent, case-convert, or
kill a whole paragraph.

 C-M-h (mark-defun) similarly puts point before and the mark after the current
or following defun (see Defuns).  C-x C-p (mark-page) puts point before the
current page, and mark at the end (see Pages).  The mark goes after the
terminating page delimiter (to include it), while point goes after the
preceding page delimiter (to exclude it).  A numeric argument specifies a later
page (if positive) or an earlier page (if negative) instead of the current
page.

 Finally, C-x h (mark-whole-buffer) sets up the entire buffer as the region, by
putting point at the beginning and the mark at the end.


ΓòÉΓòÉΓòÉ 13.5. The Mark Ring ΓòÉΓòÉΓòÉ

 Aside from delimiting the region, the mark is also useful for remembering a
spot that you may want to go back to.  To make this feature more useful, each
buffer remembers 16 previous locations of the mark, in the mark ring.  Commands
that set the mark also push the old mark onto this ring.  To return to a marked
location, use C-u C-SPC (or C-u C-@); this is the command set-mark-command
given a numeric argument.  It moves point to where the mark was, and restores
the mark from the ring of former marks.  Thus, repeated use of this command
moves point to all of the old marks on the ring, one by one.  The mark
positions you move through in this way are not lost; they go to the end of the
ring.

 Each buffer has its own mark ring.  All editing commands use the current
buffer's mark ring.  In particular, C-u C-SPC always stays in the same buffer.

 Many commands that can move long distances, such as M-< (beginning-of-buffer),
start by setting the mark and saving the old mark on the mark ring.  This is to
make it easier for you to move back later.  Searches set the mark if they move
point.  You can tell when a command sets the mark because it displays `Mark
Set' in the echo area.

 If you want to move back to the same place over and over, the mark ring may
not be convenient enough.  If so, you can record the position in a register for
later retrieval (see RegPos).

 The variable mark-ring-max specifies the maximum number of entries to keep in
the mark ring.  If that many entries exist and another one is pushed, the last
one in the list is discarded.  Repeating C-u C-SPC circulates through the
positions currently in the ring.

 The variable mark-ring holds the mark ring itself, as a list of marker objects
in the order most recent first.  This variable is local in every buffer.


ΓòÉΓòÉΓòÉ 13.6. Deletion and Killing ΓòÉΓòÉΓòÉ

 Most commands which erase text from the buffer save it in the kill ring so
that you can move or copy it to other parts of the buffer. These commands are
known as kill commands.  The rest of the commands that erase text do not save
it in the kill ring; they are known as delete commands.  (This distinction is
made only for erasure of text in the buffer.)  If you do a kill or delete
command by mistake, you can use the C-x u (undo) command to undo it (see Undo).

 The delete commands include C-d (delete-char) and DEL (delete-backward-char),
which delete only one character at a time, and those commands that delete only
spaces or newlines.  Commands that can destroy significant amounts of
nontrivial data generally kill. The commands' names and individual descriptions
use the words `kill' and `delete' to say which they do.

 You can use kill commands in read-only buffers.  They don't actually change
the buffer, and they beep to warn you of that, but they do copy the text you
tried to kill into the kill ring, so you can yank it into other buffers.


ΓòÉΓòÉΓòÉ 13.6.1. Deletion ΓòÉΓòÉΓòÉ

C-d
          Delete next character (delete-char).

DEL
          Delete previous character (delete-backward-char).

M-\
          Delete spaces and tabs around point (delete-horizontal-space).

M-SPC
          Delete spaces and tabs around point, leaving one space
          (just-one-space).

C-x C-o
          Delete blank lines around the current line (delete-blank-lines).

M-^
          Join two lines by deleting the intervening newline, along with any
          indentation following it (delete-indentation).

 The most basic delete commands are C-d (delete-char) and DEL
(delete-backward-char).  C-d deletes the character after point, the one the
cursor is ``on top of''.  This doesn't move point.  DEL deletes the character
before the cursor, and moves point back.  You can delete newlines like any
other characters in the buffer; deleting a newline joins two lines.  Actually,
C-d and DEL aren't always delete commands; when given arguments, they kill
instead, since they can erase more than one character this way.

 The other delete commands are those which delete only whitespace characters:
spaces, tabs and newlines.  M-\ (delete-horizontal-space) deletes all the
spaces and tab characters before and after point.  M-SPC (just-one-space) does
likewise but leaves a single space after point, regardless of the number of
spaces that existed previously (even zero).

 C-x C-o (delete-blank-lines) deletes all blank lines after the current line.
If the current line is blank, it deletes all blank lines preceding the current
line as well (leaving one blank line, the current line).

 M-^ (delete-indentation) joins the current line and the previous line, by
deleting a newline and all surrounding spaces, usually leaving a single space.
See Indentation.


ΓòÉΓòÉΓòÉ 13.6.2. Killing by Lines ΓòÉΓòÉΓòÉ

C-k
          Kill rest of line or one or more lines (kill-line).

 The simplest kill command is C-k.  If given at the beginning of a line, it
kills all the text on the line, leaving it blank.  When used on a blank line,
it kills the whole line including its newline.  To kill an entire non-blank
line, go to the beginning and type C-k twice.

 More generally, C-k kills from point up to the end of the line, unless it is
at the end of a line.  In that case it kills the newline following point, thus
merging the next line into the current one. Spaces and tabs that you can't see
at the end of the line are ignored when deciding which case applies, so if
point appears to be at the end of the line, you can be sure C-k will kill the
newline.

 When C-k is given a positive argument, it kills that many lines and the
newlines that follow them (however, text on the current line before point is
spared).  With a negative argument -n, it kills n lines preceding the current
line (together with the text on the current line before point).  Thus, C-u - 2
C-k at the front of a line kills the two previous lines.

 C-k with an argument of zero kills the text before point on the current line.

 If the variable kill-whole-line is non-nil, C-k at the very beginning of a
line kills the entire line including the following newline.  This variable is
normally nil.


ΓòÉΓòÉΓòÉ 13.6.3. Other Kill Commands ΓòÉΓòÉΓòÉ

C-w
          Kill region (from point to the mark) (kill-region).

M-d
          Kill word (kill-word).  See Words.

M-DEL
          Kill word backwards (backward-kill-word).

C-x DEL
          Kill back to beginning of sentence (backward-kill-sentence). See
          Sentences.

M-k
          Kill to end of sentence (kill-sentence).

C-M-k
          Kill sexp (kill-sexp).  See Lists.

M-z char
          Kill through the next occurrence of char (zap-to-char).

 A kill command which is very general is C-w (kill-region), which kills
everything between point and the mark.  With this command, you can kill any
contiguous sequence of characters, if you first set the region around them.

 A convenient way of killing is combined with searching: M-z (zap-to-char)
reads a character and kills from point up to (and including) the next
occurrence of that character in the buffer.  A numeric argument acts as a
repeat count.  A negative argument means to search backward and kill text
before point.

 Other syntactic units can be killed: words, with M-DEL and M-d (see Words);
sexps, with C-M-k (see Lists); and sentences, with C-x DEL and M-k (see
Sentences).


ΓòÉΓòÉΓòÉ 13.7. Yanking ΓòÉΓòÉΓòÉ

 Yanking means reinserting text previously killed.  This is what some systems
call ``pasting''.  The usual way to move or copy text is to kill it and then
yank it elsewhere one or more times.

C-y
          Yank last killed text (yank).

M-y
          Replace text just yanked with an earlier batch of killed text
          (yank-pop).

M-w
          Save region as last killed text without actually killing it
          (kill-ring-save).

C-M-w
          Append next kill to last batch of killed text (append-next-kill).


ΓòÉΓòÉΓòÉ 13.7.1. The Kill Ring ΓòÉΓòÉΓòÉ

 All killed text is recorded in the kill ring, a list of blocks of text that
have been killed.  There is only one kill ring, used in all buffers, so you can
kill text in one buffer and yank it in another buffer. This is the usual way to
move text from one file to another. (See Accumulating Text, for some other
ways.)

 The command C-y (yank) reinserts the text of the most recent kill.  It leaves
the cursor at the end of the text.  It sets the mark at the beginning of the
text.  See Mark.

 C-u C-y leaves the cursor in front of the text, and sets the mark after it.
This is only if the argument is specified with just a C-u, precisely.  Any
other sort of argument, including C-u and digits, specifies an earlier kill to
yank (see Earlier Kills).

 If you wish to copy a block of text, you might want to use M-w
(kill-ring-save), which copies the region into the kill ring without removing
it from the buffer.  This is approximately equivalent to C-w followed by C-x u,
except that M-w does not alter the undo history and does not temporarily change
the screen.


ΓòÉΓòÉΓòÉ 13.7.2. Appending Kills ΓòÉΓòÉΓòÉ

 Normally, each kill command pushes a new entry onto the kill ring. However,
two or more kill commands in a row combine their text into a single entry, so
that a single C-y gets it all back as it was before it was killed.

 Thus, if you want to yank text as a unit, you need not kill all of it with one
command; you can keep killing line after line, or word after word, until you
have killed it all, and you can still get it all back at once.

 Commands that kill forward from point add onto the end of the previous killed
text.  Commands that kill backward from point add text onto the beginning.
This way, any sequence of mixed forward and backward kill commands puts all the
killed text into one entry without rearrangement. Numeric arguments do not
break the sequence of appending kills.  For example, suppose the buffer
contains

This is a line -!-of sample text.

with point as shown.  If you type M-d M-DEL M-d M-DEL, killing alternately
forward and backward, you end up with `a line of sample' as one entry in the
kill ring, and `This is text.' in the buffer.  (Note the double space, which
you can clean up with M-SPC or M-q.)

 Another way to kill the same text is to move back two words with M-b M-b, then
kill all four words forward with C-u M-d. This produces exactly the same
results in the buffer and in the kill ring.  M-f M-f C-u M-DEL kills the same
text, all going backward; once again, the result is the same.  The text in the
kill ring entry always has the same order that it had in the buffer before you
killed it.

 If a kill command is separated from the last kill command by other commands
(not just numeric arguments), it starts a new entry on the kill ring.  But you
can force it to append by first typing the command C-M-w (append-next-kill)
right before it.  The C-M-w tells the following command, if it is a kill
command, to append the text it kills to the last killed text, instead of
starting a new entry.  With C-M-w, you can kill several separated pieces of
text and accumulate them to be yanked back in one place.


ΓòÉΓòÉΓòÉ 13.7.3. Yanking Earlier Kills ΓòÉΓòÉΓòÉ

 To recover killed text that is no longer the most recent kill, use the M-y
command (yank-pop).  It takes the text previously yanked and replaces it with
the text from an earlier kill.  So, to recover the text of the next-to-the-last
kill, first use C-y to yank the last kill, and then use M-y to replace it with
the previous kill.  M-y is allowed only after a C-y or another M-y.

 You can understand M-y in terms of a ``last yank'' pointer which points at an
entry in the kill ring.  Each time you kill, the ``last yank'' pointer moves to
the newly made entry at the front of the ring. C-y yanks the entry which the
``last yank'' pointer points to. M-y moves the ``last yank'' pointer to a
different entry, and the text in the buffer changes to match.  Enough M-y
commands can move the pointer to any entry in the ring, so you can get any
entry into the buffer.  Eventually the pointer reaches the end of the ring; the
next M-y moves it to the first entry again.

 M-y moves the ``last yank'' pointer around the ring, but it does not change
the order of the entries in the ring, which always runs from the most recent
kill at the front to the oldest one still remembered.

 M-y can take a numeric argument, which tells it how many entries to advance
the ``last yank'' pointer by.  A negative argument moves the pointer toward the
front of the ring; from the front of the ring, it moves ``around'' to the last
entry and continues forward from there.

 Once the text you are looking for is brought into the buffer, you can stop
doing M-y commands and it will stay there.  It's just a copy of the kill ring
entry, so editing it in the buffer does not change what's in the ring.  As long
as no new killing is done, the ``last yank'' pointer remains at the same place
in the kill ring, so repeating C-y will yank another copy of the same previous
kill.

 If you know how many M-y commands it would take to find the text you want, you
can yank that text in one step using C-y with a numeric argument.  C-y with an
argument restores the text the specified number of entries back in the kill
ring.  Thus, C-u 2 C-y gets the next to the last block of killed text.  It is
equivalent to C-y M-y.  C-y with a numeric argument starts counting from the
``last yank'' pointer, and sets the ``last yank'' pointer to the entry that it
yanks.

 The length of the kill ring is controlled by the variable kill-ring-max; no
more than that many blocks of killed text are saved.

 The actual contents of the kill ring are stored in a variable named kill-ring;
you can view the entire contents of the kill ring with the command C-h v
kill-ring.


ΓòÉΓòÉΓòÉ 13.8. Accumulating Text ΓòÉΓòÉΓòÉ

 Usually we copy or move text by killing it and yanking it, but there are other
methods convenient for copying one block of text in many places, or for copying
many scattered blocks of text into one place.  To copy one block to many
places, store it in a register (see Registers).  Here we describe the commands
to accumulate scattered pieces of text into a buffer or into a file.

M-x append-to-buffer
          Append region to contents of specified buffer.

M-x prepend-to-buffer
          Prepend region to contents of specified buffer.

M-x copy-to-buffer
          Copy region into specified buffer, deleting that buffer's old
          contents.

M-x insert-buffer
          Insert contents of specified buffer into current buffer at point.

M-x append-to-file
          Append region to contents of specified file, at the end.

 To accumulate text into a buffer, use M-x append-to-buffer. This reads a
buffer name, them inserts a copy of the region into the buffer specified.  If
you specify a nonexistent buffer, append-to-buffer creates the buffer.  The
text is inserted wherever point is in that buffer.  If you have been using the
buffer for editing, the copied text goes into the middle of the text of the
buffer, wherever point happens to be in it.

 Point in that buffer is left at the end of the copied text, so successive uses
of append-to-buffer accumulate the text in the specified buffer in the same
order as they were copied.  Strictly speaking, append-to-buffer does not always
append to the text already in the buffer---only if point in that buffer is at
the end. However, if append-to-buffer is the only command you use to alter a
buffer, then point is always at the end.

 M-x prepend-to-buffer is just like append-to-buffer except that point in the
other buffer is left before the copied text, so successive prependings add text
in reverse order.  M-x copy-to-buffer is similar except that any existing text
in the other buffer is deleted, so the buffer is left containing just the text
newly copied into it.

 To retrieve the accumulated text from another buffer, use M-x insert-buffer;
this too takes buffername as an argument.  It inserts a copy of the text in
buffer buffername into the selected buffer.  You can alternatively select the
other buffer for editing, then optionally move text from it by killing.  See
Buffers, for background information on buffers.

 Instead of accumulating text within Emacs, in a buffer, you can append text
directly into a file with M-x append-to-file, which takes filename as an
argument.  It adds the text of the region to the end of the specified file.
The file is changed immediately on disk.

 You should use append-to-file only with files that are not being visited in
Emacs.  Using it on a file that you are editing in Emacs would change the file
behind Emacs's back, which can lead to losing some of your editing.


ΓòÉΓòÉΓòÉ 13.9. Rectangles ΓòÉΓòÉΓòÉ

 The rectangle commands operate on rectangular areas of the text: all the
characters between a certain pair of columns, in a certain range of lines.
Commands are provided to kill rectangles, yank killed rectangles, clear them
out, fill them with blanks or text, or delete them. Rectangle commands are
useful with text in multicolumn formats, and for changing text into or out of
such formats.

 When you must specify a rectangle for a command to work on, you do it by
putting the mark at one corner and point at the opposite corner.  The rectangle
thus specified is called the region-rectangle because you control it in about
the same way the region is controlled.  But remember that a given combination
of point and mark values can be interpreted either as a region or as a
rectangle, depending on the command that uses them.

 If point and the mark are in the same column, the rectangle they delimit is
empty.  If they are in the same line, the rectangle is one line high.  This
asymmetry between lines and columns comes about because point (and likewise the
mark) is between two columns, but within a line.

C-x r k
          Kill the text of the region-rectangle, saving its contents as the
          ``last killed rectangle'' (kill-rectangle).

C-x r y
          Yank the last killed rectangle with its upper left corner at point
          (yank-rectangle).

C-x r o
          Insert blank space to fill the space of the region-rectangle
          (open-rectangle).  This pushes the previous contents of the
          region-rectangle rightward.

M-x delete-rectangle
          Delete the text of the region-rectangle without saving it in any
          special way.

M-x clear-rectangle
          Clear the region-rectangle by replacing its contents with spaces.

M-x string-rectangle RET string RET
          Insert string on each line of the region-rectangle.

 The rectangle operations fall into two classes: commands deleting and
inserting rectangles, and commands for blank rectangles.

 There are two ways to get rid of the text in a rectangle: you can discard the
text (delete it) or save it as the ``last killed'' rectangle.  The commands for
these two ways are M-x delete-rectangle and C-x r k (kill-rectangle).  In
either case, the portion of each line that falls inside the rectangle's
boundaries is deleted, causing following text (if any) on the line to move left
into the gap.

 Note that ``killing'' a rectangle is not killing in the usual sense; the
rectangle is not stored in the kill ring, but in a special place that can only
record the most recent rectangle killed.  This is because yanking a rectangle
is so different from yanking linear text that different yank commands have to
be used and yank-popping is hard to make sense of.

 Yanking a rectangle is the opposite of killing one.  Point specifies where to
put the rectangle's upper left corner.  The rectangle's first line is inserted
there, the rectangle's second line is inserted at a point one line vertically
down, and so on.  The number of lines affected is determined by the height of
the saved rectangle.

 To yank the last killed rectangle, type C-x r y (yank-rectangle).  This can be
used to convert single-column lists into double-column lists; kill the second
half of the list as a rectangle and then yank it beside the first line of the
list.

 You can also copy rectangles into and out of registers with C-x r r r and C-x
r i r. See Rectangle Registers.

 The command M-x string-rectangle is similar to C-x r o, but it inserts a
specified string instead of blanks.  You specify the string with the
minibuffer.  Since the length of the string specifies how many columns to
insert, the width of the region-rectangle does not matter for this command.
What does matter is the position of the left edge (which specifies the column
position for the insertion in each line) and the range of lines that the
rectangle occupies.  The previous contents of the text after the insertion
column are pushed rightward.

 There are two commands for making with blank rectangles: M-x clear-rectangle
to blank out existing text, and C-x r o (open-rectangle) to insert a blank
rectangle.  Clearing a rectangle is equivalent to deleting it and then
inserting a blank rectangle of the same size.


ΓòÉΓòÉΓòÉ 14. Registers ΓòÉΓòÉΓòÉ

 Emacs registers are places you can save text or positions for later use.  Text
and rectangles saved in registers can be copied into the buffer once or many
times; you can move point to a position saved in a register.

 Each register has a name which is a single character.  A register can store a
piece of text, a rectangle, a position, a window configuration or a file name,
but only one thing at any given time.  Whatever you store in a register remains
there until you store something else in that register.  To see what a register
r contains, use M-x view-register.

M-x view-register RET r
          Display a description of what register r contains.


ΓòÉΓòÉΓòÉ 14.1. Saving Positions in Registers ΓòÉΓòÉΓòÉ

 Saving a position records a spot in a buffer so that you can move back there
later.  Moving to a saved position reselects that buffer and moves point to
that spot.

C-x r SPC r
          Save position of point in register r (point-to-register).

C-x r j r
          Jump to the position saved in register r (jump-to-register).

 To save the current position of point in a register, choose a name r and type
C-x r SPC r.  The register r retains the position thus saved until you store
something else in that register.

 The command C-x r j r moves point to the position recorded in register r.  The
register is not affected; it continues to record the same position.  You can
jump to the same position using the same register any number of times.


ΓòÉΓòÉΓòÉ 14.2. Saving Text in Registers ΓòÉΓòÉΓòÉ

 When you want to insert a copy of the same piece of text several times, it may
be inconvenient to yank it from the kill ring, since each subsequent kill moves
that entry further down the ring.  An alternative is to store the text in a
register with C-x r s (copy-to-register) and then retrieve it with C-x r i
(insert-register).

C-x r s r
          Copy region into register r (copy-to-register).

C-x r i r
          Insert text from register r (insert-register).

 C-x r s r stores a copy of the text of the region into the register named r.
Given a numeric argument, C-x r s r deletes the text from the buffer as well.

 C-x r i r inserts in the buffer the text from register r.  Normally it leaves
point before the text and places the mark after, but with a numeric argument
(C-u) it puts point after the text and the mark before.


ΓòÉΓòÉΓòÉ 14.3. Saving Rectangles in Registers ΓòÉΓòÉΓòÉ

 A register can contain a rectangle instead of linear text.  The rectangle is
represented as a list of strings.  See Rectangles, for basic information on how
to specify a rectangle in the buffer.

C-x r r r
          Copy the region-rectangle into register r (copy-region-to-rectangle).
          With numeric argument, delete it as well.

C-x r i r
          Insert the rectangle stored in register r (if it contains a
          rectangle) (insert-register).

 The C-x r i r command inserts a text string if the register contains one, and
inserts a rectangle if the register contains one.


ΓòÉΓòÉΓòÉ 14.4. Saving Window Configurations in Registers ΓòÉΓòÉΓòÉ

 You can save the window configuration of the selected frame in a register, or
even the configuration of all frames, and restore the configuration later.

C-x r w r
          Save the state of the selected frame's windows in register r
          (window-configuration-to-register).

C-x r f r
          Save the state of all windows in all frames in register r
          (frame-configuration-to-register).

 Use C-x r j r to restore a window or frame configuration. This is the same
command used to restore a cursor position.


ΓòÉΓòÉΓòÉ 14.5. Keeping File Names in Registers ΓòÉΓòÉΓòÉ

 If you visit certain file names frequently, you can visit them more
conveniently if you put their names in registers.  Here's the Lisp code used to
put a file name in a register:

(set-register ?r '(file . name))

For example,

(set-register ?z '(file . "/gd/gnu/emacs/19.0/src/ChangeLog"))

puts the file name shown in register `z'.

 To visit the file whose name is in register r, type C-x r j r.  (This is the
same command used to jump to a position or restore a frame configuration.)


ΓòÉΓòÉΓòÉ 15. Controlling the Display ΓòÉΓòÉΓòÉ

 Since only part of a large buffer fits in the window, Emacs tries to show the
part that is likely to be interesting.  The display control commands allow you
to specify which part of the text you want to see.

C-l
          Clear screen and redisplay, scrolling the selected window to center
          point vertically within it (recenter).

C-v
          Scroll forward (a windowful or a specified number of lines)
          (scroll-up).

NEXT
          Likewise, scroll forward.

M-v
          Scroll backward (scroll-down).

PRIOR
          Likewise, scroll backward.

arg C-l
          Scroll so point is on line arg (recenter).

C-x <
          Scroll text in current window to the left (scroll-left).

C-x >
          Scroll to the right (scroll-right).

C-x $
          Make deeply indented lines invisible (set-selective-display).

 The names of all scroll commands are based on the direction that the text
moves in the window.  Thus, the command to scrolling forward is called
scroll-up, since the text moves up.


ΓòÉΓòÉΓòÉ 15.1. Scrolling ΓòÉΓòÉΓòÉ

 If a buffer contains text that is too large to fit entirely within a window
that is displaying the buffer, Emacs shows a contiguous portion of the text.
The portion shown always contains point.

 Scrolling means moving text up or down in the window so that different parts
of the text are visible.  Scrolling forward means that text moves up, and new
text appears at the bottom.  Scrolling backward moves text down and new text
appears at the top.

 Scrolling happens automatically if you move point past the bottom or top of
the window.  You can also explicitly request scrolling with the commands in
this section.

C-l
          Clear screen and redisplay, scrolling the selected window to center
          point vertically within it (recenter).

C-v
          Scroll forward (a windowful or a specified number of lines)
          (scroll-up).

NEXT
          Likewise, scroll forward.

M-v
          Scroll backward (scroll-down).

PRIOR
          Likewise, scroll backward.

arg C-l
          Scroll so point is on line arg (recenter).

C-M-l
          Scroll heuristically to bring useful information onto the screen
          (reposition-window).

 The most basic scrolling command is C-l (recenter) with no argument.  It
clears the entire screen and redisplays all windows. In addition, it scrolls
the selected window so that point is halfway down from the top of the window.

 The scrolling commands C-v and M-v let you move all the text in the window up
or down a few lines.  C-v (scroll-up) with an argument shows you that many more
lines at the bottom of the window, moving the text and point up together as C-l
might.  C-v with a negative argument shows you more lines at the top of the
window. M-v (scroll-down) is like C-v, but moves in the opposite direction.
The function keys NEXT and PRIOR are equivalent to C-v and M-v.

 To read the buffer a windowful at a time, use C-v with no argument. It takes
the last two lines at the bottom of the window and puts them at the top,
followed by nearly a whole windowful of lines not previously visible.  If point
was in the text scrolled off the top, it moves to the new top of the window.
M-v with no argument moves backward with overlap similarly.  The number of
lines of overlap across a C-v or M-v is controlled by the variable
next-screen-context-lines; by default, it is two.

 Another way to do scrolling is with C-l with a numeric argument. C-l does not
clear the screen when given an argument; it only scrolls the selected window.
With a positive argument n, it repositions text to put point n lines down from
the top.  An argument of zero puts point on the very top line.  Point does not
move with respect to the text; rather, the text and point move rigidly on the
screen.  C-l with a negative argument puts point that many lines from the
bottom of the window. For example, C-u - 1 C-l puts point on the bottom line,
and C-u - 5 C-l puts it five lines from the bottom.  Just C-u as argument, as
in C-u C-l, scrolls point to the center of the screen.

 The C-M-l command (reposition-window) scrolls the current window heuristically
in a way designed to get useful information onto the screen.  For example, in a
Lisp file, this command tries to get the entire current defun onto the screen
if possible.

 Scrolling happens automatically if point has moved out of the visible portion
of the text when it is time to display.  Usually the scrolling is done so as to
put point vertically centered within the window.  However, if the variable
scroll-step has a nonzero value, an attempt is made to scroll the buffer by
that many lines; if that is enough to bring point back into visibility, that is
what is done.


ΓòÉΓòÉΓòÉ 15.2. Horizontal Scrolling ΓòÉΓòÉΓòÉ

C-x <
          Scroll text in current window to the left (scroll-left).

C-x >
          Scroll to the right (scroll-right).

 The text in a window can also be scrolled horizontally.  This means that each
line of text is shifted sideways in the window, and one or more characters at
the beginning of each line are not displayed at all.  When a window has been
scrolled horizontally in this way, text lines are truncated rather than
continued (see Continuation Lines), with a `$' appearing in the first column
when there is text truncated to the left, and in the last column when there is
text truncated to the right.

 The command C-x < (scroll-left) scrolls the selected window to the left by n
columns with argument n.  This moves part of the beginning of each line off the
left edge of the window. With no argument, it scrolls by almost the full width
of the window (two columns less, to be precise).

 C-x > (scroll-right) scrolls similarly to the right.  The window cannot be
scrolled any farther to the right once it is displaying normally (with each
line starting at the window's left margin); attempting to do so has no effect.
This means that you don't have to calculate the argument precisely for C-x >;
any sufficiently large argument will restore normally display.


ΓòÉΓòÉΓòÉ 15.3. Selective Display ΓòÉΓòÉΓòÉ

 Emacs has the ability to hide lines indented more than a certain number of
columns (you specify how many columns).  You can use this to get an overview of
a part of a program.

 To hide lines, type C-x $ (set-selective-display) with a numeric argument n.
Then lines with at least n columns of indentation disappear from the screen.
The only indication of their presence is that three dots (`...') appear at the
end of each visible line that is followed by one or more invisible ones.

 The commands C-n and C-p move across the invisible lines as if they were not
there.

 The invisible lines are still present in the buffer, and most editing commands
see them as usual, so you may find point in the middle of invisible text.  When
this happens, the cursor appears at the end of the previous line, after the
three dots.  If point is at the end of the visible line, before the newline
that ends it, the cursor appears before the three dots.

 To make everything visible again, type C-x $ with no argument.


ΓòÉΓòÉΓòÉ 15.4. European Character Set Display ΓòÉΓòÉΓòÉ

 Emacs can display accented characters, assuming the font in use supports them.
The M-x standard-display-european command toggles European character display.
When enabled, Emacs displays characters according to the ISO 8859 Latin-1
encoding for European languages; when disabled, Emacs uses octal notation for
all characters not specified by the ordinary ASCII standard.  Load the library
iso-syntax to specify the correct syntactic properties for the character codes
128 and above.

 With a prefix argument, M-x standard-display-european enables European
character display if and only if the argument is positive.

 If your terminal can send character codes 128 and up to represent ISO Latin-1
characters, execute the following expression to enable Emacs to understand
them:

(set-input-mode (car (current-input-mode))
                (nth 1 (current-input-mode))
                0)

Otherwise, you can load the library iso-insert to turn the key C-x 8 into a
``compose character'' prefix for insertion of the extra ISO Latin-1 printing
characters.


ΓòÉΓòÉΓòÉ 15.5. Optional Display Features ΓòÉΓòÉΓòÉ

 To add the current line number of point to the mode line, enable Line Number
mode with the command M-x line-number-mode.  The line number appears before
pos, with the letter `L' to indicate what it is.  See Minor Modes, for more
information about minor modes and about how to use this command.

 If the buffer is very large (larger than the value of
line-number-display-limit), then the line number doesn't appear. Emacs doesn't
compute the line number when the buffer is large, because that would be too
slow.

 Emacs can optionally display the time and system load in all mode lines.  To
enable this feature, type M-x display-time.  The information added to the mode
line usually appears after the buffer name, before the mode names and their
parentheses.  It looks like this:

hh:mmpm l.ll [d]

Here hh and mm are the hour and minute, followed always by `am' or `pm'.  l.ll
is the average number of running processes in the whole system recently.  d is
an approximate index of the ratio of disk activity to cpu activity for all
users.  (Some fields may be missing if your operating system cannot support
them.)

 The word `Mail' appears after the load level if there is mail for you that you
have not read yet.

 Customization note: the variable mode-line-inverse-video controls whether the
mode line is displayed in inverse video (assuming the terminal supports it);
nil means no inverse video.  The default is t. See Display Vars.


ΓòÉΓòÉΓòÉ 15.6. Variables Controlling Display ΓòÉΓòÉΓòÉ

 This section contains information for customization only.  Beginning users
should skip it.

 The variable mode-line-inverse-video controls whether the mode line is
displayed in inverse video (assuming the terminal supports it); nil means don't
do so.  See Mode Line.

 If the variable inverse-video is non-nil, Emacs attempts to invert all the
lines of the display from what they normally are.

 If the variable visible-bell is non-nil, Emacs attempts to make the whole
screen blink when it would normally make an audible bell sound.  This variable
has no effect if your terminal does not have a way to make the screen blink.

 When you reenter Emacs after suspending, Emacs normally clears the screen and
redraws the entire display.  On some terminals with more than one page of
memory, it is possible to arrange the termcap entry so that the `ti' and `te'
strings (output to the terminal when Emacs is entered and exited, respectively)
switch between pages of memory so as to use one page for Emacs and another page
for other output.  Then you might want to set the variable no-redraw-on-reenter
non-nil; this tells Emacs to assume, when resumed, that the screen page it is
using still contains what Emacs last wrote there.

 The variable echo-keystrokes controls the echoing of multi-character keys; its
value is the number of seconds of pause required to cause echoing to start, or
zero meaning don't echo at all.  See Echo Area.

 If the variable ctl-arrow is nil, control characters in the buffer are
displayed with octal escape sequences, all except newline and tab.  Altering
the value of ctl-arrow makes it local to the current buffer; until that time,
the default value is in effect.  The default is initially t. See Display
Tables.

 Normally, a tab character in the buffer is displayed as whitespace which
extends to the next display tab stop position, and display tab stops come at
intervals equal to eight spaces.  The number of spaces per tab is controlled by
the variable tab-width, which is made local by changing it, just like
ctl-arrow.  Note that how the tab character in the buffer is displayed has
nothing to do with the definition of TAB as a command.  The variable tab-width
must have an integer value between 1 and 1000, inclusive.

 If you set the variable selective-display-ellipses to nil, the three dots do
not appear at the end of a line that precedes invisible lines.  Then there is
no visible indication of the invisible lines. This variable too becomes local
automatically when set.

 If the variable truncate-lines is non-nil, then each line of text gets just
one screen line for display; if the text line is too long, display shows only
the part that fits.  If truncate-lines is nil, then long text lines display as
more than one screen line, enough to show the whole text of the line. See
Continuation Lines.  Altering the value of truncate-lines makes it local to the
current buffer; until that time, the default value is in effect.  The default
is initially nil.

 If the variable truncate-partial-width-windows is non-nil, it forces
truncation rather than continuation in any window less than the full width of
the screen or frame, regardless of the value of truncate-lines.  For
information about side-by-side windows, see Split Window.  See also Display.

 The variable baud-rate holds the the output speed of the terminal, as far as
Emacs knows.  Setting this variable does not change the speed of actual data
transmission, but the value is used for calculations such as padding.  It also
affects decisions about whether to scroll part of the screen or redraw it
instead---even when using a window system, (We designed it this way, despite
the fact that a window system has no true ``output speed'', to give you a way
to tune these decisions.)


ΓòÉΓòÉΓòÉ 16. Searching and Replacement ΓòÉΓòÉΓòÉ

 Like other editors, Emacs has commands for searching for occurrences of a
string.  The principal search command is unusual in that it is incremental; it
begins to search before you have finished typing the search string.  There are
also nonincremental search commands more like those of other editors.

 Besides the usual replace-string command that finds all occurrences of one
string and replaces them with another, Emacs has a fancy replacement command
called query-replace which asks interactively which occurrences to replace.


ΓòÉΓòÉΓòÉ 16.1. Incremental Search ΓòÉΓòÉΓòÉ

 An incremental search begins searching as soon as you type the first character
of the search string.  As you type in the search string, Emacs shows you where
the string (as you have typed it so far) would be found.  When you have typed
enough characters to identify the place you want, you can stop.  Depending on
what you plan to do next, you may or may not need to terminate the search
explicitly with RET.

C-s
          Incremental search forward (isearch-forward).

C-r
          Incremental search backward (isearch-backward).

 C-s starts an incremental search.  C-s reads characters from the keyboard and
positions the cursor at the first occurrence of the characters that you have
typed.  If you type C-s and then F, the cursor moves right after the first `F'.
Type an O, and see the cursor move to after the first `FO'.  After another O,
the cursor is after the first `FOO' after the place where you started the
search.  Meanwhile, the search string `FOO' has been echoed in the echo area.

 If you make a mistake in typing the search string, you can cancel characters
with DEL.  Each DEL cancels the last character of search string.  This does not
happen until Emacs is ready to read another input character; first it must
either find, or fail to find, the character you want to erase.  If you do not
want to wait for this to happen, use C-g as described below.

 When you are satisfied with the place you have reached, you can type RET,
which stops searching, leaving the cursor where the search brought it.  Also,
any command not specially meaningful in searches stops the searching and is
then executed.  Thus, typing C-a would exit the search and then move to the
beginning of the line.  RET is necessary only if the next command you want to
type is a printing character, DEL, RET, or another control character that is
special within searches (C-q, C-w, C-r, C-s, C-y, M-r, or M-s).

 Sometimes you search for `FOO' and find it, but not the one you expected to
find.  There was a second `FOO' that you forgot about, before the one you were
looking for.  In this event, type another C-s to move to the next occurrence of
the search string.  This can be done any number of times.  If you overshoot,
you can cancel some C-s characters with DEL.

 After you exit a search, you can search for the same string again by typing
just C-s C-s: the first C-s is the key that invokes incremental search, and the
second C-s means ``search again''.

 To reuse earlier search strings, use the search ring.  The commands M-p and
M-n move through the ring to pick a search string to reuse.  These commands
leave the selected search ring element in the minibuffer, where you can edit
it.  Type C-s or C-r to terminate editing the string and search for it.

 If your string is not found at all, the echo area says `Failing I-Search'.
The cursor is after the place where Emacs found as much of your string as it
could.  Thus, if you search for `FOOT', and there is no `FOOT', you might see
the cursor after the `FOO' in `FOOL'. At this point there are several things
you can do.  If your string was mistyped, you can rub some of it out and
correct it.  If you like the place you have found, you can type RET or some
other Emacs command to ``accept what the search offered''.  Or you can type
C-g, which removes from the search string the characters that could not be
found (the `T' in `FOOT'), leaving those that were found (the `FOO' in `FOOT').
A second C-g at that point cancels the search entirely, returning point to
where it was when the search started.

 An upper-case letter in the search string makes the search case-sensitive.  If
you delete the upper-case character from the search string, it ceases to have
this effect.  See Search Case.

 If a search is failing and you ask to repeat it by typing another C-s, it
starts again from the beginning of the buffer.  Repeating a failing reverse
search with C-r starts again from the end.  This is called wrapping around.
`Wrapped' appears in the search prompt once this has happened.

 The C-g ``quit'' character does special things during searches; just what it
does depends on the status of the search.  If the search has found what you
specified and is waiting for input, C-g cancels the entire search.  The cursor
moves back to where you started the search.  If C-g is typed when there are
characters in the search string that have not been found---because Emacs is
still searching for them, or because it has failed to find them---then the
search string characters which have not been found are discarded from the
search string.  With them gone, the search is now successful and waiting for
more input, so a second C-g will cancel the entire search.

 To search for a newline, type LFD (also known as C-j).  To search for another
control character such as control-S or carriage return, you must quote it by
typing C-q first.  This function of C-q is analogous to its meaning as an Emacs
command: it causes the following character to be treated the way a graphic
character would normally be treated in the same context.  You can also specify
a character by its octal code: enter C-q followed by three octal digits.

 You can change to searching backwards with C-r.  If a search fails because the
place you started was too late in the file, you should do this. Repeated C-r
keeps looking for more occurrences backwards.  A C-s starts going forwards
again.  C-r in a search can be cancelled with DEL.

 If you know initially that you want to search backwards, you can use C-r
instead of C-s to start the search, because C-r is also a key running a command
(isearch-backward) to search backward.

 The characters C-y and C-w can be used in incremental search to grab text from
the buffer into the search string.  This makes it convenient to search for
another occurrence of text at point.  C-w copies the word after point as part
of the search string, advancing point over that word.  Another C-s to repeat
the search will then search for a string including that word.  C-y is similar
to C-w but copies all the rest of the current line into the search string.

 To customize the special characters that incremental search understands, alter
their bindings in the keymap isearch-mode-map.


ΓòÉΓòÉΓòÉ 16.1.1. Slow Terminal Incremental Search ΓòÉΓòÉΓòÉ

 Incremental search on a slow terminal uses a modified style of display that is
designed to take less time.  Instead of redisplaying the buffer at each place
the search gets to, it creates a new single-line window and uses that to
display the line that the search has found.  The single-line window comes into
play as soon as point gets outside of the text that is already on the screen.

 When you terminate the search, the single-line window is removed. Then Emacs
redisplays the window in which the search was done, to show its new position of
point.

 The slow terminal style of display is used when the terminal baud rate is less
than or equal to the value of the variable search-slow-speed, initially 1200.

 The number of lines to use in slow terminal search display is controlled by
the variable search-slow-window-lines.  1 is its normal value.


ΓòÉΓòÉΓòÉ 16.2. Nonincremental Search ΓòÉΓòÉΓòÉ

 Emacs also has conventional nonincremental search commands, which require you
to type the entire search string before searching begins.

C-s RET string RET
          Search for string.

C-r RET string RET
          Search backward for string.

 To do a nonincremental search, first type C-s RET.  This enters the minibuffer
to read the search string; terminate the string with RET, and then the search
takes place.  If the string is not found, the search command gets an error.

 The way C-s RET works is that the C-s invokes incremental search, which is
specially programmed to invoke nonincremental search if the argument you give
it is empty.  (Such an empty argument would otherwise be useless.)  C-r RET
also works this way.

 However, nonincremental searches performed using C-s RET do not call
search-forward right away.  The first thing done is to see if the next
character is C-w, which requests a word search. See Word Search.

 Forward and backward nonincremental searches are implemented by the commands
search-forward and search-backward.  These commands may be bound to keys in the
usual manner.  The feature that you can get to them via the incremental search
commands exists for historical reasons, and to avoid the need to find suitable
key sequences for them.


ΓòÉΓòÉΓòÉ 16.3. Word Search ΓòÉΓòÉΓòÉ

 Word search searches for a sequence of words without regard to how the words
are separated.  More precisely, you type a string of many words, using single
spaces to separate them, and the string can be found even if there are multiple
spaces, newlines or other punctuation between the words.

 Word search is useful for editing a printed document made with a text
formatter.  If you edit while looking at the printed, formatted version, you
can't tell where the line breaks are in the source file.  With word search, you
can search without having to know them.

C-s RET C-w words RET
          Search for words, ignoring details of punctuation.

C-r RET C-w words RET
          Search backward for words, ignoring details of punctuation.

 Word search is a special case of nonincremental search and is invoked with C-s
RET C-w.  This is followed by the search string, which must always be
terminated with RET.  Being nonincremental, this search does not start until
the argument is terminated.  It works by constructing a regular expression and
searching for that; see Regexp Search.

 Use C-r RET C-w to do backward word search.

 Forward and backward word searches are implemented by the commands
word-search-forward and word-search-backward.  These commands may be bound to
keys in the usual manner.  The feature that you can get to them via the
incremental search commands exists for historical reasons, and to avoid the
need to find suitable key sequences for them.


ΓòÉΓòÉΓòÉ 16.4. Regular Expression Search ΓòÉΓòÉΓòÉ

 A regular expression (regexp, for short) is a pattern that denotes a class of
alternative strings to match, possibly infinitely many.  In GNU Emacs, you can
search for the next match for a regexp either incrementally or not.

 Incremental search for a regexp is done by typing C-M-s
(isearch-forward-regexp).  This command reads a search string incrementally
just like C-s, but it treats the search string as a regexp rather than looking
for an exact match against the text in the buffer.  Each time you add text to
the search string, you make the regexp longer, and the new regexp is searched
for.  To search backward in the buffer, use C-M-r (isearch-backward-regexp).

 All of the control characters that do special things within an ordinary
incremental search have the same function in incremental regexp search.  Typing
C-s or C-r immediately after starting the search retrieves the last incremental
search regexp used; that is to say, incremental regexp and non-regexp searches
have independent defaults.  They also have separate search rings that you can
access with M-p and M-n.

 If you type SPC in incremental regexp search, it matches any sequence of
whitespace characters, including newlines.  If you want to match just a space,
type C-q SPC.

 Note that adding characters to the regexp in an incremental regexp search can
make the cursor move back and start again.  For example, if you have searched
for `foo' and you add `\|bar', the cursor backs up in case the first `bar'
precedes the first `foo'.

 Nonincremental search for a regexp is done by the functions re-search-forward
and re-search-backward.  You can invoke these with M-x, or bind them to keys,
or invoke them by way of incremental regexp search with C-M-s RET and C-M-r
RET.


ΓòÉΓòÉΓòÉ 16.5. Syntax of Regular Expressions ΓòÉΓòÉΓòÉ

 Regular expressions have a syntax in which a few characters are special
constructs and the rest are ordinary.  An ordinary character is a simple
regular expression which matches that same character and nothing else.  The
special characters are `$', `^', `.', `*', `+', `?', `[', `]' and `\'.  Any
other character appearing in a regular expression is ordinary, unless a `\'
precedes it.

 For example, `f' is not a special character, so it is ordinary, and therefore
`f' is a regular expression that matches the string `f' and no other string.
(It does not match the string `ff'.)  Likewise, `o' is a regular expression
that matches only `o'.  (When case distinctions are being ignored, these
regexps also match `F' and `O', but we consider this a generalization of ``the
same string'', rather than an exception.)

 Any two regular expressions a and b can be concatenated.  The result is a
regular expression which matches a string if a matches some amount of the
beginning of that string and b matches the rest of the string.

 As a simple example, we can concatenate the regular expressions `f' and `o' to
get the regular expression `fo', which matches only the string `fo'.  Still
trivial.  To do something nontrivial, you need to use one of the special
characters.  Here is a list of them.

. (Period)
          is a special character that matches any single character except a
          newline. Using concatenation, we can make regular expressions like
          `a.b' which matches any three-character string which begins with `a'
          and ends with `b'.

*
          is not a construct by itself; it is a postfix operator, which means
          to match the preceding regular expression repetitively as many times
          as possible.  Thus, `o*' matches any number of `o's (including no
          `o's).

          `*' always applies to the smallest possible preceding expression.
          Thus, `fo*' has a repeating `o', not a repeating `fo'.  It matches
          `f', `fo', `foo', and so on.

          The matcher processes a `*' construct by matching, immediately, as
          many repetitions as can be found.  Then it continues with the rest of
          the pattern.  If that fails, backtracking occurs, discarding some of
          the matches of the `*'-modified construct in case that makes it
          possible to match the rest of the pattern.  For example, matching
          `ca*ar' against the string `caaar', the `a*' first tries to match all
          three `a's; but the rest of the pattern is `ar' and there is only `r'
          left to match, so this try fails. The next alternative is for `a*' to
          match only two `a's. With this choice, the rest of the regexp matches
          successfully.

+
          is a postfix character, similar to `*' except that it must match the
          preceding expression at least once.  So, for example, `ca+r' matches
          the strings `car' and `caaaar' but not the string `cr', whereas
          `ca*r' matches all three strings.

?
          is a postfix character, similar to `*' except that it can match the
          preceding expression either once or not at all.  For example, `ca?r'
          matches `car' or `cr'; nothing else.

[ ... ]
          is a character set, which begins with `[' and is terminated by a `]'.
          In the simplest case, the characters between the two brackets are
          what this set can match.

          Thus, `[ad]' matches either one `a' or one `d', and `[ad]*' matches
          any string composed of just `a's and `d's (including the empty
          string), from which it follows that `c[ad]*r' matches `cr', `car',
          `cdr', `caddaar', etc.

          You can also include character ranges a character set, by writing two
          characters with a `-' between them.  Thus, `[a-z]' matches any
          lower-case letter.  Ranges may be intermixed freely with individual
          characters, as in `[a-z$%.]', which matches any lower case letter or
          `$', `%' or period.

          Note that the usual special characters are not special any more
          inside a character set.  A completely different set of special
          characters exists inside character sets: `]', `-' and `^'.

          To include a `]' in a character set, you must make it the first
          character.  For example, `[]a]' matches `]' or `a'.  To include a
          `-', write `-' at the beginning or end of a range. To include `^',
          make it other than the first character in the set.

[^ ... ]
          `[^' begins a complemented character set, which matches any character
          except the ones specified.  Thus, `[^a-z0-9A-Z]' matches all
          characters except letters and digits.

          `^' is not special in a character set unless it is the first
          character.  The character following the `^' is treated as if it were
          first (`-' and `]' are not special there).

          A complemented character set can match a newline, unless newline is
          mentioned as one of the characters not to match.  This is in contrast
          to the handling of regexps in programs such as grep.

^
          is a special character that matches the empty string, but only at the
          beginning of a line in the text being matched.  Otherwise it fails to
          match anything.  Thus, `^foo' matches a `foo' which occurs at the
          beginning of a line.

$
          is similar to `^' but matches only at the end of a line.  Thus,
          `xx*$' matches a string of one `x' or more at the end of a line.

\
          has two functions: it quotes the special characters (including `\'),
          and it introduces additional special constructs.

          Because `\' quotes special characters, `\$' is a regular expression
          which matches only `$', and `\[' is a regular expression which
          matches only `[', etc.

Note: for historical compatibility, special characters are treated as ordinary
ones if they are in contexts where their special meanings make no sense.  For
example, `*foo' treats `*' as ordinary since there is no preceding expression
on which the `*' can act.  It is poor practice to depend on this behavior;
better to quote the special character anyway, regardless of where is appears.

For the most part, `\' followed by any character matches only that character.
However, there are several exceptions: two-character sequences starting with
`\' which have special meanings.  The second character in the sequence is
always an ordinary character on their own.  Here is a table of `\' constructs.

\|
          specifies an alternative.  Two regular expressions a and b with `\|'
          in between form an expression that matches anything that either a or
          b matches.

          Thus, `foo\|bar' matches either `foo' or `bar' but no other string.

          `\|' applies to the largest possible surrounding expressions.  Only a
          surrounding `\( ... \)' grouping can limit the scope of `\|'.

          Full backtracking capability exists to handle multiple uses of `\|'.

\( ... \)
          is a grouping construct that serves three purposes:

    1. To enclose a set of `\|' alternatives for other operations. Thus,
       `\(foo\|bar\)x' matches either `foox' or `barx'.

    2. To enclose a complicated expression for the postfix operators `*', `+'
       and `?' to operate on.  Thus, `ba\(na\)*' matches `bananana', etc., with
       any (zero or more) number of `na' strings.

    3. To mark a matched substring for future reference.

          This last application is not a consequence of the idea of a
          parenthetical grouping; it is a separate feature which is assigned as
          a second meaning to the same `\( ... \)' construct.  In practice
          there is no conflict between the two meanings.  Here is an
          explanation of this feature:

\d
          after the end of a `\( ... \)' construct, the matcher remembers the
          beginning and end of the text matched by that construct.  Then, later
          on in the regular expression, you can use `\' followed by the digit d
          to mean ``match the same text matched the dth time by the `\( ... \)'
          construct.''

          The strings matching the first nine `\( ... \)' constructs appearing
          in a regular expression are assigned numbers 1 through 9 in order
          that the open-parentheses appear in the regular expression. `\1'
          through `\9' refer to the text previously matched by the
          corresponding `\( ... \)' construct.

          For example, `\(.*\)\1' matches any newline-free string that is
          composed of two identical halves.  The `\(.*\)' matches the first
          half, which may be anything, but the `\1' that follows must match the
          same exact text.

\`
          matches the empty string, provided it is at the beginning of the
          buffer.

\'
          matches the empty string, provided it is at the end of the buffer.

\b
          matches the empty string, provided it is at the beginning or end of a
          word.  Thus, `\bfoo\b' matches any occurrence of `foo' as a separate
          word.  `\bballs?\b' matches `ball' or `balls' as a separate word.

\B
          matches the empty string, provided it is not at the beginning or end
          of a word.

\<
          matches the empty string, provided it is at the beginning of a word.

\>
          matches the empty string, provided it is at the end of a word.

\w
          matches any word-constituent character.  The syntax table determines
          which characters these are.

\W
          matches any character that is not a word-constituent.

\sc
          matches any character whose syntax is c.  Here c is a character which
          represents a syntax code: thus, `w' for word constituent, `(' for
          open-parenthesis, etc.  Represent a character of whitespace (which
          can be a newline) by either `-' or a space character.

\Sc
          matches any character whose syntax is not c.

 The constructs that pertain to words and syntax are controlled by the setting
of the syntax table (see Syntax).

 Here is a complicated regexp, used by Emacs to recognize the end of a sentence
together with any whitespace that follows.  It is given in Lisp syntax to
enable you to distinguish the spaces from the tab characters.  In Lisp syntax,
the string constant begins and ends with a double-quote. `\"' stands for a
double-quote as part of the regexp, `\\' for a backslash as part of the regexp,
`\t' for a tab and `\n' for a newline.

"[.?!][]\"')]*\\($\\|\t\\|  \\)[ \t\n]*"

This contains four parts in succession: a character set matching period, `?',
or `!'; a character set matching close-brackets, quotes, or parentheses,
repeated any number of times; an alternative in backslash-parentheses that
matches end-of-line, a tab, or two spaces; and a character set matching
whitespace characters, repeated any number of times.

 To enter the same regexp interactively, you would type TAB to enter a tab, and
C-q C-j to enter a newline.  You would also type single slashes as themselves,
instead of doubling them for Lisp syntax.


ΓòÉΓòÉΓòÉ 16.6. Searching and Case ΓòÉΓòÉΓòÉ

 All sorts of searches in Emacs normally ignore the case of the text they are
searching through, if you specify the text in lower case. Thus, if you specify
searching for `foo', then `Foo' and `foo' are also considered a match.
Regexps, and in particular character sets, are included: `[ab]' would match `a'
or `A' or `b' or `B'.

 An upper-case letter in the search string makes the search case-sensitive.
Thus, searching for `Foo' does not find `foo' or `FOO'.  This applies to
regular expression search also.  If you delete the upper-case character from
the search string, it ceases to have this effect.

 If you set the variable case-fold-search to nil, then all letters must match
exactly, including case.  This is a per-buffer variable; altering the variable
affects only the current buffer, but there is a default value which you can
change as well.  See Locals.


ΓòÉΓòÉΓòÉ 16.7. Replacement Commands ΓòÉΓòÉΓòÉ

 Global search-and-replace operations are not needed as often in Emacs as they
are in other editors (In some editors, search-and-replace operations are the
only convenient way to make a single change in the text.) , but they are
available.  In addition to the simple M-x replace-string command which is like
that found in most editors, there is a M-x query-replace command which asks
you, for each occurrence of the pattern, whether to replace it.

 The replace commands all replace one string (or regexp) with one replacement
string.  It is possible to perform several replacements in parallel using the
command expand-region-abbrevs. See Expanding Abbrevs.


ΓòÉΓòÉΓòÉ 16.7.1. Unconditional Replacement ΓòÉΓòÉΓòÉ

M-x replace-string RET string RET newstring RET
          Replace every occurrence of string with newstring.

M-x replace-regexp RET regexp RET newstring RET
          Replace every match for regexp with newstring.

 To replace every instance of `foo' after point with `bar', use the command M-x
replace-string with the two arguments `foo' and `bar'.  Replacement happens
only in the text after point, so if you want to cover the whole buffer you must
go to the beginning first.  All occurrences up to the end of the buffer are
replaced; to limit replacement to part of the buffer, narrow to that part of
the buffer before doing the replacement (see Narrowing).

 When replace-string exits, point is left at the last occurrence replaced.  The
position of point where the replace-string command was issued is remembered on
the mark ring; use C-u C-SPC to move back there.

 A numeric argument restricts replacement to matches that are surrounded by
word boundaries.


ΓòÉΓòÉΓòÉ 16.7.2. Regexp Replacement ΓòÉΓòÉΓòÉ

 The M-x replace-string command replaces exact matches for a single string.
The similar command M-x replace-regexp replaces any match for a specified
pattern.

 In replace-regexp, the newstring need not be constant: it can refer to all or
part of what is matched by the regexp. `\&' in newstring stands for the entire
text being replaced. `\d' in newstring, where d is a digit, stands for whatever
matched the dth parenthesized grouping in regexp. To include a `\' in the text
to replace with, you must give `\\'.  For example,

M-x replace-regexp RET c[ad]+r RET \&-safe RET

replaces (for example) `cadr' with `cadr-safe' and `cddr' with `cddr-safe'.

M-x replace-regexp RET \(c[ad]+r\)-safe RET \1 RET

performs the inverse transformation.


ΓòÉΓòÉΓòÉ 16.7.3. Replace Commands and Case ΓòÉΓòÉΓòÉ

 If the arguments to a replace command are in lower case, it preserves case
when it makes a replacement.  Thus, the command

M-x replace-string RET foo RET bar RET

replaces a lower case `foo' with a lower case `bar', `FOO' with `BAR', and
`Foo' with `Bar'.  If upper case letters are used in the second argument, they
remain upper case every time that argument is inserted.  If upper case letters
are used in the first argument, the second argument is always substituted
exactly as given, with no case conversion.  Likewise, if the variable
case-replace is set to nil, replacement is done without case conversion.  If
case-fold-search is set to nil, case is significant in matching occurrences of
`foo' to replace; this also inhibits case conversion of the replacement string.


ΓòÉΓòÉΓòÉ 16.7.4. Query Replace ΓòÉΓòÉΓòÉ

M-% string RET newstring RET
M-x query-replace RET string RET newstring RET
          Replace some occurrences of string with newstring.

M-x query-replace-regexp RET regexp RET newstring RET
          Replace some matches for regexp with newstring.

 If you want to change only some of the occurrences of `foo' to `bar', not all
of them, then you cannot use an ordinary replace-string.  Instead, use M-%
(query-replace). This command finds occurrences of `foo' one by one, displays
each occurrence and asks you whether to replace it.  A numeric argument to
query-replace tells it to consider only occurrences that are bounded by
word-delimiter characters.  This preserves case, just like replace-string,
provided case-replace is non-nil, as it normally is.

 Aside from querying, query-replace works just like replace-string, and
query-replace-regexp works just like replace-regexp.  The shortest way to type
this command name is M-x qu SPC SPC SPC RET.

 The things you can type when you are shown an occurrence of string or a match
for regexp are:

SPC
          to replace the occurrence with newstring.

DEL
          to skip to the next occurrence without replacing this one.

, (Comma)
          to replace this occurrence and display the result.  You are then
          asked for another input character, except that since the replacement
          has already been made, DEL and SPC are equivalent.  You could type
          C-r at this point (see below) to alter the replaced text.  You could
          also type C-x u to undo the replacement; this exits the
          query-replace, so if you want to do further replacement you must use
          C-x ESC RET to restart (see Repetition).

RET
ESC
          to exit without doing any more replacements.

. (Period)
          to replace this occurrence and then exit without searching for more
          occurrences.

!
          to replace all remaining occurrences without asking again.

^
          to go back to the position of the previous occurrence (or what used
          to be an occurrence), in case you changed it by mistake.  This works
          by popping the mark ring.  Only one ^ in a row is allowed, because
          only one previous replacement position is kept during query-replace.

C-r
          to enter a recursive editing level, in case the occurrence needs to
          be edited rather than just replaced with newstring.  When you are
          done, exit the recursive editing level with C-M-c to proceed to the
          next occurrence.  See Recursive Edit.

C-w
          to delete the occurrence, and then enter a recursive editing level as
          in C-r.  Use the recursive edit to insert text to replace the deleted
          occurrence of string.  When done, exit the recursive editing level
          with C-M-c to proceed to the next occurrence.

C-l
          to redisplay the screen.  Then you must type another character to
          specify what to do with this occurrence.

C-h
          to display a message summarizing these options.  Then you must type
          another character to specify what to do with this occurrence.

 Some other characters are aliases for the ones listed above: y, n and q are
equivalent to SPC, DEL and ESC.

 Aside from this, any other character exits the query-replace, and is then
reread as part of a key sequence.  Thus, if you type C-k, it exits the
query-replace and then kills to end of line.

 To restart a query-replace once it is exited, use C-x ESC, which repeats the
query-replace because it used the minibuffer to read its arguments.  See
Repetition.

 See also Transforming File Names, for Dired commands to rename, copy, or link
files by replacing regexp matches in file names.


ΓòÉΓòÉΓòÉ 16.8. Other Search-and-Loop Commands ΓòÉΓòÉΓòÉ

 Here are some other commands that find matches for a regular expression. They
all operate from point to the end of the buffer.

M-x occur RET regexp RET
          Print each line that follows point and contains a match for regexp.
          A numeric argument specifies the number of context lines to print
          before and after each matching line; the default is none.

          The buffer `*Occur*' containing the output serves as a menu for
          finding the occurrences in their original context.  Find an
          occurrence as listed in `*Occur*', position point there and type C-c
          C-c; this switches to the buffer that was searched and moves point to
          the original of the same occurrence.

M-x list-matching-lines
          Synonym for M-x occur.

M-x count-matches RET regexp RET
          Print the number of matches for regexp after point.

M-x flush-lines RET regexp RET
          Delete each line that follows point and does not contain a match for
          regexp.

M-x keep-lines RET regexp RET
          Delete each line that follows point and contains a match for regexp.


ΓòÉΓòÉΓòÉ 17. Commands for Fixing Typos ΓòÉΓòÉΓòÉ

 In this chapter we describe the commands that are especially useful for the
times when you catch a mistake in your text just after you have made it, or
change your mind while composing text on line.


ΓòÉΓòÉΓòÉ 17.1. Killing Your Mistakes ΓòÉΓòÉΓòÉ

DEL
          Delete last character (delete-backward-char).

M-DEL
          Kill last word (backward-kill-word).

C-x DEL
          Kill to beginning of sentence (backward-kill-sentence).

 The DEL character (delete-backward-char) is the most important correction
command.  When used among graphic (self-inserting) characters, it can be
thought of as canceling the last character typed.

 When your mistake is longer than a couple of characters, it might be more
convenient to use M-DEL or C-x DEL. M-DEL kills back to the start of the last
word, and C-x DEL kills back to the start of the last sentence.  C-x DEL is
particularly useful when you change your mind about the phrasing of the text
you are writing.  M-DEL and C-x DEL save the killed text for C-y and M-y to
retrieve.  See Yanking.

 M-DEL is often useful even when you have typed only a few characters wrong, if
you know you are confused in your typing and aren't sure exactly what you
typed.  At such a time, you cannot correct with DEL except by looking at the
screen to see what you did.  It requires less thought to kill the whole word
and start over again.


ΓòÉΓòÉΓòÉ 17.2. Transposing Text ΓòÉΓòÉΓòÉ

C-t
          Transpose two characters (transpose-chars).

M-t
          Transpose two words (transpose-words).

C-M-t
          Transpose two balanced expressions (transpose-sexps).

C-x C-t
          Transpose two lines (transpose-lines).

 The common error of transposing two characters can be fixed, when they are
adjacent, with the C-t command (transpose-chars).  Normally, C-t transposes the
two characters on either side of point.  When given at the end of a line,
rather than transposing the last character of the line with the newline, which
would be useless, C-t transposes the last two characters on the line.  So, if
you catch your transposition error right away, you can fix it with just a C-t.
If you don't catch it so fast, you must move the cursor back to between the two
transposed characters.  If you transposed a space with the last character of
the word before it, the word motion commands are a good way of getting there.
Otherwise, a reverse search (C-r) is often the best way. See Search.

 M-t (transpose-words) transposes the word before point with the word after
point.  It moves point forward over a word, dragging the word preceding or
containing point forward as well.  The punctuation characters between the words
do not move.  For example, `FOO, BAR' transposes into `BAR, FOO' rather than
`BAR FOO,'.

 C-M-t (transpose-sexps) is a similar command for transposing two expressions
(see Lists), and C-x C-t (transpose-lines) exchanges lines.  They work like M-t
except in determining the division of the text into syntactic units.

 A numeric argument to a transpose command serves as a repeat count: it tells
the transpose command to move the character (word, sexp, line) before or
containing point across several other characters (words, sexps, lines).  For
example, C-u 3 C-t moves the character before point forward across three other
characters.  It would change `f-!-oobar' into `oobf-!-ar'.  This is equivalent
to repeating C-t three times.  C-u - 4 M-t moves the word before point backward
across four words.  C-u - C-M-t would cancel the effect of plain C-M-t.

 A numeric argument of zero is assigned a special meaning (because otherwise a
command with a repeat count of zero would do nothing): to transpose the
character (word, sexp, line) ending after point with the one ending after the
mark.


ΓòÉΓòÉΓòÉ 17.3. Case Conversion ΓòÉΓòÉΓòÉ

M-- M-l
          Convert last word to lower case.  Note Meta-- is Meta-minus.

M-- M-u
          Convert last word to all upper case.

M-- M-c
          Convert last word to lower case with capital initial.

 A very common error is to type words in the wrong case.  Because of this, the
word case-conversion commands M-l, M-u and M-c have a special feature when used
with a negative argument: they do not move the cursor.  As soon as you see you
have mistyped the last word, you can simply case-convert it and go on typing.
See Case.


ΓòÉΓòÉΓòÉ 17.4. Checking and Correcting Spelling ΓòÉΓòÉΓòÉ

 This section describes the commands to check the spelling of a single word or
of a portion of a buffer.

M-$
          Check and correct spelling of word at point (ispell-word).

M-x ispell-buffer
          Check and correct spelling of each word in the buffer.

M-x ispell-region
          Check and correct spelling of each word in the region.

M-x ispell-string RET word RET
          Check spelling of word.

M-x reload-ispell
          Make the Ispell subprocess reread your private dictionary.

M-x kill-ispell
          Kill the Ispell subprocess.

 To check the spelling of the word around or next to point, and optionally
correct it as well, use the command M-$  (ispell-word).  If the word is not
correct, the command offers  you various alternatives for what to do about it.

  To check the entire current buffer, use M-x ispell-buffer.  Use  M-x
ispell-region to check just the current region.  Each time  these commands
encounter an incorrect word, they ask you what to do.

  Whenever one of these commands finds an incorrect word, it displays a  list
of alternatives, usually including several ``near-misses''---words  that are
close to the word being checked.  Here are the valid responses:

SPC
           Skip this word---continue to consider it incorrect, but don't change
          it  here.

r new RET
           Replace the word (just this time) with new.

digit
           Replace the word (just this time) with one of the displayed
          near-misses.  Each near-miss is listed with a digit; type that digit
          to  select it.

a
           Accept the incorrect word---treat it as correct, but only in this
          editing session.

i
           Insert this word in your private dictionary file so that Ispell will
          consider it correct it from now on, even in future sessions.

l regexp RET
           Look in the dictionary for words that match regexp.  These words
          become the new list of ``near-misses''; you can select one of them to
          replace with by typing a digit.

C-g
           Quit interactive spell checking.  You can restart it again afterward
          with C-u M-$.

  The first time you use any of the spell checking commands, it starts  an
Ispell subprocess.  The first thing the subprocess does is read your  private
dictionary, which is the file `~/ispell.words'.  Words that  you ``insert''
with the i command are added to that file, but not  right away---only at the
end of the interactive replacement procedure.  Use the M-x reload-ispell
command to reload your private  dictionary from `~/ispell.words' if you edit
the file outside of  Ispell.

  Once started, the Ispell subprocess continues to run (waiting for  something
to do), so that subsequent spell checking commands complete  more quickly.  If
you want to get rid of the Ispell process, use  M-x kill-ispell.  This is not
usually necessary, since the process  uses no time except when you do spelling
correction.


ΓòÉΓòÉΓòÉ 18. File Handling ΓòÉΓòÉΓòÉ

 The basic unit of stored data in Unix is the file.  To edit a file, you must
tell Emacs to examine the file and prepare a buffer containing a copy of the
file's text.  This is called visiting the file.  Editing commands apply
directly to text in the buffer; that is, to the copy inside Emacs.  Your
changes appear in the file itself only when you save the buffer back into the
file.

 In addition to visiting and saving files, Emacs can delete, copy, rename, and
append to files, keep multiple versions of them, and operate on file
directories.


ΓòÉΓòÉΓòÉ 18.1. File Names ΓòÉΓòÉΓòÉ

 Most Emacs commands that operate on a file require you to specify the file
name.  (Saving and reverting are exceptions; the buffer knows which file name
to use for them.)  You enter the file name using the minibuffer (see
Minibuffer).  Completion is available, to make it easier to specify long file
names.  See Completion.

 For most operations, there is a default file name which is used if you type
just RET to enter an empty argument.  Normally the default file name is the
name of the file visited in the current buffer; this makes it easy to operate
on that file with any of the Emacs file commands.

 Each buffer has a default directory, normally the same as the directory of the
file visited in that buffer.  When you enter a file name without a directory,
the default directory is used.  If you specify a directory in a relative
fashion, with a name that does not start with a slash, it is interpreted with
respect to the default directory.  The default directory is kept in the
variable default-directory, which has a separate value in every buffer.

 For example, if the default file name is `/u/rms/gnu/gnu.tasks' then the
default directory is `/u/rms/gnu/'.  If you type just `foo', which does not
specify a directory, it is short for `/u/rms/gnu/foo'. `../.login' would stand
for `/u/rms/.login'.  `new/foo' would stand for the file name
`/u/rms/gnu/new/foo'.

 The command M-x pwd prints the current buffer's default directory, and the
command M-x cd sets it (to a value read using the minibuffer).  A buffer's
default directory changes only when the cd command is used.  A file-visiting
buffer's default directory is initialized to the directory of the file that is
visited there.  If you create a buffer with C-x b, its default directory is
copied from that of the buffer that was current at the time.

 The default directory actually appears in the minibuffer when the minibuffer
becomes active to read a file name.  This serves two purposes: it shows you
what the default is, so that you can type a relative file name and know with
certainty what it will mean, and it allows you to edit the default to specify a
different directory. This insertion of the default directory is inhibited if
the variable insert-default-directory is set to nil.

 Note that it is legitimate to type an absolute file name after you enter the
minibuffer, ignoring the presence of the default directory name as part of the
text.  The final minibuffer contents may look invalid, but that is not so.  For
example, if the minibuffer starts out with `/usr/tmp/' and you add
`/x1/rms/foo', the double slash says to ignore the default directory and use
just the name that you typed.  See Minibuffer File.

 You can refer to files on other machines using a special file name syntax:

/host:filename
/user@host:filename

 When you do this, Emacs uses the FTP program to read and write files on the
specified host.  It logs in through FTP using your user name or the name user.
It may ask you for a password from time to time; this is used for logging in on
host.

 `$' in a file name is used to substitute environment variables.  For example,
if you have used the shell command `setenv FOO rms/hacks' to set up an
environment variable named `FOO', then you can use `/u/$FOO/test.c' or
`/u/${FOO}/test.c' as an abbreviation for `/u/rms/hacks/test.c'.  The
environment variable name consists of all the alphanumeric characters after the
`$'; alternatively, it may be enclosed in braces after the `$'.  Note that the
`setenv' command affects Emacs only if done before Emacs is started.

 To access a file with `$' in its name, type `$$'.  This pair is converted to a
single `$' at the same time as variable substitution is performed for single
`$'.  The Lisp function that performs the substitution is called
substitute-in-file-name.  The substitution is performed only on file names read
as such using the minibuffer.


ΓòÉΓòÉΓòÉ 18.2. Visiting Files ΓòÉΓòÉΓòÉ

C-x C-f
          Visit a file (find-file).

C-x C-r
          Visit a file for viewing, without allowing changes to it
          (find-file-read-only).

C-x C-v
          Visit a different file instead of the one visited last
          (find-alternate-file).

C-x 4 C-f
          Visit a file, in another window (find-file-other-window).  Don't
          change the selected window.

C-x 5 C-f
          Visit a file, in a new frame (find-file-other-frame).  Don't change
          the selected frame.

 Visiting a file means copying its contents into an Emacs buffer so you can
edit them.  Emacs makes a new buffer for each file that you visit.  We say that
this buffer is visiting the file that it was created to hold.  Emacs constructs
the buffer name from the file name by throwing away the directory, keeping just
the name proper.  For example, a file named `/usr/rms/emacs.tex' would get a
buffer named `emacs.tex'.  If there is already a buffer with that name, a
unique name is constructed by appending `<2>', `<3>', or so on, using the
lowest number that makes a name that is not already in use.

 Each window's mode line shows the name of the buffer that is being displayed
in that window, so you can always tell what buffer you are editing.

 The changes you make with Emacs are made in the Emacs buffer.  They do not
take effect in the file that you visited, or any place permanent, until you
save the buffer.  Saving the buffer means that Emacs writes the current
contents of the buffer into its visited file.  See Saving.

 If a buffer contains changes that have not been saved, we say the buffer is
modified.  This is important because it implies that some changes will be lost
if the buffer is not saved.  The mode line displays two stars near the left
margin to indicate that the buffer is modified.

 To visit a file, use the command C-x C-f (find-file).  Follow the command with
the name of the file you wish to visit, terminated by a RET.

 The file name is read using the minibuffer (see Minibuffer), with defaulting
and completion in the standard manner (see File Names). While in the
minibuffer, you can abort C-x C-f by typing C-g.

 Your confirmation that C-x C-f has completed successfully is the appearance of
new text on the screen and a new buffer name in the mode line.  If the
specified file does not exist and could not be created, or cannot be read, then
you get an error, with an error message displayed in the echo area.

 If you visit a file that is already in Emacs, C-x C-f does not make another
copy.  It selects the existing buffer containing that file. However, before
doing so, it checks that the file itself has not changed since you visited or
saved it last.  If the file has changed, a warning message is printed.  See
Simultaneous Editing.

 What if you want to create a new file?  Just visit it.  Emacs prints `(New
File)' in the echo area, but in other respects behaves as if you had visited an
existing empty file.  If you make any changes and save them, the file is
created.

 If the file you specify is actually a directory, Dired is called on that
directory (see Dired).  This can be inhibited by setting the variable
find-file-run-dired to nil; then it is an error to try to visit a directory.

 If you visit a file that the operating system won't let you modify, Emacs
makes the buffer read-only, so that you won't go ahead and make changes that
you'll have trouble saving afterward.  You can make the buffer writable with
C-x C-q (toggle-read-only). See Misc Buffer.

 Occasionally you might want to visit a file as read-only in order to protect
yourself from entering changes accidentally; do so by visiting the file with
the command C-x C-r (find-file-read-only).

 If you visit a nonexistent file unintentionally (because you typed the wrong
file name), use the C-x C-v command (find-alternate-file) to visit the file you
really wanted. C-x C-v is similar to C-x C-f, but it kills the current buffer
(after first offering to save it if it is modified).  When it reads the file
name to visit, it inserts the entire default file name in the buffer, with
point just after the directory part; this is convenient if you made a slight
error in typing the name.

 C-x 4 f (find-file-other-window) is like C-x C-f except that the buffer
containing the specified file is selected in another window.  The window that
was selected before C-x 4 f continues to show the same buffer it was already
showing.  If this command is used when only one window is being displayed, that
window is split in two, with one window showing the same buffer as before, and
the other one showing the newly requested file.  See Windows.

 C-x 5 f (find-file-other-frame) is similar, but opens a new frame.  This
feature is available only when you are using a window system.  See Frames.

 Two special hook variables allow extensions to modify the operation of
visiting files.  Visiting a file that does not exist runs the functions in the
list find-file-not-found-hooks; this variable holds a list of functions, and
the functions are called one by one until one of them returns non-nil.  Any
visiting of a file, whether extant or not, expects find-file-hooks to contain a
list of functions and calls them all, one by one.  In both cases the functions
receive no arguments.  Of these two variables, find-file-not-found-hooks takes
effect first.  These variables are not normal hooks, and their names end in
`-hooks' rather than `-hook' to indicate that fact.

 There are several ways to specify automatically the major mode for editing the
file (see Choosing Modes), and to specify local variables defined for that file
(see File Variables).


ΓòÉΓòÉΓòÉ 18.3. Saving Files ΓòÉΓòÉΓòÉ

 Saving a buffer in Emacs means writing its contents back into the file that
was visited in the buffer.

C-x C-s
          Save the current buffer in its visited file (save-buffer).

C-x s
          Save any or all buffers in their visited files (save-some-buffers).

M-~
          Forget that the current buffer has been changed (not-modified).

C-x C-w
          Save the current buffer in a specified file (write-file).

M-x set-visited-file-name
          Change file the name under which the current buffer will be saved.

 When you wish to save the file and make your changes permanent, type C-x C-s
(save-buffer).  After saving is finished, C-x C-s prints a message such as

Wrote /u/rms/gnu/gnu.tasks

If the selected buffer is not modified (no changes have been made in it since
the buffer was created or last saved), saving is not really done, because it
would have no effect.  Instead, C-x C-s prints a message in the echo area
saying

(No changes need to be written)

 The command C-x s (save-some-buffers) offers to save any or all modified
buffers.  It asks you what to do with each buffer.  The options are analogous
to those of query-replace:

y
          Save this buffer and ask about the rest of the buffers.

n
          Don't save this buffer, but ask about the rest of the buffers.

!
          Save this buffer and all the rest with no more questions.

ESC
          Terminate save-some-buffers without any more saving.

.
          Save this buffer, then exit save-some-buffers without even asking
          about other buffers.

C-r
          View the buffer that you are currently being asked about.  When you
          exit View mode, you get back to save-some-buffers, which asks the
          question again.

C-h
          Display a help message about these options.

 C-x C-c, the key sequence to exit Emacs, invokes save-some-buffers and
therefore asks the same questions.

 If you have changed a buffer and do not want the changes to be saved, you
should take some action to prevent it.  Otherwise, each time you use C-x s or
C-x C-c, you are liable to save it by mistake.  One thing you can do is type
M-~ (not-modified), which clears out the indication that the buffer is
modified.  If you do this, none of the save commands will believe that the
buffer needs to be saved. (`~' is often used as a mathematical symbol for
`not'; thus M-~ is `not', metafied.)  You could also use set-visited-file-name
(see below) to mark the buffer as visiting a different file name, one which is
not in use for anything important. Alternatively, you can cancel all the
changes made since the file was visited or saved, by reading the text from the
file again.  This is called reverting.  See Reverting.  You could also undo all
the changes by repeating the undo command C-x u until you have undone all the
changes; but reverting is easier.

 M-x set-visited-file-name alters the name of the file that the current buffer
is visiting.  It reads the new file name using the minibuffer.  Then it
specifies the visited file name and changes the buffer name correspondingly (as
long as the new name is not in use). set-visited-file-name does not save the
buffer in the newly visited file; it just alters the records inside Emacs in
case you do save later.  It also marks the buffer as ``modified'' so that C-x
C-s in that buffer will save.

 If you wish to mark the buffer as visiting a different file and save it right
away, use C-x C-w (write-file).  It is precisely equivalent to
set-visited-file-name followed by C-x C-s. C-x C-s used on a buffer that is not
visiting with a file has the same effect as C-x C-w; that is, it reads a file
name, marks the buffer as visiting that file, and saves it there.  The default
file name in a buffer that is not visiting a file is made by combining the
buffer name with the buffer's default directory.

 If Emacs is about to save a file and sees that the date of the latest version
on disk does not match what Emacs last read or wrote, Emacs notifies you of
this fact, because it probably indicates a problem caused by simultaneous
editing and requires your immediate attention. See Simultaneous Editing.

 If the variable require-final-newline is non-nil, Emacs puts a newline at the
end of any file that doesn't already end in one, every time a file is saved or
written.

 You can implement other ways to write files, and other things to be done
before writing them, using the variable write-file-hooks.  The value of this
variable should be a list of Lisp functions.  When a file is to be written, the
functions in the list are called, one by one, with no arguments.  If one of
them returns a non-nil value, Emacs takes this to mean that the file has been
written in some suitable fashion; the rest of the functions are not called, and
normal writing is not done.  If this variable is local to a buffer, changing
major modes does not clear it.  However, changing the visited file name does
clear this variable to nil.

 The list local-write-file-hooks is used just like write-file-hooks.  This list
is for use as a local variable.  It is a permanent local, so that switching
major modes does not affect it.

 The variable write-contents-hooks holds another list of functions to be called
before writing out a buffer to a file.  These functions are used just like the
ones in write-file-hooks.  The difference between this and write-file-hooks is
that changing the major mode does clear this variable, and setting the visited
file name does not clear it.

 The hook variables described here are not normal hooks, because the values
returned by the hook functions do matter.  This is why they have names ending
in `-hooks' rather than `-hook'.  See Hooks.


ΓòÉΓòÉΓòÉ 18.3.1. Backup Files ΓòÉΓòÉΓòÉ

 Because Unix does not provide version numbers in file names, rewriting a file
in Unix automatically destroys all record of what the file used to contain.
Thus, saving a file from Emacs throws away the old contents of the file---or it
would, except that Emacs carefully copies the old contents to another file,
called the backup file, before actually saving. (This assumes that the variable
make-backup-files is non-nil. Backup files are not written if this variable is
nil.)

 At your option, Emacs can keep either a single backup file or a series of
numbered backup files for each file that you edit.

 Emacs makes a backup for a file only the first time the file is saved from one
buffer.  No matter how many times you save a file, its backup file continues to
contain the contents from before the file was visited. Normally this means that
the backup file contains the contents from before the current editing session;
however, if you kill the buffer and then visit the file again, a new backup
file will be made by the next save.


ΓòÉΓòÉΓòÉ 18.3.1.1. Single or Numbered Backups ΓòÉΓòÉΓòÉ

 If you choose to have a single backup file (this is the default), the backup
file's name is constructed by appending `~' to the file name being edited;
thus, the backup file for `eval.c' would be `eval.c~'.

 If you choose to have a series of numbered backup files, backup file names are
made by appending `.~', the number, and another `~' to the original file name.
Thus, the backup files of `eval.c' would be called `eval.c.~1~', `eval.c.~2~',
and so on, through names like `eval.c.~259~' and beyond.

 If protection stops you from writing backup files under the usual names, the
backup file is written as `%backup%~' in your home directory. Only one such
file can exist, so only the most recently made such backup is available.

 The choice of single backup or numbered backups is controlled by the variable
version-control.  Its possible values are

t
          Make numbered backups.

nil
          Make numbered backups for files that have numbered backups already.
          Otherwise, make single backups.

never
          Do not in any case make numbered backups; always make single backups.

You can set version-control locally in an individual buffer to control the
making of backups for that buffer's file.  For example, Rmail mode locally sets
version-control to never to make sure that there is only one backup for an
Rmail file.  See Locals.

 If you set the environment variable VERSION_CONTROL, to tell various GNU
utilities what to do with backup files, Emacs also obeys the environment
variable by setting the Lisp variable version-control accordingly at startup.
If the environment variable's value is `t' or `numbered', then version-control
becomes t; if the value is `nil' or `existing', then version-control becomes
nil; if it is `never' or `simple', then version-control becomes never.


ΓòÉΓòÉΓòÉ 18.3.1.2. Automatic Deletion of Backups ΓòÉΓòÉΓòÉ

 To prevent unlimited consumption of disk space, Emacs can delete numbered
backup versions automatically.  Generally Emacs keeps the first few backups and
the latest few backups, deleting any in between.  This happens every time a new
backup is made.

 The two variables kept-old-versions and kept-new-versions control this
deletion.  Their values are, respectively the number of oldest
(lowest-numbered) backups to keep and the number of newest (highest-numbered)
ones to keep, each time a new backup is made.  Recall that these values are
used just after a new backup version is made; that newly made backup is
included in the count in kept-new-versions.  By default, both variables are 2.

 If trim-versions-without-asking is non-nil, the excess middle versions are
deleted without a murmur.  If it is nil, the default, then you are asked
whether the excess middle versions should really be deleted.

 Dired's . (Period) command can also be used to delete old versions. See Dired
Deletion.


ΓòÉΓòÉΓòÉ 18.3.1.3. Copying vs. Renaming ΓòÉΓòÉΓòÉ

 Backup files can be made by copying the old file or by renaming it.  This
makes a difference when the old file has multiple names.  If the old file is
renamed into the backup file, then the alternate names become names for the
backup file.  If the old file is copied instead, then the alternate names
remain names for the file that you are editing, and the contents accessed by
those names will be the new contents.

 The method of making a backup file may also affect the file's owner and group.
If copying is used, these do not change.  If renaming is used, you become the
file's owner, and the file's group becomes the default (different operating
systems have different defaults for the group).

 Having the owner change is usually a good idea, because then the owner always
shows who last edited the file.  Also, the owners of the backups show who
produced those versions.  Occasionally there is a file whose owner should not
change; it is a good idea for such files to contain local variable lists to set
backup-by-copying-when-mismatch locally (see File Variables).

 The choice of renaming or copying is controlled by three variables. Renaming
is the default choice.  If the variable backup-by-copying is non-nil, copying
is used.  Otherwise, if the variable backup-by-copying-when-linked is non-nil,
then copying is used for files that have multiple names, but renaming may still
used when the file being edited has only one name.  If the variable
backup-by-copying-when-mismatch is non-nil, then copying is used if renaming
would cause the file's owner or group to change.


ΓòÉΓòÉΓòÉ 18.3.2. Protection against Simultaneous Editing ΓòÉΓòÉΓòÉ

 Simultaneous editing occurs when two users visit the same file, both make
changes, and then both save them.  If nobody were informed that this was
happening, whichever user saved first would later find that his changes were
lost.  On some systems, Emacs notices immediately when the second user starts
to change the file, and issues an immediate warning.

 For the sake of systems where that is not possible, and in case someone else
proceeds to change the file despite the warning, Emacs also checks when the
file is saved, and issues a second warning if you are about to overwrite a file
containing another user's changes.  You can prevent loss of the other user's
work by taking the proper corrective action at that time.

 When you make the first modification in an Emacs buffer that is visiting a
file, Emacs records that  the file is locked by you.  (It does this by writing
another file in a directory reserved for this purpose.)  The lock is removed
when you save the changes.  The idea is that the file is locked whenever an
Emacs buffer visiting it has unsaved changes.

 If you begin to modify the buffer while the visited file is locked by someone
else, this constitutes a collision.  When Emacs detects a collision, it asks
you what to do, by calling the Lisp function ask-user-about-lock.  You can
redefine this function for the sake of customization.  The standard definition
of this function asks you a question and accepts three possible answers:

s
          Steal the lock.  Whoever was already changing the file loses the
          lock, and you gain the lock.

p
          Proceed.  Go ahead and edit the file despite its being locked by
          someone else.

q
          Quit.  This causes an error (file-locked) and the modification you
          were trying to make in the buffer does not actually take place.

 Note that locking works on the basis of a file name; if a file has multiple
names, Emacs does not realize that the two names are the same file and cannot
prevent two users from editing it simultaneously under different names.
However, basing locking on names means that Emacs can interlock the editing of
new files that will not really exist until they are saved.

 Some systems are not configured to allow Emacs to make locks.  On these
systems, Emacs cannot detect trouble in advance, but it still can detect the
collision when you try to save a file and overwrite someone else's changes.

 Every time Emacs saves a buffer, it first checks the last-modification date of
the existing file on disk to verify that it has not changed since the file was
last visited or saved.  If the date does not match, it implies that changes
were made in the file in some other way, and these changes are about to be lost
if Emacs actually does save.  To prevent this, Emacs prints a warning message
and asks for confirmation before saving. Occasionally you will know why the
file was changed and know that it does not matter; then you can answer yes and
proceed.  Otherwise, you should cancel the save with C-g and investigate the
situation.

 The first thing you should do when notified that simultaneous editing has
already taken place is to list the directory with C-u C-x C-d (see Directory
Listing).  This  shows the file's current author.  You should attempt to
contact him to warn him not to continue editing.  Often the next step is to
save the contents of your Emacs buffer under a different name, and use diff to
compare the two files.

 Simultaneous editing checks are also made when you visit with C-x C-f a file
that is already visited and when you start to modify a file.  This is not
strictly necessary, but it can cause you to find out about the collision
earlier, when perhaps correction takes less work.


ΓòÉΓòÉΓòÉ 18.4. Reverting a Buffer ΓòÉΓòÉΓòÉ

 If you have made extensive changes to a file and then change your mind about
them, you can get rid of them by reading in the previous version of the file.
To do this, use M-x revert-buffer, which operates on the current buffer.  Since
this is a very dangerous thing to do, you must confirm it with yes.

 revert-buffer keeps point at the same distance (measured in characters) from
the beginning of the file.  If the file was edited only slightly, you will be
at approximately the same piece of text after reverting as before.  If you have
made drastic changes, the same value of point in the old file may address a
totally different piece of text.

 Reverting marks the buffer as ``not modified'' until another change is made.

 Some kinds of buffers whose contents reflect data bases other than files, such
as Dired buffers, can also be reverted.  For them, reverting means
recalculating their contents from the appropriate data base.  Buffers created
randomly with C-x b cannot be reverted; revert-buffer reports an error when
asked to do so.


ΓòÉΓòÉΓòÉ 18.5. Auto-Saving: Protection Against Disasters ΓòÉΓòÉΓòÉ

 Emacs saves all the visited files from time to time (based on counting your
keystrokes) without being asked.  This is called auto-saving. It prevents you
from losing more than a limited amount of work if the system crashes.

 When Emacs determines that it is time for auto-saving, each buffer is
considered, and is auto-saved if auto-saving is turned on for it and it has
been changed since the last time it was auto-saved.  If any auto-saving is
done, the message `Auto-saving...' is displayed in the echo area until
auto-saving is finished.  Errors occurring during auto-saving are caught so
that they do not interfere with the execution of commands you have been typing.


ΓòÉΓòÉΓòÉ 18.5.1. Auto-Save Files ΓòÉΓòÉΓòÉ

 Auto-saving does not normally save in the files that you visited, because it
can be very undesirable to save a program that is in an inconsistent state when
you have made half of a planned change.  Instead, auto-saving is done in a
different file called the auto-save file, and the visited file is changed only
when you request saving explicitly (such as with C-x C-s).

 Normally, the auto-save file name is made by appending `#' to the front and
rear of the visited file name.  Thus, a buffer visiting file `foo.c' is
auto-saved in a file `#foo.c#'.  Most buffers that are not visiting files are
auto-saved only if you request it explicitly; when they are auto-saved, the
auto-save file name is made by appending `#%' to the front and `#' to the rear
of buffer name.  For example, the `*mail*' buffer in which you compose messages
to be sent is auto-saved in a file named `#%*mail*#'.  Auto-save file names are
made this way unless you reprogram parts of Emacs to do something different
(the functions make-auto-save-file-name and auto-save-file-name-p).  The file
name to be used for auto-saving in a buffer is calculated when auto-saving is
turned on in that buffer.

 If you want auto-saving to be done in the visited file, set the variable
auto-save-visited-file-name to be non-nil.  In this mode, there is really no
difference between auto-saving and explicit saving.

 A buffer's auto-save file is deleted when you save the buffer in its visited
file.  To inhibit this, set the variable delete-auto-save-files to nil.
Changing the visited file name with C-x C-w or set-visited-file-name renames
any auto-save file to go with the new visited name.

 When you delete a large amount of a buffer's text, auto-saving turns off in
that buffer.  This is because if you deleted the text unintentionally, you
might find the auto-save file more useful if it contains the deleted text.  To
restart auto-saving in that buffer, use M-x auto-save with a positive argument.


ΓòÉΓòÉΓòÉ 18.5.2. Controlling Auto-Saving ΓòÉΓòÉΓòÉ

 Each time you visit a file, auto-saving is turned on for that file's buffer if
the variable auto-save-default is non-nil (but not in batch mode; see Entering
Emacs).  The default for this variable is t, so auto-saving is the usual
practice for file-visiting buffers. Auto-saving can be turned on or off for any
existing buffer with the command M-x auto-save-mode.  Like other minor mode
commands, M-x auto-save-mode turns auto-saving on with a positive argument, off
with a zero or negative argument; with no argument, it toggles.

 Emacs does auto-saving periodically based on counting how many characters you
have typed since the last time auto-saving was done.  The variable
auto-save-interval specifies how many characters there are between auto-saves.
By default, it is 300.

 Auto-saving also takes place when you stop typing for a while.  The variable
auto-save-timeout says how many seconds Emacs should wait before it does an
auto save (and perhaps also a garbage collection).  (The actual time period is
longer if the current buffer is long; this is a heuristic which aims to keep
out of your way when you are editing long buffers in which auto-save takes an
appreciable amount of time.)  Auto-saving during idle periods accomplishes two
things: first, it makes sure all your work is saved if you go away from the
terminal for a while; second, it may avoid some auto-saving while you are
actually typing.

 Emacs also does auto-saving whenever it gets a fatal error.  This includes
killing the Emacs job with a shell command such as kill %emacs, or
disconnecting a phone line or network connection.

 You can request an auto-save explicitly with the command M-x do-auto-save.


ΓòÉΓòÉΓòÉ 18.5.3. Recovering Data from Auto-Saves ΓòÉΓòÉΓòÉ

 The way to use the contents of an auto-save file to recover from a loss of
data is with the command M-x recover-file RET file RET.  This visits file and
then (after your confirmation) restores the contents from from its auto-save
file `#file#'.  You can then save with C-x C-s to put the recovered text into
file itself.  For example, to recover file `foo.c' from its auto-save file
`#foo.c#', do:

M-x recover-file RET foo.c RET
yes RET
C-x C-s

 Before asking for confirmation, M-x recover-file displays a directory listing
describing the specified file and the auto-save file, so you can compare their
sizes and dates.  If the auto-save file is older, M-x recover-file does not
offer to read it.


ΓòÉΓòÉΓòÉ 18.6. File Name Aliases ΓòÉΓòÉΓòÉ

 Symbolic links and hard links both make it possible for several file names to
refer to the same file.  For example, when `foo' is a symbolic link to `bar',
the file has two names, but `bar' is the real name, and `foo' is just an alias.
More complex cases occur when symbolic links point to directories.

 If you visit two names for the same file, normally Emacs makes two different
buffers, but it warns you about the situation.

 If you wish to avoid visiting the same file in two buffers under different
names, set the variable find-file-existing-other-name to a non-nil value.  Then
find-file uses the existing buffer visiting the file, no matter which of the
file's names you specify.

 If the variable find-file-visit-truename is non-nil, then the file name
recorded for a buffer is the file's truename (made by replacing all symbolic
links with their target names), rather than the name you specify.  Setting
find-file-visit-truename also implies the effect of
find-file-existing-other-name.


ΓòÉΓòÉΓòÉ 18.7. Version Control ΓòÉΓòÉΓòÉ

 Version control systems are packages that can record multiple versions of a
source file, usually storing the unchanged parts of the file just once.
Version control systems also record history information such as the creation
time of each version, who created it, and a description of what was changed in
that version.

 The GNU project recommends the version control system known as RCS, which is
free software and available from the Free Software Foundation. Emacs supports
use of either RCS or SCCS (a proprietary, but widely used, version control
system that is not quite as powerful as RCS) through a facility called VC.  The
same Emacs commands work with either RCS or SCCS, so you hardly have to know
which one of them you are using.


ΓòÉΓòÉΓòÉ 18.7.1. Concepts of Version Control ΓòÉΓòÉΓòÉ

  When a file is under version control, we also say that it is registered in
the version control system.  Each registered file has a corresponding master
file which represents the file's present state plus its change history, so that
you can reconstruct from it either the current version or any specified earlier
version.  Usually the master file also records a log entry for each version
describing what was changed in that version.

 The file that is maintained under version control is sometimes called the work
file corresponding to its master file.

  To examine a file, you check it out.  This extracts a version of the source
file (typically, the most recent) from the master file. If you want to edit the
file, you must check it out locked.  Only one user can do this at a time for
any given source file.  (This kind of locking is completely unrelated to the
locking that Emacs uses to detect simultaneous editing of a file.)

 When you are done with your editing, you must check in the new version.  This
records the new version in the master file, and unlocks the source file so that
other people can lock it and thus modify it.

 Checkin and checkout are the basic operations of version control.  You can do
both of them with a single Emacs command: C-x C-q (vc-toggle-read-only).


ΓòÉΓòÉΓòÉ 18.7.2. Editing with Version Control ΓòÉΓòÉΓòÉ

 When you visit a file that is maintained using version control, the mode line
displays `RCS' or `SCCS' to inform you that version control is in use, and also
(in case you care) which low-level system the file is actually stored in.
Normally, such a source file is read-only, and the mode line indicates this
with `%%'.  With RCS, the mode line also indicates the head version, which is
normally also the version you are looking at.

 These are the commands for editing a file maintained with version control:

C-x C-q
          Check the visited file in or out.

C-x v u
          Revert the buffer and the file to the last checked in version.

C-x v c
          Remove the last-entered change from the master for the visited file.
          This undoes your last check-in.

C-x v i
          Register the visited file in version control.

(C-x v is the prefix key for version control commands; all of these commands
except for C-x C-q start with C-x v.)

 When you want to modify a file maintained with version control, type C-x C-q
(vc-toggle-read-only).  This checks out the file, and tells RCS or SCCS to lock
the file.  This means making the file writable for you (but not for anyone
else).  The mode line indicates that you have locked the file by showing your
name and a colon before the version number.

 When you are finished editing the file, type C-x C-q again. When used on a
file that is checked out, this command checks the file in.  But check-in does
not start immediately; first, you must enter the log entry---a description of
the changes in the new version. C-x C-q pops up a buffer for you to enter this
in.  When you are finished typing in the log entry, type C-c C-c to terminate
it; this is when actual check-in takes place.

 Once you have checked in your changes, the file is unlocked, so that other
users can lock it and modify it.

 Emacs does not save backup files for source files that are maintained with
version control.  If you want to make backup files despite version control, set
the variable vc-make-backup-files to a non-nil value.

 Normally the work file exists all the time, whether it is locked or not.  If
you set vc-keep-workfiles to nil, then checking in a new version with C-x C-q
deletes the work file; but any attempt to visit the file with Emacs creates it
again.

 It is not impossible to lock a file that someone else has locked.  If you try
to check out a file that is locked, C-x C-q asks you whether you want to
``steal the lock.''  If you say yes, the file becomes locked by you, but a
message is sent to the person who had formerly locked the file, to inform him
of what has happened.  The mode line indicates that a file is locked by someone
else by displaying the login name of that person, before the version number.

 If you want to discard your current set of changes and revert to the last
version checked in, use C-x v u (vc-revert-buffer). This cancels your last
check-out, leaving the file unlocked.  If you want to make a different set of
changes, you must first check the file out again.  C-x v u requires
confirmation, unless it sees that you haven't made any changes since the last
checked-in version.

 C-x v u is also the command to use if you lock a file and then don't actually
change it.

 You can cancel a change after checking it in, with C-x v c
(vc-cancel-version).  This command discards all record of the most recent
checked in version, so be careful about using it.  It requires confirmation
with yes.  By default, C-x v c reverts your workfile and buffer to the previous
version (the one that precedes the version that is deleted), but you can
prevent the reversion by giving the command a prefix argument.  Then the buffer
does not change.

 This command with a prefix argument is useful when you have checked in a
change and then discover a trivial error in it; you can cancel the erroneous
check-in, fix the error, and repeat the check-in.

 Be careful when invoking C-x v c, as it is easy to throw away a lot of work
with it.  To help you be careful, this command always asks for confirmation
with `yes'.

 You can register the visited file for version control using C-x v i
(vc-register).  This uses RCS if RCS is installed on your system; otherwise, it
uses SCCS.  After C-x v i, the file is unlocked and read-only.  Type C-x C-q if
you wish to edit it.

 By default, the initial version number is 1.1.  If you want to use a different
number, give C-x v i a prefix argument; then it reads the initial version
number using the minibuffer.

 If vc-initial-comment is non-nil, C-x v i reads an initial comment (much like
a log entry) to describe the purpose of this source file.


ΓòÉΓòÉΓòÉ 18.7.3. Variables Affecting Check-in and Check-out ΓòÉΓòÉΓòÉ

 If vc-suppress-confirm is non-nil, then C-x C-q and C-x v i can save the
current buffer without asking, and C-x v u also operates without asking for
confirmation. (This variable does not affect C-x v c; that is so drastic that
it should always ask for confirmation.)

 VC mode does much of its work by running the shell commands for RCS and SCCS.
If vc-command-messages is non-nil, VC displays messages to indicate which shell
commands it runs, and additional messages when the commands finish.

 Normally, VC assumes that it can deduce the locked/unlocked state of files by
looking at the file permissions of the work file; this is fast.  However, if
the `RCS' or `SCCS' subdirectory is actually a symbolic link, then VC does not
trust the file permissions to reflect this status.

You can specify the criterion for whether to trust the file permissions by
setting the variable vc-mistrust-permissions.  Its value may be t (always
mistrust the file permissions and check the master file), nil (always trust the
file permissions), or a function of one argument which makes the decision.  The
argument is the directory name of the `RCS' or `SCCS' subdirectory.  A non-nil
value from the function says to mistrust the file permissions.

 If you find that the file permissions of work files are changed erroneously,
set vc-mistrust-permissions to t.  Then VC always checks the master file to
determine the file's status.


ΓòÉΓòÉΓòÉ 18.7.4. Log Entries ΓòÉΓòÉΓòÉ

 When you're editing an initial comment or log entry for inclusion in a master
file, finish your entry by typing C-c C-c.

C-c C-c
          Finish the comment edit normally (vc-finish-logentry). This finishes
          check-in.

 To abort check-in, just don't type C-c C-c in that buffer.  You can switch
buffers and do other editing.  As long as you don't try to check in another
file, the entry you were editing remains in its buffer, and you can go back to
that buffer at any time to complete the check-in.

 If you change several source files for the same reason, it is often convenient
to specify the same log entry for many of the files.  To do this, use the
history of previous log entries.  The commands M-n, M-p, M-s and M-r for doing
this work just like the minibuffer history commands (except that these versions
are used outside the minibuffer).

 Each time you check in a file, the log entry buffer is put into VC Log mode,
which involves running two hooks: text-mode-hook and vc-log-mode-hook.  See
Hooks.


ΓòÉΓòÉΓòÉ 18.7.5. Change Logs and VC ΓòÉΓòÉΓòÉ

 If you use RCS for a program and also maintain a change log file for it (see
Change Log), you can generate change log entries automatically from the version
control log entries:

C-x v a
          Visit the current directory's change log file and create new entries
          for versions checked in since the most recent entry in the change log
          file (vc-update-change-log).

          This command works with RCS only; it does not work with SCCS.

 For example, suppose the first line of `ChangeLog' is dated 10 April 1992, and
that the only check-in since then was by Nathaniel Bowditch to `rcs2log' on 8
May 1992 with log text `Ignore log messages that start with `#'.'.  Then C-x v
a visits `ChangeLog' and inserts text like this:

Fri May  8 21:45:00 1992  Nathaniel Bowditch  ([e-mail])

        * rcs2log: Ignore log messages that start with `#'.

You can then edit the new change log entry further as you wish.

 Normally, the log entry for file `foo' is displayed as `* foo: text of log
entry'.  The `:' after `foo' is omitted if the text of the log entry starts
with `(functionname): '.  For example, if the log entry for `vc.el' is
`(vc-do-command): Check call-process status.', then the text in `ChangeLog'
looks like this:

Wed May  6 10:53:00 1992  Nathaniel Bowditch  ([e-mail])

        * vc.el (vc-do-command): Check call-process status.

 When C-x v a adds several change log entries at once, it groups related log
entries together if they all are checked in by the same author at nearly the
same time.  If the log entries for several such files all have the same text,
it coalesces them into a single entry. For example, suppose the most recent
checkins have the following log entries:

For `vc.texinfo':
Fix expansion typos.
For `vc.el':
Don't call expand-file-name.
For `vc-hooks.el':
Don't call expand-file-name.

 They appear like this in `ChangeLog':

Wed Apr  1 08:57:59 1992  Nathaniel Bowditch  ([e-mail])

        * vc.texinfo: Fix expansion typos.

        * vc.el, vc-hooks.el: Don't call expand-file-name.

 Normally, C-x v a separates log entries by a blank line, but you can mark
several related log entries to be clumped together (without an intervening
blank line) by starting the text of each related log entry with a label of the
form `{clumpname} '.  The label itself is not copied to `ChangeLog'.  For
example, suppose the log entries are:

For `vc.texinfo':
{expand} Fix expansion typos.
For `vc.el':
{expand} Don't call expand-file-name.
For `vc-hooks.el':
{expand} Don't call expand-file-name.

Then the text in `ChangeLog' looks like this:

Wed Apr  1 08:57:59 1992  Nathaniel Bowditch  ([e-mail])

        * vc.texinfo: Fix expansion typos.
        * vc.el, vc-hooks.el: Don't call expand-file-name.

 A log entry whose text begins with `#' is not copied to `ChangeLog'.  For
example, if you merely fix some misspellings in comments, you can log the
change with an entry beginning with `#' to avoid putting such trivia into
`ChangeLog'.


ΓòÉΓòÉΓòÉ 18.7.6. Comparing Versions ΓòÉΓòÉΓòÉ

 To compare two versions of a file, use the command C-x v = (vc-diff).

 Plain C-x v = compares the current buffer contents (saving them in the file if
necessary) with the last checked-in version of the file. With a prefix
argument, C-x v = reads a file name and two version numbers, then compares
those versions of the specified file.

 If you supply a directory name instead of the name of a work file, this
command compares the two specified versions of all registered files in that
directory and its subdirectories.  You can also specify a snapshot name (see
Snapshots) instead of one or both version numbers.

 You can specify a checked-in version by its number; you can specify the most
recent checked-in version with an empty version number.

 This command works by running the diff utility, getting the options from the
variable diff-switches.  It displays the output in a special buffer in another
window.  Unlike the M-x diff command, C-x v = does not try to find the changes
in the old and new versions.  This is because one or both versions normally do
not exist as files.  They exist only in the records of the master file. See
Comparing Files, for more information about M-x diff.


ΓòÉΓòÉΓòÉ 18.7.7. VC Status Commands ΓòÉΓòÉΓòÉ

 To view the detailed version control status and history of a file, type C-x v
l (vc-print-log).  It displays the history of changes to the current file,
including the text of the log entries.  The output appears in a separate
window.

 When you are working on a large program, it's often useful to find all the
files that are currently locked, or all the files maintained in version control
at all.  You can use C-x v d (vc-directory) to show all the locked files in or
beneath the current directory.  This includes all files that are locked by any
user.  C-u C-x v d lists all files in or beneath the current directory that are
maintained with version control.

 The list of files is displayed as a buffer that uses an augmented Dired mode.
The names of the users locking various files are shown (in parentheses) in
place of the owner and group.  All the normal Dired commands work in this
buffer.  Most interactive VC commands work also, and apply to the file name on
the current line.

 The vc-next-action command, when used in the augmented Dired buffer, operates
on all the marked files (or the file on the current line).  If it operates on
more than one file, it handles each file according to its current state; thus,
it may check in one file and check in another (which is already checked out).
If it has to check in any files, it reads a single log entry, then uses that
text for all the files being checked in.  This can be convenient for
registering or checking in several files at once, as part of the same change.


ΓòÉΓòÉΓòÉ 18.7.8. Renaming VC Work Files and Master Files ΓòÉΓòÉΓòÉ

 When you rename a registered file, you must also rename its master file
correspondingly to get proper results.  Use vc-rename-file to rename the source
file as you specify, and rename its master file accordingly.  It also updates
any snapshots (see Snapshots) that mention the file, so that they use the new
name; despite this, the snapshot thus modified may not completely work ( see
Snapshot Caveats).

 You cannot use vc-rename-file on a file that is locked by someone else.


ΓòÉΓòÉΓòÉ 18.7.9. Snapshots ΓòÉΓòÉΓòÉ

 A snapshot is a named set of file versions (one for each registered file) that
you can treat as a unit.  One important kind of snapshot is a release, a
(theoretically) stable version of the system that is ready for distribution to
users.


ΓòÉΓòÉΓòÉ 18.7.9.1. Making and Using Snapshots ΓòÉΓòÉΓòÉ

 There are two basic commands for snapshots; one makes a snapshot with a given
name, the other retrieves a named snapshot.

C-x v s name RET
          Define the last saved versions of every registered file in or under
          the current directory as a snapshot named name (vc-create-snapshot).

C-x v r name RET
          Check out all registered files at or below the current directory
          level using whatever versions correspond to the snapshot name
          (vc-retrieve-snapshot).

          This command reports an error if any files are locked at or below the
          current directory, without changing anything; this is to avoid
          overwriting work in progress.

 A snapshot uses a very small amount of resources---just enough to record the
list of file names and which version belongs to the snapshot.  Thus, you need
not hesitate to create snapshots whenever they are useful.

 You can give a snapshot name as an argument to C-x v = (see Comparing
Versions).  Thus, you can use it to compare a snapshot against the current
files, or two snapshots against each other, or a snapshot against a named
version.


ΓòÉΓòÉΓòÉ 18.7.9.2. Snapshot Caveats ΓòÉΓòÉΓòÉ

VC's snapshot facilities are modeled on RCS's named-configuration support.
They use RCS's native facilities for this, so under VC snapshots made using RCS
are visible even when you bypass VC.

For SCCS, VC implements snapshots itself.  The files it uses contain
name/file/version-number triples.  These snapshots are visible only through VC.

 File renaming and deletion can create some difficulties with snapshots. This
is not a VC-specific problem, but a general design issue in version control
systems that no one has solved very well yet.

 If you rename a registered file, you need to rename its master along with it
(the command vc-rename-file does this automatically).  If you are using SCCS,
you must also update the records of the snapshot, to mention the file by its
new name (vc-rename-file does this, too).  An old snapshot that refers to a
master file that no longer exists under the recorded name is invalid; VC can no
longer retrieve it.  It would be beyond the scope of this manual to explain
enough about RCS and SCCS to explain how to update the snapshots by hand.

 Using vc-rename-file makes the snapshot remain valid for retrieval, but it
does not solve all problems.  For example, some of the files in the program
probably refer to others by name.  At the very least, the makefile probably
mentions the file that you renamed.  If you retrieve an old snapshot, the
renamed file is retrieved under its new name, which is not the name that the
makefile expects.  So the program won't really work as retrieved.


ΓòÉΓòÉΓòÉ 18.7.10. Inserting Version Control Headers ΓòÉΓòÉΓòÉ

  Sometimes it is convenient to put version identification strings directly
into working files.  Certain special strings called version headers are
replaced in each successive version by the number of that version.

 You can use the C-x v h command (vc-insert-headers) to insert a suitable
header string.

C-x v h
          Insert headers in a file for use with your version-control system.

 The default header string is `$Id$' for RCS and `%W%' for SCCS.  You can
specify other headers to insert by setting the variable vc-header-alist.  Its
value is a list of elements of the form (program . string) where program is RCS
or SCCS and string is the string to use.

 Instead of a single string, you can specify a list of strings; then each
string in the list is inserted as a separate header on a line of its own.

 It is often necessary to use ``superfluous'' backslashes when writing the
strings that you put in this variable.  This is to prevent the string in the
constant from being interpreted as a header itself if the Emacs Lisp file
containing it is maintained with version control.

 Each header is inserted surrounded by tabs, inside comment delimiters, on a
new line at the start of the buffer.  Normally the ordinary comment start and
comment end strings of the current mode are used, but for certain modes, there
are special comment delimiters for this purpose; the variable vc-comment-alist
specifies them.  Each element of this list has the form (mode starter ender).

 The variable vc-static-header-alist specifies further strings to add based on
the name of the buffer.  Its value should be a list of elements of the form
(regexp . format).  Whenever regexp matches the buffer name, format is inserted
as part of the header.  A header line is inserted for each element that matches
the buffer name, and for each string specified by vc-header-alist.  The header
line is made by processing the string from vc-header-alist with the format
taken from the element.  The default value for vc-static-header-alist is:

(("\\.c$" .
  "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\
#endif /* lint */\n"))

which specifies insertion of a string of this form:


#ifndef lint
static char vcid[] = "string";
#endif /* lint */


ΓòÉΓòÉΓòÉ 18.8. Listing a File Directory ΓòÉΓòÉΓòÉ

 The file system groups files into directories.  A directory listing is a list
of all the files in a directory.  Emacs provides directory listings in brief
format (file names only) and verbose format (sizes, dates, and authors
included).

C-x C-d dir-or-pattern
          Print a brief directory listing (list-directory).

C-u C-x C-d dir-or-pattern
          Print a verbose directory listing.

 The command to display a directory listing is C-x C-d (list-directory).  It
reads using the minibuffer a file name which is either a directory to be listed
or a wildcard-containing pattern for the files to be listed.  For example,

C-x C-d /u2/emacs/etc RET

lists all the files in directory `/u2/emacs/etc'.  An example of specifying a
file name pattern is

C-x C-d /u2/emacs/src/*.c RET

 Normally, C-x C-d prints a brief directory listing containing just file names.
A numeric argument (regardless of value) tells it to print a verbose listing
(like `ls -l').

 The text of a directory listing is obtained by running ls in an inferior
process.  Two Emacs variables control the switches passed to ls:
list-directory-brief-switches is a string giving the switches to use in brief
listings ("-CF" by default), and list-directory-verbose-switches is a string
giving the switches to use in a verbose listing ("-l" by default).


ΓòÉΓòÉΓòÉ 18.9. Comparing Files ΓòÉΓòÉΓòÉ

 The command M-x diff compares two files, displaying the differences in an
Emacs buffer named `*Diff*'.  It works by running the diff program, using
options taken from the variable diff-switches, whose value should be a string.

 The buffer `*Diff*' has Compilation mode as its major mode, so you can use C-x
` to visit successive changed locations in the two source files.  You can also
move to a particular hunk of changes and type C-c C-c to find the corresponding
source location.  You can also use the other special commands of Compilation
mode: SPC and DEL for scrolling, and M-p and M-n for cursor motion. See
Compilation.

 The command M-x diff-backup compares a specified file with its most recent
backup.  If you specify the name of a backup file, diff-backup compares it with
the source file that it is a backup of.

 The command M-x compare-windows compares the text in the current window with
that in the next window.  Comparison starts at point in each window.  Point
moves forward in each window, a character at a time in each window, until the
next characters in the two windows are different.  Then the command is
finished.  For more information about windows in Emacs, Windows.

 With a numeric argument, compare-windows ignores changes in whitespace.  If
the variable compare-ignore-case is non-nil, it ignores differences in case as
well.

 See also Emerge, for convenient facilities for merging two similar files.


ΓòÉΓòÉΓòÉ 18.10. Miscellaneous File Operations ΓòÉΓòÉΓòÉ

 Emacs has commands for performing many other operations on files. All operate
on one file; they do not accept wild card file names.

 M-x view-file allows you to scan or read a file by sequential screenfuls.  It
reads a file name argument using the minibuffer.  After reading the file into
an Emacs buffer, view-file displays the beginning.  You can then type SPC to
scroll forward one windowful, or DEL to scroll backward.  Various other
commands are provided for moving around in the file, but none for changing it;
type C-h while viewing for a list of them.  They are mostly the same as normal
Emacs cursor motion commands.  To exit from viewing, type C-c. The commands for
viewing are defined by a special major mode called View mode.

 A related command, M-x view-buffer, views a buffer already present in Emacs.
See Misc Buffer.

 M-x insert-file inserts a copy of the contents of the specified file into the
current buffer at point, leaving point unchanged before the contents and the
mark after them.

 M-x write-region is the inverse of M-x insert-file; it copies the contents of
the region into the specified file.  M-x append-to-file adds the text of the
region to the end of the specified file.  See Accumulating Text.

 M-x delete-file deletes the specified file, like the rm command in the shell.
If you are deleting many files in one directory, it may be more convenient to
use Dired (see Dired).

 M-x rename-file reads two file names old and new using the minibuffer, then
renames file old as new.  If a file named new already exists, you must confirm
with yes or renaming is not done; this is because renaming causes the old
meaning of the name new to be lost.  If old and new are on different file
systems, the file old is copied and deleted.

 The similar command M-x add-name-to-file is used to add an additional name to
an existing file without removing its old name. The new name must belong on the
same file system that the file is on.

 M-x copy-file reads the file old and writes a new file named new with the same
contents.  Confirmation is required if a file named new already exists, because
copying has the consequence of overwriting the old contents of the file new.

 M-x make-symbolic-link reads two file names old and linkname, then creates a
symbolic link named linkname and pointing at old.  The effect is that future
attempts to open file linkname will refer to whatever file is named old at the
time the opening is done, or will get an error if the name old is not in use at
that time.  This command does not expand the argument filename, so that it
allows you to specify a relative name as the target of the link.

 Confirmation is required when creating the link if linkname is in use.  Note
that not all systems support symbolic links.


ΓòÉΓòÉΓòÉ 19. Using Multiple Buffers ΓòÉΓòÉΓòÉ

 The text you are editing in Emacs resides in an object called a buffer.  Each
time you visit a file, a buffer is created to hold the file's text.  Each time
you invoke Dired, a buffer is created to hold the directory listing.  If you
send a message with C-x m, a buffer named `*mail*' is used to hold the text of
the message.  When you ask for a command's documentation, that appears in a
buffer called `*Help*'.

 At any time, one and only one buffer is selected.  It is also called the
current buffer.  Often we say that a command operates on ``the buffer'' as if
there were only one; but really this means that the command operates on the
selected buffer (most commands do).

 When Emacs has multiple windows, each window has a chosen buffer which is
displayed there, but at any time only one of the windows is selected and its
chosen buffer is the selected buffer.  Each window's mode line displays the
name of the buffer that the window is displaying (see Windows).

 Each buffer has a name, which can be of any length, and you can select any
buffer by giving its name.  Most buffers are made by visiting files, and their
names are derived from the files' names.  But you can also create an empty
buffer with any name you want.  A newly started Emacs has a buffer named
`*scratch*' which can be used for evaluating Lisp expressions in Emacs.  The
distinction between upper and lower case matters in buffer names.

 Each buffer records individually what file it is visiting, whether it is
modified, and what major mode and minor modes are in effect in it (see Major
Modes).  Any Emacs variable can be made local to a particular buffer, meaning
its value in that buffer can be different from the value in other buffers.  See
Locals.


ΓòÉΓòÉΓòÉ 19.1. Creating and Selecting Buffers ΓòÉΓòÉΓòÉ

C-x b buffer RET
          Select or create a buffer named buffer (switch-to-buffer).

C-x 4 b buffer RET
          Similar, but select buffer in another window
          (switch-to-buffer-other-window).

 To select the buffer named bufname, type C-x b bufname RET.  This runs the
command switch-to-buffer with argument bufname.  You can use completion on an
abbreviation for the buffer name you want (see Completion).  An empty argument
to C-x b specifies the most recently selected buffer that is not displayed in
any window.

 Most buffers are created by visiting files, or by Emacs commands that want to
display some text, but you can also create a buffer explicitly by typing C-x b
bufname RET.  This makes a new, empty buffer which is not visiting any file,
and selects it for editing.  Such buffers are used for making notes to
yourself.  If you try to save one, you are asked for the file name to use.  The
new buffer's major mode is determined by the value of default-major-mode (see
Major Modes).

 Note that C-x C-f, and any other command for visiting a file, can also be used
to switch buffers.  See Visiting.


ΓòÉΓòÉΓòÉ 19.2. Listing Existing Buffers ΓòÉΓòÉΓòÉ

C-x C-b
          List the existing buffers (list-buffers).

 To print a list of all the buffers that exist, type C-x C-b.  Each line in the
list shows one buffer's name, major mode and visited file.  The buffers are
listed in the order, most recently visited first.

 `*' at the beginning of a line indicates the buffer is ``modified''. If
several buffers are modified, it may be time to save some with C-x s (see
Saving).  `%' indicates a read-only buffer.  `.' marks the selected buffer.
Here is an example of a buffer list:

 MR Buffer         Size  Mode           File
 -- ------         ----  ----           ----
.*  emacs.tex      383402 Texinfo       /u2/emacs/man/emacs.tex
    *Help*         1287  Fundamental
    files.el       23076 Emacs-Lisp     /u2/emacs/lisp/files.el
  % RMAIL          64042 RMAIL          /u/rms/RMAIL
 *% man            747   Dired          /u2/emacs/man/
    net.emacs      343885 Fundamental   /u/rms/net.emacs
    fileio.c       27691 C              /u2/emacs/src/fileio.c
    NEWS           67340 Text           /u2/emacs/etc/NEWS
    *scratch*      0     Lisp Interaction

Note that the buffer `*Help*' was made by a help request; it is not visiting
any file.  The buffer man was made by Dired on the directory `/u2/emacs/man/'.


ΓòÉΓòÉΓòÉ 19.3. Miscellaneous Buffer Operations ΓòÉΓòÉΓòÉ

C-x C-q
          Toggle read-only status of buffer (toggle-read-only).

M-x rename-buffer RET name RET
          Change the name of the current buffer.

M-x rename-uniquely
          Rename the current buffer by adding `<number>' to the end.

M-x view-buffer RET buffer RET
          Scroll through buffer buffer.

 A buffer can be read-only, which means that commands to change its contents
are not allowed.  The mode line indicates read-only buffers with `%%' near the
left margin.

 Read-only buffers are made by subsystems such as Dired and Rmail that have
special commands to operate on the text; also if you visit a file that is
protected so you cannot write it.  If you wish to make changes in a read-only
buffer, use the command C-x C-q (vc-toggle-read-only).  It makes a read-only
buffer writable, and makes a writable buffer read-only.  This works by setting
the variable buffer-read-only, which has a local value in each buffer and makes
the buffer read-only if its value is non-nil.

 If the file is maintained with version control, C-x C-q works through the
version control system to change the read-only status of the buffer.

 M-x rename-buffer changes the name of the current buffer.  Specify the new
name as a minibuffer argument.  There is no default.  If you specify a name
that is in use for some other buffer, an error happens and no renaming is done.

 M-x rename-uniquely renames the current buffer to a similar name with a
numeric suffix added to make it both different and unique.  This command does
not need an argument.  It is useful for creating multiple shell buffers: if you
rename the `*Shell*', then do M-x shell again, it makes a new shell buffer
named `*Shell*'; meanwhile, the old shell buffer continues to exist under its
altered name.  This method is also good for mail buffers, compilation buffers,
and any Emacs feature which creates a special buffer with a particular name.

 M-x view-buffer is much like M-x view-file ( see Misc File Ops) except that it
examines an already existing Emacs buffer. View mode provides commands for
scrolling through the buffer conveniently but not for changing it.  When you
exit View mode, the value of point that resulted from your perusal remains in
effect.

 The commands M-x append-to-buffer and M-x insert-buffer can be used to copy
text from one buffer to another. See Accumulating Text.


ΓòÉΓòÉΓòÉ 19.4. Killing Buffers ΓòÉΓòÉΓòÉ

 If you continue an Emacs session for a while, you may accumulate a large
number of buffers.  You may then find it convenient to kill the buffers you no
longer need.  On most operating systems, killing a buffer releases its space
back to the operating system so that other programs can use it.  There are
several commands for killing buffers:

C-x k bufname RET
          Kill buffer bufname (kill-buffer).

M-x kill-some-buffers
          Offer to kill each buffer, one by one.

 C-x k (kill-buffer) kills one buffer, whose name you specify in the
minibuffer.  The default, used if you type just RET in the minibuffer, is to
kill the current buffer.  If you kill the current buffer, another buffer is
selected; one that has been selected recently but does not appear in any window
now.  If you ask to kill a buffer that is modified (has unsaved editing), then
you must confirm with yes before the buffer is killed.

 The command M-x kill-some-buffers asks about each buffer, one by one.  An
answer of y means to kill the buffer.  Killing the current buffer or a buffer
containing unsaved changes selects a new buffer or asks for confirmation just
like kill-buffer.

 If you want to do something special every time a buffer is killed, you can add
hook functions to the hook kill-buffer-hook (see Hooks).


ΓòÉΓòÉΓòÉ 19.5. Operating on Several Buffers ΓòÉΓòÉΓòÉ

 The buffer-menu facility is like a ``Dired for buffers''; it allows you to
request operations on various Emacs buffers by editing an Emacs buffer
containing a list of them.  You can save buffers, kill them (here called
deleting them, for consistency with Dired), or display them.

M-x buffer-menu
          Begin editing a buffer listing all Emacs buffers.

 The command buffer-menu writes a list of all Emacs buffers into the buffer
`*Buffer List*', and selects that buffer in Buffer Menu mode.  The buffer is
read-only, and can be changed only through the special commands described in
this section.  The usual Emacs cursor motion commands can be used in the
`*Buffer List*' buffer.  The following commands apply to the buffer described
on the current line.

d
          Request to delete (kill) the buffer, then move down.  The request
          shows as a `D' on the line, before the buffer name.  Requested
          deletions take place when you type the x command.

C-d
          Like d but move up afterwards instead of down.

s
          Request to save the buffer.  The request shows as an `S' on the line.
          Requested saves take place when you type the x command. You may
          request both saving and deletion for the same buffer.

x
          Perform previously requested deletions and saves.

u
          Remove any request made for the current line, and move down.

DEL
          Move to previous line and remove any request made for that line.

 The d, s and u commands to add or remove flags also move down a line.  They
accept a numeric argument as a repeat count.

 These commands operate immediately on the buffer listed on the current line:

~
          Mark the buffer ``unmodified''.  The command ~ does this immediately
          when you type it.

%
          Toggle the buffer's read-only flag.  The command % does this
          immediately when you type it.

t
          Visit the buffer as a tag table.

 There are also commands to select another buffer or buffers:

q
          Quit the buffer menu---immediately display the most recent formerly
          visible buffer in its place.

f
          Immediately select this line's buffer in place of the `*Buffer List*'
          buffer.

o
          Immediately select this line's buffer in another window as if by C-x
          4 b, leaving `*Buffer List*' visible.

C-o
          Immediately display this line's buffer in another window, but don't
          select the window.

1
          Immediately select this line's buffer in a full-screen window.

2
          Immediately set up two windows, with this line's buffer in one, and
          the previously selected buffer (aside from the buffer `*Buffer
          List*') in the other.

m
          Mark this line's buffer to be displayed in another window if the q
          command is used.  The request shows as a `>' at the beginning of the
          line.  The same buffer may not have both a delete request and a
          display request.

v
          Immediately select this line's buffer, and also display in other
          windows any buffers previously marked with the m command.  If you
          have not marked any buffers, this command is equivalent to 1.

 All that buffer-menu does directly is create and select a suitable buffer, and
turn on Buffer Menu mode.  Everything else described above is implemented by
the special commands provided in Buffer Menu mode.  One consequence of this is
that you can switch from the `*Buffer List*' buffer to another Emacs buffer,
and edit there.  You can reselect the buffer-menu buffer later, to perform the
operations already requested, or you can kill it, or pay no further attention
to it.

 The only difference between buffer-menu and list-buffers is that buffer-menu
selects the `*Buffer List*' buffer and list-buffers does not.  If you run
list-buffers (that is, type C-x C-b) and select the buffer list manually, you
can use all of the commands described here.

 The buffer `*Buffer List*' is not updated automatically; its contents are just
text.  If you have created, deleted or renamed buffers, the way to update
`*Buffer List*' to show what you have done is to repeat the buffer-menu
command.


ΓòÉΓòÉΓòÉ 20. Multiple Windows ΓòÉΓòÉΓòÉ

 Emacs can split a frame into two or many windows.  Multiple windows can
display parts of different buffers, or different parts of one buffer.  Multiple
frames always imply multiple windows, because each window belongs to one and
only one frame.


ΓòÉΓòÉΓòÉ 20.1. Concepts of Emacs Windows ΓòÉΓòÉΓòÉ

 When multiple windows are being displayed, each window has an Emacs buffer
designated for display in it.  The same buffer may appear in more than one
window; if it does, any changes in its text are displayed in all the windows
where it appears.  But the windows showing the same buffer can show different
parts of it, because each window has its own value of point.

 At any time, one of the windows is the selected window; the buffer this window
is displaying is the current buffer.  The terminal's cursor shows the location
of point in this window.  Each other window has a location of point as well,
but since the terminal has only one cursor there is no way to show where those
locations are.  When you make multiple frames, each frame has a cursor which
appears in the frame's selected window.

 Commands to move point affect the value of point for the selected Emacs window
only.  They do not change the value of point in any other Emacs window, even
one showing the same buffer.  The same is true for commands such as C-x b to
change the selected buffer in the selected window; they do not affect other
windows at all.  However, there are other commands such as C-x 4 b that select
a different window and switch buffers in it.  Also, all commands that display
information in a window, including (for example) C-h f (describe-function) and
C-x C-b (list-buffers), work by switching buffers in a nonselected window
without affecting the selected window.

 When multiple windows show the same buffer, they can have different regions,
because they can have different values of point.  This means that in Transient
Mark mode, each window highlights a different part of the buffer.  The part
that is highlighted in the selected window is the region that editing commands
use.

 Each window has its own mode line, which displays the buffer name,
modification status and major and minor modes of the buffer that is displayed
in the window.  See Mode Line, for full details on the mode line.


ΓòÉΓòÉΓòÉ 20.2. Splitting Windows ΓòÉΓòÉΓòÉ

C-x 2
          Split the selected window into two windows, one above the other
          (split-window-vertically).

C-x 3
          Split the selected window into two windows positioned side by side
          (split-window-horizontally).

 The command C-x 2 (split-window-vertically) breaks the selected window into
two windows, one above the other.  Both windows start out displaying the same
buffer, with the same value of point.  By default the two windows each get half
the height of the window that was split; a numeric argument specifies how many
lines to give to the top window.

 C-x 3 (split-window-horizontally) breaks the selected window into two
side-by-side windows.  A numeric argument specifies how many columns to give
the one on the left.  A line of vertical bars separates the two windows.
Windows that are not the full width of the screen have mode lines, but they are
truncated; also, they do not always appear in inverse video, because the Emacs
display routines have not been taught how to display a region of inverse video
that is only part of a line on the screen.

 When a window is less than the full width, text lines too long to fit are
frequent.  Continuing all those lines might be confusing.  The variable
truncate-partial-width-windows can be set non-nil to force truncation in all
windows less than the full width of the screen, independent of the buffer being
displayed and its value for truncate-lines.  See Continuation Lines.

 Horizontal scrolling is often used in side-by-side windows. See Display.

 If split-window-keep-point is non-nil, C-x 2 tries to avoid shifting any text
on the screen by putting point in whichever window happens to contain the
screen line the cursor is already on.  The default is that
split-window-keep-point is non-nil on slow terminals.


ΓòÉΓòÉΓòÉ 20.3. Using Other Windows ΓòÉΓòÉΓòÉ

C-x o
          Select another window (other-window).  That is o, not zero.

C-M-v
          Scroll the next window (scroll-other-window).

M-x compare-windows
          Find next place where the text in the selected window does not match
          the text in the next window.

 To select a different window, use C-x o (other-window). That is an o, for
`other', not a zero.  When there are more than two windows, this command moves
through all the windows in a cyclic order, generally top to bottom and left to
right.  After the rightmost and bottommost window, it goes back to the one at
the upper left corner.  A numeric argument means to move several steps in the
cyclic order of windows.  A negative argument moves around the cycle in the
opposite order. When the minibuffer is active, the minibuffer is the last
window in the cycle; you can switch from the minibuffer window to one of the
other windows, and later switch back and finish supplying the minibuffer
argument that is requested.  See Minibuffer Edit.

 The usual scrolling commands (see Display) apply to the selected window only,
but there is one command to scroll the next window. C-M-v (scroll-other-window)
scrolls the window that C-x o would select.  It takes arguments, positive and
negative, like C-v.  (In the minibuffer, C-M-v scrolls the window that contains
the minibuffer help display, if any, rather than the next window in the
standard cyclic order.)

 The command M-x compare-windows lets you compare two files or buffers visible
in two windows, by moving through them to the next mismatch.  See Comparing
Files.


ΓòÉΓòÉΓòÉ 20.4. Displaying in Another Window ΓòÉΓòÉΓòÉ

 C-x 4 is a prefix key for commands that select another window (splitting the
window if there is only one) and select a buffer in that window.  Different C-x
4 commands have different ways of finding the buffer to select.

C-x 4 b bufname RET
          Select buffer bufname in another window.  This runs
          switch-to-buffer-other-window.

C-x 4 C-o bufname RET
          Display buffer bufname in another window, but don't select that
          buffer or that window.  This runs display-buffer.

C-x 4 f filename RET
          Visit file filename and select its buffer in another window.  This
          runs find-file-other-window.  See Visiting.

C-x 4 d directory RET
          Select a Dired buffer for directory directory in another window. This
          runs dired-other-window.  See Dired.

C-x 4 m
          Start composing a mail message in another window.  This runs
          mail-other-window; its same-window analogue is C-x m (see Sending
          Mail).

C-x 4 .
          Find a tag in the current tag table in another window.  This runs
          find-tag-other-window, the multiple-window variant of M-. (see Tags).

C-x 4 r filename RET
          Visit file filename read-only, and select its buffer in another
          window.  This runs find-file-read-only-other-window. See Visiting.


ΓòÉΓòÉΓòÉ 20.5. Deleting and Rearranging Windows ΓòÉΓòÉΓòÉ

C-x 0
          Get rid of the selected window (delete-window).  That is a zero.

C-x 1
          Get rid of all windows except the selected one
          (delete-other-windows).

C-x ^
          Make selected window taller (enlarge-window).

C-x }
          Make selected window wider (enlarge-window-horizontally).

 To delete a window, type C-x 0 (delete-window).  (That is a zero.)  The space
occupied by the deleted window is given to an adjacent window (but not the
minibuffer window, even if that is active at the time).  Once a window is
deleted, its attributes are forgotten; only restoring a window configuration
can bring it back.  Deleting the window has no effect on the buffer it used to
display; the buffer continues to exist, and you can select it in any window
with C-x b.

 C-x 1 (delete-other-windows) is more powerful than C-x 0; it deletes all the
windows except the selected one (and the minibuffer); the selected window
expands to use the whole frame except for the echo area.

 To readjust the division of space among vertically adjacent windows, use C-x ^
(enlarge-window).  It makes the currently selected window get one line bigger,
or as many lines as is specified with a numeric argument.  With a negative
argument, it makes the selected window smaller.  C-x }
(enlarge-window-horizontally) makes the selected window wider by the specified
number of columns.  The extra screen space given to a window comes from one of
its neighbors, if that is possible.  If this makes any window too small, it is
deleted and its space is given to an adjacent window.  The minimum size is
specified by the variables window-min-height and window-min-width.


ΓòÉΓòÉΓòÉ 21. Frames and X Windows ΓòÉΓòÉΓòÉ

 When using the X Window System, you can create multiple windows at the X level
in a single Emacs session.  Each X window that belongs to Emacs displays a
frame which can contain one or several Emacs windows. A frame initially
contains a single general-purpose Emacs window which you can subdivide
vertically or horizontally into smaller windows.  A frame normally contains its
own echo area and minibuffer, but you can make frames that don't have
these---they use the echo area and minibuffer of another frame.

 Anything you do in one frame also affects the other frames.  For instance, if
you put text in the kill ring in one frame, you can yank it in another frame.
If you exit emacs through C-x C-c in one frame, it terminates all the frames.
To delete just one frame, use C-x 5 0.

 To avoid confusion, we reserve the word ``window'' for the subdivisions that
Emacs implements, and never use it to refer to a frame.


ΓòÉΓòÉΓòÉ 21.1. Mouse Commands ΓòÉΓòÉΓòÉ

mouse-1
          Move point to where you click (mouse-set-point). This is normally the
          left button.

drag-mouse-1
          Move point to where you release the mouse, and set the mark where you
          initially clicked the mouse (mouse-set-region).  Thus, you can
          specify both ends of the region.  In Transient Mark mode, the region
          highlighting appears and changes as you drag.

          If you move the mouse off the top or bottom of the window while
          dragging, the window scrolls at a steady rate until you move the
          mouse back into the window.  This way, you can mark regions that
          don't fit entirely on the screen.

mouse-2
          Yank the last kill text, where you click (mouse-yank-at-click). This
          is normally the middle button.

mouse-3
          Copy text to the kill ring (mouse-save-then-click).  This is normally
          the right button.  If you click it a second time at the same place,
          that kills the text.

          This operation applies to the text between point and the place where
          you click.

 Thus, to kill a section of text, you can press Mouse-1 at one end, then press
Mouse-3 twice at the other end.  To select the text for copying without
deleting it from the buffer, press Mouse-3 just once.  Then you can copy it
elsewhere by yanking it. See Killing.

 To yank the killed or copied text somewhere else, move the mouse there and
press Mouse-2.  See Yanking.

 To copy text to another X window, kill it or save it in the kill ring. Under
X, this also sets the primary selection.  Then use the ``paste'' or ``yank''
command of the program operating the other window to insert the text from the
selection.

 To copy text from another X window, use the ``cut'' or ``copy'' command of the
program operating the other window, to select the text you want. Then yank it
in Emacs with C-y or Mouse-2.


ΓòÉΓòÉΓòÉ 21.2. Creating Frames ΓòÉΓòÉΓòÉ

 The prefix key C-x 5 is analogous to C-x 4, with parallel subcommands.  The
difference is that C-x 5 commands create a new frame rather than just a new
window in the selected frame.  ( See Pop Up Window.)  Different C-x 4 commands
have different ways of finding the buffer to select.

C-x 5 b bufname RET
          Select buffer bufname in another window.  This runs
          switch-to-buffer-other-frame.

C-x 5 f filename RET
          Visit file filename and select its buffer in another frame.  This
          runs find-file-other-frame.  See Visiting.

C-x 5 d directory RET
          Select a Dired buffer for directory directory in another frame. This
          runs dired-other-frame.  See Dired.

C-x 5 m
          Start composing a mail message in another frame.  This runs
          mail-other-frame, and its same-frame version is C-x m. See Sending
          Mail.

C-x 5 .
          Find a tag in the current tag table in another frame.  This runs
          find-tag-other-frame, the multiple-frame variant of M-.. See Tags.

C-x 5 r filename RET
          Visit file filename read-only, and select its buffer in another
          frame.  This runs find-file-read-only-other-frame. See Visiting.


ΓòÉΓòÉΓòÉ 21.3. Setting Frame Parameters ΓòÉΓòÉΓòÉ

 This section describes commands for altering the display style and window
management behavior of the selected frame.

M-x set-foreground-color RET color RET
          Specify color color for the foreground of the selected frame.

M-x set-background-color RET color RET
          Specify color color for the background of the selected frame.

M-x set-cursor-color RET color RET
          Specify color color for the cursor of the selected frame.

M-x set-mouse-color RET color RET
          Specify color color for the mouse cursor when it is over the selected
          frame.

M-x set-border-color RET color RET
          Specify color color for the border of the selected frame.

M-x auto-raise-mode
          Toggle whether or not the selected frame should auto-raise.
          Auto-raise means that every time you move the mouse onto the frame,
          it raises the frame.

M-x auto-lower-mode
          Toggle whether or not the selected frame should auto-lower.
          Auto-lower means that every time you move the mouse off of the frame,
          the frame moves to the bottom of the stack of X windows.

M-x set-default-font RET font RET
          Specify font font as the default for the selected frame. See Font X,
          for ways to list the available fonts on your system.

          You can also set a frame's default font through a pop-up menu. Press
          C-Mouse-3 to activate this menu.


ΓòÉΓòÉΓòÉ 21.4. Scroll Bars ΓòÉΓòÉΓòÉ

 When using X, Emacs normally makes a scroll bar at the right of each Emacs
window.  The scroll bar runs the height of the window, and shows a moving
rectangular inner box which represents the portion of the buffer currently
displayed.  The entire height of the scroll bar represents the entire length of
the buffer.

 You can use Mouse-2 (normally, the middle button) in the scroll bar to move or
drag the inner box up and down.  If you move it to the top of the scroll bar,
you see the top of the buffer.  If you move it to the bottom of the scroll bar,
you see the bottom of the buffer.

 The left and right buttons in the scroll bar scroll by controlled increments.
Mouse-1 (normally, the left button) moves the line at the level where you click
up to the top of the window.  Mouse-3 (normally, the right button) moves the
line at the top of the window down to the level where you click.  By clicking
repeatedly in the same place, you can scroll by the same distance over and
over.

 You can enable or disable Scroll Bar mode with the command M-x
scroll-bar-mode.  With no argument, it toggles the use of scroll bars. With an
argument, it turns use of scroll bars on if and only if the argument is
positive.  This command applies to all frames, including frames yet to be
created.

 To enable or disable scroll bars for just the selected frame, use the M-x
toggle-scroll-bar command.


ΓòÉΓòÉΓòÉ 21.5. Menu Bars ΓòÉΓòÉΓòÉ

 By default, each Emacs frame has a menu bar at the top which you can use to
perform certain common operations.  There's no need to describe them in detail
here, as you can more easily see for yourself; also, we may change them and add
to them in subsequent Emacs versions.

 Each of the operations in the menu bar is bound to an ordinary Emacs command
which you can invoke equally well with M-x or with its own key bindings.  To
see the command's name and documentation, type C-h k and then select the menu
bar item you are interested in.

 You can turn display of menu bars on or off with M-x menu-bar-mode. With no
argument, this command toggles Menu Bar mode, a minor mode. With an argument,
the command turns Menu Bar mode on if the argument is positive, off if the
argument is not positive.


ΓòÉΓòÉΓòÉ 21.6. Using Multiple Typefaces ΓòÉΓòÉΓòÉ

 When using Emacs with X, you can set up multiple styles of displaying
characters.  The aspects of style that you can control are the type font, the
foreground color, the background color, and whether to underline.

 The way you control display style is by defining named faces. Each face can
specify a type font, a foreground color, a background color, and an underline
flag; but it does not have to specify all of them.

 The style of display used for a given character in the text is determined by
combining several faces.  Which faces to use is always set up by Lisp programs,
at present, by means of text properties and overlays.  Any aspect of the
display style that isn't specified by overlays or text properties comes from
the frame itself.

 To see what faces are currently defined, and what they look like, type M-x
list-faces-display.  It's possible for a given face to look different in
different frames; this command shows the appearance in the frame in which you
type it.

 When Transient Mark mode is enabled, the text of the region is highlighted
when the mark is active.  This uses a face named region; you can control the
style of highlighting by changing the style of this face with the commands
below.  See Setting Mark, for more information about Transient Mark mode and
activation and deactivation of the mark.

 Here are the commands for users to change the font of a face.

M-x set-face-font RET face RET font RET
          Use font font in face face.

M-x make-face-bold RET face RET
          Convert face face to use a bold version of its current font.

M-x make-face-italic RET face RET
          Convert face face to use a italic version of its current font.

M-x make-face-bold-italic RET face RET
          Convert face face to use a bold-italic version of its current font.

M-x make-face-unbold RET face RET
          Convert face face to use a non-bold version of its current font.

M-x make-face-unitalic RET face RET
          Convert face face to use a non-italic version of its current font.

 Here are the commands for users to set the colors and underline flag of a
face:

M-x set-face-foreground RET face RET color RET
          Use color color for the foreground of characters in face face.

M-x set-face-background RET face RET color RET
          Use color color for the background of characters in face face.

M-x set-face-underline-p RET face RET flag RET
          Specify whether to underline characters in face face.

M-x invert-face RET face RET
          Swap the foreground and background colors of face face.


ΓòÉΓòÉΓòÉ 21.7. Miscellaneous X Window Features ΓòÉΓòÉΓòÉ

 To iconify the selected Emacs frame, type C-z.  The normal meaning of C-z, to
suspend Emacs, is not useful under a window system, so it has a different
binding in that case (the command iconify-frame).

 To delete the selected frame, type C-x 5 0.

 Under X Windows, when Transient Mark mode is enabled, Emacs highlights the
region when the mark is active.  This is the main motive for using Transient
Mark mode.  To enable this mode, use the command M-x transient-mark-mode.  See
Mark.


ΓòÉΓòÉΓòÉ 22. Major Modes ΓòÉΓòÉΓòÉ

 Emacs provides many alternative major modes, each of which customizes Emacs
for editing text of a particular sort.  The major modes are mutually exclusive,
and each buffer has one major mode at any time. The mode line normally shows
the name of the current major mode, in parentheses (see Mode Line).

 The least specialized major mode is called Fundamental mode.  This mode has no
mode-specific redefinitions or variable settings, so that each Emacs command
behaves in its most general manner, and each option is in its default state.
For editing any specific type of text, such as Lisp code or English text, you
should switch to the appropriate major mode, such as Lisp mode or Text mode.

 Selecting a major mode changes the meanings of a few keys to become more
specifically adapted to the language being edited.  The ones which are changed
frequently are TAB, DEL, and LFD.  In addition, the commands which handle
comments use the mode to determine how comments are to be delimited.  Many
major modes redefine the syntactical properties of characters appearing in the
buffer.  See Syntax.

 The major modes fall into three major groups.  Lisp mode (which has several
variants), C mode, Fortran mode and others are for specific programming
languages.  Text mode, Nroff mode, TeX mode and Outline mode are for editing
English text.  The remaining major modes are not intended for use on users'
files; they are used in buffers created for specific purposes by Emacs, such as
Dired mode for buffers made by Dired (see Dired), and Mail mode for buffers
made by C-x m (see Sending Mail), and Shell mode for buffers used for
communicating with an inferior shell process ( see Interactive Shell).

 Most programming language major modes specify that only blank lines separate
paragraphs.  This is so that the paragraph commands remain useful. (See
Paragraphs.)  They also cause Auto Fill mode to use the definition of TAB to
indent the new lines it creates.  This is because most lines in a program are
usually indented.  (See Indentation.)


ΓòÉΓòÉΓòÉ 22.1. How Major Modes are Chosen ΓòÉΓòÉΓòÉ

 You can select a major mode explicitly for the current buffer, but most of the
time Emacs determines which mode to use based on the file name or on special
text in the file.

 Explicit selection of a new major mode is done with a M-x command. From the
name of a major mode, add -mode to get the name of a command to select that
mode.  Thus, you can enter Lisp mode by executing M-x lisp-mode.

 When you visit a file, Emacs usually chooses the right major mode based on the
file's name.  For example, files whose names end in `.c' are edited in C mode.
The correspondence between file names and major mode is controlled by the
variable auto-mode-alist.  Its value is a list in which each element has the
form

(regexp . mode-function)

For example, one element normally found in the list has the form ("\\.c$" .
c-mode), and it is responsible for selecting C mode for files whose names end
in `.c'.  (Note that `\\' is needed in Lisp syntax to include a `\' in the
string, which is needed to suppress the special meaning of `.' in regexps.)
The only practical way to change this variable is with Lisp code.

 You can specify which major mode should be used for editing a certain file by
a special sort of text in the first nonblank line of the file.  The mode name
should appear in this line both preceded and followed by `-*-'.  Other text may
appear on the line as well.  For example,

;-*-Lisp-*-

tells Emacs to use Lisp mode.  Such an explicit specification overrides any
defaulting based on the file name.  Note how the semicolon is used to make Lisp
treat this line as a comment.

 Another format of mode specification is

-*-Mode: modename;-*-

which allows you to specify local variables as well, like this:

-*- mode: modename; var: value; ... -*-

See File Variables, for more information about this.

 When you visit a file that does not specify a major mode to use, or when you
create a new buffer with C-x b, the variable default-major-mode specifies which
major mode to use.  Normally its value is the symbol fundamental-mode, which
specifies Fundamental mode.  If default-major-mode is nil, the major mode is
taken from the previously selected buffer.

 If you change the major mode of a buffer, you can go back to the major mode
Emacs would choose automatically: use the command M-x normal-mode to do this.
This is the same function that find-file calls to choose the major mode.  It
also processes the file's local variables list if any.


ΓòÉΓòÉΓòÉ 23. Indentation ΓòÉΓòÉΓòÉ

 This chapter describes the Emacs commands that add, remove, or adjust
indentation.

TAB
          Indent current line ``appropriately'' in a mode-dependent fashion.

LFD
          Perform RET followed by TAB (newline-and-indent).

M-^
          Merge two lines (delete-indentation).  This would cancel out the
          effect of LFD.

C-M-o
          Split line at point; text on the line after point becomes a new line
          indented to the same column that it now starts in (split-line).

M-m
          Move (forward or back) to the first nonblank character on the current
          line (back-to-indentation).

C-M-\
          Indent several lines to same column (indent-region).

C-x TAB
          Shift block of lines rigidly right or left (indent-rigidly).

M-i
          Indent from point to the next prespecified tab stop column
          (tab-to-tab-stop).

M-x indent-relative
          Indent from point to under an indentation point in the previous line.

 Most programming languages have some indentation convention.  For Lisp code,
lines are indented according to their nesting in parentheses.  The same general
idea is used for C code, though many details are different.

 Whatever the language, to indent a line, use the TAB command.  Each major mode
defines this command to perform the sort of indentation appropriate for the
particular language.  In Lisp mode, TAB aligns the line according to its depth
in parentheses.  No matter where in the line you are when you type TAB, it
aligns the line as a whole.  In C mode, TAB implements a subtle and
sophisticated indentation style that knows about many aspects of C syntax.

 In Text mode, TAB runs the command tab-to-tab-stop, which indents to the next
tab stop column.  You can set the tab stops with M-x edit-tab-stops.


ΓòÉΓòÉΓòÉ 23.1. Indentation Commands and Techniques ΓòÉΓòÉΓòÉ

 If you just want to insert a tab character in the buffer, you can type C-q
TAB.

 To move over the indentation on a line, do M-m (back-to-indentation).  This
command, given anywhere on a line, positions point at the first nonblank
character on the line.

 To insert an indented line before the current line, do C-a C-o TAB.  To make
an indented line after the current line, use C-e LFD.

 C-M-o (split-line) moves the text from point to the end of the line vertically
down, so that the current line becomes two lines. C-M-o first moves point
forward over any spaces and tabs.  Then it inserts after point a newline and
enough indentation to reach the same column point is on.  Point remains before
the inserted newline; in this regard, C-M-o resembles C-o.

 To join two lines cleanly, use the M-^ (delete-indentation) command.  It
deletes the indentation at the front of the current line, and the line boundary
as well, replacing them with a single space.  As a special case (useful for
Lisp code) the single space is omitted if the characters to be joined are
consecutive open parentheses or closing parentheses, or if the junction follows
another newline.  To delete just the indentation of a line, go to the beginning
of the line and use M-\ (delete-horizontal-space), which deletes all spaces and
tabs around the cursor.

 If you have a fill prefix, M-^ deletes the fill prefix if it appears after the
newline that is deleted.  See Fill Prefix.

 There are also commands for changing the indentation of several lines at once.
C-M-\ (indent-region) gives each line which begins in the region the ``usual''
indentation by invoking TAB at the beginning of the line.  A numeric argument
specifies the column to indent to, and each line is shifted left or right so
that its first nonblank character appears in that column.  C-x TAB
(indent-rigidly) moves all of the lines in the region right by its argument
(left, for negative arguments).  The whole group of lines moves rigidly
sideways, which is how the command gets its name.

 M-x indent-relative indents at point based on the previous line (actually, the
last nonempty line).  It inserts whitespace at point, moving point, until it is
underneath an indentation point in the previous line. An indentation point is
the end of a sequence of whitespace or the end of the line.  If point is
farther right than any indentation point in the previous line, the whitespace
before point is deleted and the first indentation point then applicable is
used.  If no indentation point is applicable even then, indent-relative runs
tab-to-tab-stop (see Tab Stops).

 indent-relative is the definition of TAB in Indented Text mode.  See Text.


ΓòÉΓòÉΓòÉ 23.2. Tab Stops ΓòÉΓòÉΓòÉ

 For typing in tables, you can use Text mode's definition of TAB,
tab-to-tab-stop.  This command inserts indentation before point, enough to
reach the next tab stop column.  If you are not in Text mode, this command can
be found on the key M-i.

 You can specify the tab stops used by M-i.  They are stored in a variable
called tab-stop-list, as a list of column-numbers in increasing order.

 The convenient way to set the tab stops is with M-x edit-tab-stops, which
creates and selects a buffer containing a description of the tab stop settings.
You can edit this buffer to specify different tab stops, and then type C-c C-c
to make those new tab stops take effect.  In the tab stop buffer, C-c C-c runs
the function edit-tab-stops-note-changes rather than its usual definition
save-buffer.  edit-tab-stops records which buffer was current when you invoked
it, and stores the tab stops back in that buffer; normally all buffers share
the same tab stops and changing them in one buffer affects all, but if you
happen to make tab-stop-list local in one buffer then edit-tab-stops in that
buffer will edit the local settings.

 Here is what the text representing the tab stops looks like for ordinary tab
stops every eight columns.

        :       :       :       :       :       :
0         1         2         3         4
0123456789012345678901234567890123456789012345678
To install changes, type C-c C-c

 The first line contains a colon at each tab stop.  The remaining lines are
present just to help you see where the colons are and know what to do.

 Note that the tab stops that control tab-to-tab-stop have nothing to do with
displaying tab characters in the buffer.  See Display Vars, for more
information on that.


ΓòÉΓòÉΓòÉ 23.3. Tabs vs. Spaces ΓòÉΓòÉΓòÉ

 Emacs normally uses both tabs and spaces to indent lines.  If you prefer, all
indentation can be made from spaces only.  To request this, set
indent-tabs-mode to nil.  This is a per-buffer variable; altering the variable
affects only the current buffer, but there is a default value which you can
change as well.  See Locals.

 There are also commands to convert tabs to spaces or vice versa, always
preserving the columns of all nonblank text.  M-x tabify scans the region for
sequences of spaces, and converts sequences of at least three spaces to tabs if
that can be done without changing indentation.  M-x untabify changes all tabs
in the region to appropriate numbers of spaces.


ΓòÉΓòÉΓòÉ 24. Commands for Human Languages ΓòÉΓòÉΓòÉ

 The term text has two widespread meanings in our area of the computer field.
One is data that is a sequence of characters.  Any file that you edit with
Emacs is text, in this sense of the word.  The other meaning is more
restrictive: a sequence of characters in a human language for humans to read
(possibly after processing by a text formatter), as opposed to a program or
commands for a program.

 Human languages have syntactic/stylistic conventions that can be supported or
used to advantage by editor commands: conventions involving words, sentences,
paragraphs, and capital letters.  This chapter describes Emacs commands for all
of these things.  There are also commands for filling, which means rearranging
the lines of a paragraph to be approximately equal in length.  The commands for
moving over and killing words, sentences and paragraphs, while intended
primarily for editing text, are also often useful for editing programs.

 Emacs has several major modes for editing human language text. If the file
contains text pure and simple, use Text mode, which customizes Emacs in small
ways for the syntactic conventions of text.  For text which contains embedded
commands for text formatters, Emacs has other major modes, each for a
particular text formatter.  Thus, for input to TeX, you would use TeX mode; for
input to nroff, Nroff mode.


ΓòÉΓòÉΓòÉ 24.1. Words ΓòÉΓòÉΓòÉ

 Emacs has commands for moving over or operating on words.  By convention, the
keys for them are all Meta characters.

M-f
          Move forward over a word (forward-word).

M-b
          Move backward over a word (backward-word).

M-d
          Kill up to the end of a word (kill-word).

M-DEL
          Kill back to the beginning of a word (backward-kill-word).

M-@
          Mark the end of the next word (mark-word).

M-t
          Transpose two words or drag a word across other words
          (transpose-words).

 Notice how these keys form a series that parallels the character-based C-f,
C-b, C-d, C-t and DEL.  M-@ is related to C-@, which is an alias for C-SPC.

 The commands M-f (forward-word) and M-b (backward-word) move forward and
backward over words.  These Meta characters are thus analogous to the
corresponding control characters, C-f and C-b, which move over single
characters in the text.  The analogy extends to numeric arguments, which serve
as repeat counts.  M-f with a negative argument moves backward, and M-b with a
negative argument moves forward.  Forward motion stops right after the last
letter of the word, while backward motion stops right before the first letter.

 M-d (kill-word) kills the word after point.  To be precise, it kills
everything from point to the place M-f would move to.  Thus, if point is in the
middle of a word, M-d kills just the part after point.  If some punctuation
comes between point and the next word, it is killed along with the word.  (If
you wish to kill only the next word but not the punctuation before it, simply
do M-f to get the end, and kill the word backwards with M-DEL.) M-d takes
arguments just like M-f.

 M-DEL (backward-kill-word) kills the word before point.  It kills everything
from point back to where M-b would move to.  If point is after the space in
`FOO, BAR', then `FOO, ' is killed.  (If you wish to kill just `FOO', do M-b
M-d instead of M-DEL.)

 M-t (transpose-words) exchanges the word before or containing point with the
following word.  The delimiter characters between the words do not move.  For
example, `FOO, BAR' transposes into `BAR, FOO' rather than `BAR FOO,'.  See
Transpose, for more on transposition and on arguments to transposition
commands.

 To operate on the next n words with an operation which applies between point
and mark, you can either set the mark at point and then move over the words, or
you can use the command M-@ (mark-word) which does not move point, but sets the
mark where M-f would move to.  M-@ accepts a numeric argument that says how
many words to scan for the place to put the mark.

 The word commands' understanding of syntax is completely controlled by the
syntax table.  Any character can, for example, be declared to be a word
delimiter.  See Syntax.


ΓòÉΓòÉΓòÉ 24.2. Sentences ΓòÉΓòÉΓòÉ

 The Emacs commands for manipulating sentences and paragraphs are mostly on
Meta keys, so as to be like the word-handling commands.

M-a
          Move back to the beginning of the sentence (backward-sentence).

M-e
          Move forward to the end of the sentence (forward-sentence).

M-k
          Kill forward to the end of the sentence (kill-sentence).

C-x DEL
          Kill back to the beginning of the sentence (backward-kill-sentence).

 The commands M-a and M-e (backward-sentence and forward-sentence) move to the
beginning and end of the current sentence, respectively.  They were chosen to
resemble C-a and C-e, which move to the beginning and end of a line.  Unlike
them, M-a and M-e if repeated or given numeric arguments move over successive
sentences.  Emacs assumes that the typist's convention is followed, and thus
considers a sentence to end wherever there is a `.', `?' or `!' followed by the
end of a line or two spaces, with any number of `)', `]', `'', or `"'
characters allowed in between.  A sentence also begins or ends wherever a
paragraph begins or ends.

 Neither M-a nor M-e moves past the newline or spaces beyond the sentence edge
at which it is stopping.

 Just as C-a and C-e have a kill command, C-k, to go with them, so M-a and M-e
have a corresponding kill command M-k (kill-sentence) which kills from point to
the end of the sentence.  With minus one as an argument it kills back to the
beginning of the sentence.  Larger arguments serve as a repeat count.

 There is a special command, C-x DEL (backward-kill-sentence) for killing back
to the beginning of a sentence, because this is useful when you change your
mind in the middle of composing text.

 The variable sentence-end controls recognition of the end of a sentence.  It
is a regexp that matches the last few characters of a sentence, together with
the whitespace following the sentence.  Its normal value is

"[.?!][]\"')]*\\($\\|\t\\|  \\)[ \t\n]*"

This example is explained in the section on regexps.  See Regexps.


ΓòÉΓòÉΓòÉ 24.3. Paragraphs ΓòÉΓòÉΓòÉ

 The Emacs commands for manipulating paragraphs are also Meta keys.

M-{
          Move back to previous paragraph beginning (backward-paragraph).

M-}
          Move forward to next paragraph end (forward-paragraph).

M-h
          Put point and mark around this or next paragraph (mark-paragraph).

 M-{ moves to the beginning of the current or previous paragraph, while M-}
moves to the end of the current or next paragraph. Blank lines and text
formatter command lines separate paragraphs and are not part of any paragraph.
Also, an indented line starts a new paragraph.

 In major modes for programs (as opposed to Text mode), paragraphs begin and
end only at blank lines.  This makes the paragraph commands continue to be
useful even though there are no paragraphs per se.

 When there is a fill prefix, then paragraphs are delimited by all lines which
don't start with the fill prefix.  See Filling.

 When you wish to operate on a paragraph, you can use the command M-h
(mark-paragraph) to set the region around it.  This command puts point at the
beginning and mark at the end of the paragraph point was in.  If point is
between paragraphs (in a run of blank lines, or at a boundary), the paragraph
following point is surrounded by point and mark.  If there are blank lines
preceding the first line of the paragraph, one of these blank lines is included
in the region.  Thus, for example, M-h C-w kills the paragraph around or after
point.

 The precise definition of a paragraph boundary is controlled by the variables
paragraph-separate and paragraph-start.  The value of paragraph-start is a
regexp that should match any line that either starts or separates paragraphs.
The value of paragraph-separate is another regexp that should match only lines
that separate paragraphs without being part of any paragraph.  Lines that start
a new paragraph and are contained in it must match both regexps.  For example,
normally paragraph-start is "^[ \t\n\f]" and paragraph-separate is "^[
\t\f]*$".

 Normally it is desirable for page boundaries to separate paragraphs. The
default values of these variables recognize the usual separator for pages.


ΓòÉΓòÉΓòÉ 24.4. Pages ΓòÉΓòÉΓòÉ

 Files are often thought of as divided into pages by the formfeed character
(ASCII control-L, octal code 014).  For example, if a file is printed on a line
printer, each page of the file, in this sense, will start on a new page of
paper.  Emacs treats a page-separator character just like any other character.
You can insert it with C-q C-l, or delete it with DEL.  Thus, you are free to
paginate your file or not.  However, since pages are often meaningful divisions
of the file, Emacs provides commands to move over them and operate on them.

C-x [
          Move point to previous page boundary (backward-page).

C-x ]
          Move point to next page boundary (forward-page).

C-x C-p
          Put point and mark around this page (or another page) (mark-page).

C-x l
          Count the lines in this page (count-lines-page).

 The C-x [ (backward-page) command moves point to immediately after the
previous page delimiter.  If point is already right after a page delimiter, it
skips that one and stops at the previous one.  A numeric argument serves as a
repeat count.  The C-x ] (forward-page) command moves forward past the next
page delimiter.

 The C-x C-p command (mark-page) puts point at the beginning of the current
page and the mark at the end.  The page delimiter at the end is included (the
mark follows it).  The page delimiter at the front is excluded (point follows
it).  This command can be followed by C-w to kill a page which is to be moved
elsewhere.  If it is inserted after a page delimiter, at a place where C-x ] or
C-x [ would take you, then the page will be properly delimited before and after
once again.

 A numeric argument to C-x C-p is used to specify which page to go to, relative
to the current one.  Zero means the current page.  One means the next page, and
-1 means the previous one.

 The C-x l command (count-lines-page) is good for deciding where to break a
page in two.  It prints in the echo area the total number of lines in the
current page, and then divides it up into those preceding the current line and
those following, as in

Page has 96 (72+25) lines

 Notice that the sum is off by one; this is correct if point is not at the
beginning of a line.

 The variable page-delimiter controls where pages begin.  Its value is a regexp
that matches the beginning of a line that separates pages.  The normal value of
this variable is "^\f", which matches a formfeed character at the beginning of
a line.


ΓòÉΓòÉΓòÉ 24.5. Filling Text ΓòÉΓòÉΓòÉ

 With Auto Fill mode, text can be filled (broken up into lines that fit in a
specified width) as you insert it.  If you alter existing text it may no longer
be properly filled; then you can use the explicit fill commands to fill the
paragraph again.


ΓòÉΓòÉΓòÉ 24.5.1. Auto Fill Mode ΓòÉΓòÉΓòÉ

 Auto Fill mode is a minor mode in which lines are broken automatically when
they become too wide.  Breaking happens only when you type a SPC or RET.

M-x auto-fill-mode
          Enable or disable Auto Fill mode.

SPC
RET
          In Auto Fill mode, break lines when appropriate.

 M-x auto-fill-mode turns Auto Fill mode on if it was off, or off if it was on.
With a positive numeric argument it always turns Auto Fill mode on, and with a
negative argument always turns it off.  You can see when Auto Fill mode is in
effect by the presence of the word `Fill' in the mode line, inside the
parentheses.  Auto Fill mode is a minor mode, turned on or off for each buffer
individually.  See Minor Modes.

 In Auto Fill mode, lines are broken automatically at spaces when they get
longer than the desired width.  Line breaking and rearrangement takes place
only when you type SPC or RET.  If you wish to insert a space or newline
without permitting line-breaking, type C-q SPC or C-q LFD (recall that a
newline is really a linefeed).  Also, C-o inserts a newline without line
breaking.

 Auto Fill mode works well with Lisp mode, because when it makes a new line in
Lisp mode it indents that line with TAB.  If a line ending in a comment gets
too long, the text of the comment is split into two comment lines.  Optionally
new comment delimiters are inserted at the end of the first line and the
beginning of the second so that each line is a separate comment; the variable
comment-multi-line controls the choice (see Comments).

 Auto Fill mode does not refill entire paragraphs.  It can break lines but
cannot merge lines.  So editing in the middle of a paragraph can result in a
paragraph that is not correctly filled.  The easiest way to make the paragraph
properly filled again is usually with the explicit fill commands. See Fill
Commands.

 Many users like Auto Fill mode and want to use it in all text files. The
section on init files says how to arrange this permanently for yourself. See
Init File.


ΓòÉΓòÉΓòÉ 24.5.2. Explicit Fill Commands ΓòÉΓòÉΓòÉ

M-q
          Fill current paragraph (fill-paragraph).

C-x f
          Set the fill column (set-fill-column).

M-x fill-region
          Fill each paragraph in the region (fill-region).

M-x fill-region-as-paragraph.
          Fill the region, considering it as one paragraph.

M-s
          Center a line.

 To refill a paragraph, use the command M-q (fill-paragraph).  This operates on
the paragraph that point is inside, or the one after point if point is between
paragraphs. Refilling works by removing all the line-breaks, then inserting new
ones where necessary.

 The command M-s (center-line) centers the current line within the current fill
column.  With an argument, it centers several lines individually and moves past
them.

 To refill many paragraphs, use M-x fill-region, which divides the region into
paragraphs and fills each of them.

 M-q and fill-region use the same criteria as M-h for finding paragraph
boundaries (see Paragraphs).  For more control, you can use M-x
fill-region-as-paragraph, which refills everything between point and mark.
This command deletes any blank lines within the region, so separate blocks of
text end up combined into one block.

 A numeric argument to M-q causes it to justify the text as well as filling it.
This means that extra spaces are inserted to make the right margin line up
exactly at the fill column.  To remove the extra spaces, use M-q with no
argument.  (Likewise for fill-region.)

 When adaptive-fill-mode is non-nil (which is normally the case), if you use
fill-region-as-paragraph on an indented paragraph and you don't have a fill
prefix, it uses the indentation of the second line of the paragraph as the fill
prefix.  The effect of adaptive filling is not noticeable in Text mode, because
an indented line counts as a paragraph starter and thus each line of an
indented paragraph is considered a paragraph of its own.  But you do notice the
effect in Indented Text mode and some other major modes.

 The maximum line width for filling is in the variable fill-column. Altering
the value of fill-column makes it local to the current buffer; until that time,
the default value is in effect.  The default is initially 70.  See Locals.

 The easiest way to set fill-column is to use the command C-x f
(set-fill-column).  With no argument, it sets fill-column to the current
horizontal position of point.  With a numeric argument, it uses that as the new
fill column.


ΓòÉΓòÉΓòÉ 24.5.3. The Fill Prefix ΓòÉΓòÉΓòÉ

 To fill a paragraph in which each line starts with a special marker (which
might be a few spaces, giving an indented paragraph), use the fill prefix
feature.  The fill prefix is a string which Emacs expects every line to start
with, and which is not included in filling.

C-x .
          Set the fill prefix (set-fill-prefix).

M-q
          Fill a paragraph using current fill prefix (fill-paragraph).

M-x fill-individual-paragraphs
          Fill the region, considering each change of indentation as starting a
          new paragraph.

M-x fill-nonuniform-paragraphs
          Fill the region, considering only paragraph-separator lines as
          starting a new paragraph.

 To specify a fill prefix, move to a line that starts with the desired prefix,
put point at the end of the prefix, and give the command C-x .
(set-fill-prefix).  That's a period after the C-x.  To turn off the fill
prefix, specify an empty prefix: type C-x . with point at the beginning of a
line.

 When a fill prefix is in effect, the fill commands remove the fill prefix from
each line before filling and insert it on each line after filling. The fill
prefix is also inserted on new lines made automatically by Auto Fill mode.
Lines that do not start with the fill prefix are considered to start
paragraphs, both in M-q and the paragraph commands; this is just right if you
are using paragraphs with hanging indentation (every line indented except the
first one).  Lines which are blank or indented once the prefix is removed also
separate or start paragraphs; this is what you want if you are writing
multi-paragraph comments with a comment delimiter on each line.

 For example, if fill-column is 40 and you set the fill prefix to `;; ', then
M-q in the following text

;; This is an
;; example of a paragraph
;; inside a Lisp-style comment.

produces this:

;; This is an example of a paragraph
;; inside a Lisp-style comment.

 The C-o command inserts the fill prefix on new lines it creates, when you use
it at the beginning of a line (see Blank Lines). Conversely, the command M-^
deletes the prefix (if it occurs) after the newline that it deletes (see
Indentation).

 You can use M-x fill-individual-paragraphs to set the fill prefix for each
paragraph automatically.  This command divides the region into paragraphs,
treating every change in the amount of indentation as the start of a new
paragraph, and fills each of these paragraphs.  Thus, all the lines in one
``paragraph'' have the same amount of indentation.  That indentation serves as
the fill prefix for that paragraph.

 M-x fill-nonuniform-paragraphs is a similar command that divides the region
into paragraphs in a different way.  It considers only paragraph-separating
lines (as defined by paragraph-separate) as starting a new paragraph.  Since
this means that the lines of one paragraph may have different amounts of
indentation, the fill prefix used is the smallest amount of indentation of any
of the lines of the paragraph.

 The fill prefix is stored in the variable fill-prefix.  Its value is a string,
or nil when there is no fill prefix.  This is a per-buffer variable; altering
the variable affects only the current buffer, but there is a default value
which you can change as well.  See Locals.


ΓòÉΓòÉΓòÉ 24.6. Case Conversion Commands ΓòÉΓòÉΓòÉ

 Emacs has commands for converting either a single word or any arbitrary range
of text to upper case or to lower case.

M-l
          Convert following word to lower case (downcase-word).

M-u
          Convert following word to upper case (upcase-word).

M-c
          Capitalize the following word (capitalize-word).

C-x C-l
          Convert region to lower case (downcase-region).

C-x C-u
          Convert region to upper case (upcase-region).

 The word conversion commands are the most useful.  M-l (downcase-word)
converts the word after point to lower case, moving past it.  Thus, repeating
M-l converts successive words. M-u (upcase-word) converts to all capitals
instead, while M-c (capitalize-word) puts the first letter of the word into
upper case and the rest into lower case.  All these commands convert several
words at once if given an argument.  They are especially convenient for
converting a large amount of text from all upper case to mixed case, because
you can move through the text using M-l, M-u or M-c on each word as
appropriate, occasionally using M-f instead to skip a word.

 When given a negative argument, the word case conversion commands apply to the
appropriate number of words before point, but do not move point. This is
convenient when you have just typed a word in the wrong case: you can give the
case conversion command and continue typing.

 If a word case conversion command is given in the middle of a word, it applies
only to the part of the word which follows point.  This is just like what M-d
(kill-word) does.  With a negative argument, case conversion applies only to
the part of the word before point.

 The other case conversion commands are C-x C-u (upcase-region) and C-x C-l
(downcase-region), which convert everything between point and mark to the
specified case.  Point and mark do not move.

 The region case conversion commands upcase-region and downcase-region are
normally disabled.  This means that they ask for confirmation if you try to use
them.  When you confirm, you may enable the command, which means it will not
ask for confirmation again. See Disabling.


ΓòÉΓòÉΓòÉ 24.7. Text Mode ΓòÉΓòÉΓòÉ

 When you edit files of text in a human language, it's more convenient to use
Text mode rather than Fundamental mode.  Invoke M-x text-mode to enter Text
mode.  In Text mode, TAB runs the function tab-to-tab-stop, which allows you to
use arbitrary tab stops set with M-x edit-tab-stops (see Tab Stops).  Features
concerned with comments in programs are turned off except when explicitly
invoked.  The syntax table is changed so that periods are not considered part
of a word, while apostrophes, backspaces and underlines are.

 A similar variant mode is Indented Text mode, intended for editing text in
which most lines are indented.  This mode defines TAB to run indent-relative
(see Indentation), and makes Auto Fill indent the lines it creates.  The result
is that normally a line made by Auto Filling, or by LFD, is indented just like
the previous line.  Use M-x indented-text-mode to select this mode.

 Entering Text mode or Indented Text mode runs the hook text-mode-hook.  Other
major modes related to Text mode also run this hook, followed by hooks of their
own; this includes Nroff mode, TeX mode, Outline mode and Mail mode.  Hook
functions on text-mode-hook can look at the value of major-mode to see which of
these modes is actually being entered.  See Hooks.


ΓòÉΓòÉΓòÉ 24.8. Outline Mode ΓòÉΓòÉΓòÉ

 Outline mode is a major mode much like Text mode but intended for editing
outlines.  It allows you to make parts of the text temporarily invisible so
that you can see just the overall structure of the outline.  Type M-x
outline-mode to switch to Outline mode as the major mode of the current buffer.
Type M-x outline-minor-mode to enable Outline mode as a minor mode in the
current buffer. When Outline minor mode is enabled, the C-c commands of Outline
mode replace those of the major mode.

 When a line is invisible in outline mode, it does not appear on the screen.
The screen appears exactly as if the invisible line were deleted, except that
an ellipsis (three periods in a row) appears at the end of the previous visible
line (only one ellipsis no matter how many invisible lines follow).

 All editing commands treat the text of the invisible line as part of the
previous visible line.  For example, C-n moves onto the next visible line.
Killing an entire visible line, including its terminating newline, really kills
all the following invisible lines along with it; yanking it all back yanks the
invisible lines and they remain invisible.

 Entering Outline mode runs the hook text-mode-hook followed by the hook
outline-mode-hook (see Hooks).


ΓòÉΓòÉΓòÉ 24.8.1. Format of Outlines ΓòÉΓòÉΓòÉ

 Outline mode assumes that the lines in the buffer are of two types: heading
lines and body lines.  A heading line represents a topic in the outline.
Heading lines start with one or more stars; the number of stars determines the
depth of the heading in the outline structure.  Thus, a heading line with one
star is a major topic; all the heading lines with two stars between it and the
next one-star heading are its subtopics; and so on.  Any line that is not a
heading line is a body line.  Body lines belong with the preceding heading
line.  Here is an example:

* Food

This is the body,
which says something about the topic of food.

** Delicious Food

This is the body of the second-level header.

** Distasteful Food

This could have
a body too, with
several lines.

*** Dormitory Food

* Shelter

A second first-level topic with its header line.

 A heading line together with all following body lines is called collectively
an entry.  A heading line together with all following deeper heading lines and
their body lines is called a subtree.

 You can customize the criterion for distinguishing heading lines by setting
the variable outline-regexp.  Any line whose beginning has a match for this
regexp is considered a heading line. Matches that start within a line (not at
the beginning) do not count. The length of the matching text determines the
level of the heading; longer matches make a more deeply nested level.  Thus,
for example, if a text formatter has commands `@chapter', `@section' and
`@subsection' to divide the document into chapters and sections, you could make
those lines count as heading lines by setting outline-regexp to
`"@chap\\|@\\(sub\\)*section"'. Note the trick: the two words `chapter' and
`section' are equally long, but by defining the regexp to match only `chap' we
ensure that the length of the text matched on a chapter heading is shorter, so
that Outline mode will know that sections are contained in chapters. This works
as long as no other command starts with `@chap'.

 Outline mode makes a line invisible by changing the newline before it into an
ASCII control-M (code 015).  Most editing commands that work on lines treat an
invisible line as part of the previous line because, strictly speaking, it is
part of that line, since there is no longer a newline in between.  When you
save the file in Outline mode, control-M characters are saved as newlines, so
the invisible lines become ordinary lines in the file.  But saving does not
change the visibility status of a line inside Emacs.


ΓòÉΓòÉΓòÉ 24.8.2. Outline Motion Commands ΓòÉΓòÉΓòÉ

 There are some special motion commands in Outline mode that move backward and
forward to heading lines.

C-c C-n
          Move point to the next visible heading line
          (outline-next-visible-heading).

C-c C-p
          Move point to the previous visible heading line
          (outline-previous-visible-heading).

C-c C-f
          Move point to the next visible heading line at the same level as the
          one point is on (outline-forward-same-level).

C-c C-b
          Move point to the previous visible heading line at the same level
          (outline-backward-same-level).

C-c C-u
          Move point up to a lower-level (more inclusive) visible heading line
          (outline-up-heading).

 C-c C-n (next-visible-heading) moves down to the next heading line.  C-c C-p
(previous-visible-heading) moves similarly backward.  Both accept numeric
arguments as repeat counts.  The names emphasize that invisible headings are
skipped, but this is not really a special feature.  All editing commands that
look for lines ignore the invisible lines automatically.

 More powerful motion commands understand the level structure of headings. C-c
C-f (outline-forward-same-level) and C-c C-b (outline-backward-same-level) move
from one heading line to another visible heading at the same depth in the
outline.  C-c C-u (outline-up-heading) moves backward to another heading that
is less deeply nested.


ΓòÉΓòÉΓòÉ 24.8.3. Outline Visibility Commands ΓòÉΓòÉΓòÉ

 The other special commands of outline mode are used to make lines visible or
invisible.  Their names all start with hide or show. Most of them fall into
pairs of opposites.  They are not undoable; instead, you can undo right past
them.  Making lines visible or invisible is simply not recorded by the undo
mechanism.

M-x hide-body
          Make all body lines in the buffer invisible.

M-x show-all
          Make all lines in the buffer visible.

C-c C-h
          Make everything under this heading invisible, not including this
          heading itself
           (hide-subtree).

C-c C-s
          Make everything under this heading visible, including body,
          subheadings, and their bodies (show-subtree).

M-x hide-leaves
          Make the body of this heading line, and of all its subheadings,
          invisible.

M-x show-branches
          Make all subheadings of this heading line, at all levels, visible.

C-c C-i
          Make immediate subheadings (one level down) of this heading line
          visible (show-children).

M-x hide-entry
          Make this heading line's body invisible.

M-x show-entry
          Make this heading line's body visible.

 Two commands that are exact opposites are M-x hide-entry and M-x show-entry.
They are used with point on a heading line, and apply only to the body lines of
that heading.  The subtopics and their bodies are not affected.

 Two more powerful opposites are C-c C-h (hide-subtree) and C-c C-s
(show-subtree).  Both expect to be used when point is on a heading line, and
both apply to all the lines of that heading's subtree: its body, all its
subheadings, both direct and indirect, and all of their bodies.  In other
words, the subtree contains everything following this heading line, up to and
not including the next heading of the same or higher rank.

 Intermediate between a visible subtree and an invisible one is having all the
subheadings visible but none of the body.  There are two commands for doing
this, depending on whether you want to hide the bodies or make the subheadings
visible.  They are M-x hide-leaves and M-x show-branches.

 A little weaker than show-branches is C-c C-i (show-children).  It makes just
the direct subheadings visible---those one level down.  Deeper subheadings
remain invisible, if they were invisible.

 Two commands have a blanket effect on the whole file.  M-x hide-body makes all
body lines invisible, so that you see just the outline structure. M-x show-all
makes all lines visible.  These commands can be thought of as a pair of
opposites even though M-x show-all applies to more than just body lines.

 You can turn off the use of ellipses at the ends of visible lines by setting
selective-display-ellipses to nil.  Then there is no visible indication of the
presence of invisible lines.


ΓòÉΓòÉΓòÉ 24.9. Mode ΓòÉΓòÉΓòÉ

 TeX is a powerful text formatter written by Donald Knuth; it is also free,
like GNU Emacs.  LaTeX is a simplified input format for TeX, implemented by TeX
macros; it comes with TeX.  SliTeX is a special form of LaTeX.

 Emacs has a special TeX mode for editing TeX input files. It provides
facilities for checking the balance of delimiters and for invoking TeX on all
or part of the file.

 TeX mode has three variants, Plain TeX mode, LaTeX mode, and SliTeX mode
(these three distinct major modes differ only slightly). They are designed for
editing the three different formats.  The command M-x tex-mode looks at the
contents of the buffer to determine whether the contents appear to be either
LaTeX input or SliTeX input; it then selects the appropriate mode.  If it can't
tell which is right (e.g., the buffer is empty), the variable tex-default-mode
controls which mode is used.

 When M-x tex-mode does not guess right, you can use the commands M-x
plain-tex-mode, M-x latex-mode, and M-x slitex-mode to select explicitly the
particular variants of TeX mode.


ΓòÉΓòÉΓòÉ 24.9.1. Editing Commands ΓòÉΓòÉΓòÉ

 Here are the special commands provided in TeX mode for editing the text of the
file.

"
          Insert, according to context, either ```' or `"' or `'''
          (tex-insert-quote).

LFD
          Insert a paragraph break (two newlines) and check the previous
          paragraph for unbalanced braces or dollar signs
          (tex-terminate-paragraph).

M-x validate-tex-region
          Check each paragraph in the region for unbalanced braces or dollar
          signs.

C-c {
          Insert `{}' and position point between them (tex-insert-braces).

C-c }
          Move forward past the next unmatched close brace (up-list).

 In TeX, the character `"' is not normally used; we use ```' to start a
quotation and `''' to end one.  To make editing easier under this formatting
convention, TeX mode overrides the normal meaning of the key " with a command
that inserts a pair of single-quotes or backquotes (tex-insert-quote).  To be
precise, this command inserts ```' after whitespace or an open brace, `"' after
a backslash, and `''' after any other character.

 If you need the character `"' itself in unusual contexts, use C-q to insert
it.  Also, " with a numeric argument always inserts that number of `"'
characters.

 In TeX mode, `$' has a special syntax code which attempts to understand the
way TeX math mode delimiters match.  When you insert a `$' that is meant to
exit math mode, the position of the matching `$' that entered math mode is
displayed for a second.  This is the same feature that displays the open brace
that matches a close brace that is inserted.  However, there is no way to tell
whether a `$' enters math mode or leaves it; so when you insert a `$' that
enters math mode, the previous `$' position is shown as if it were a match,
even though they are actually unrelated.

 TeX uses braces as delimiters that must match.  Some users prefer to keep
braces balanced at all times, rather than inserting them singly.  Use C-c {
(tex-insert-braces) to insert a pair of braces.  It leaves point between the
two braces so you can insert the text that belongs inside.  Afterward, use the
command C-c } (up-list) to move forward past the close brace.

 There are two commands for checking the matching of braces.  LFD
(tex-terminate-paragraph) checks the paragraph before point, and inserts two
newlines to start a new paragraph.  It prints a message in the echo area if any
mismatch is found.  M-x validate-tex-region checks a region, paragraph by
paragraph.  When it finds a paragraph that contains a mismatch, it displays
point at the beginning of the paragraph for a few seconds and pushes a mark at
that spot.  Scanning continues until the whole buffer has been checked or until
you type another key. The positions of the last several paragraphs with
mismatches can be found in the mark ring (see Mark Ring).

 Note that Emacs commands count square brackets and parentheses in TeX mode,
not just braces.  This is not strictly correct for the purpose of checking TeX
syntax.  However, parentheses and square brackets are likely to be used in text
as matching delimiters and it is useful for the various motion commands and
automatic match display to work with them.


ΓòÉΓòÉΓòÉ 24.9.2. La Editing Commands ΓòÉΓòÉΓòÉ

 LaTeX mode provides a few extra features not applicable to plain TeX.

C-c C-o
          Insert `\begin' and `\end' for LaTeX block and position point on a
          line between them. (tex-latex-block).

C-c C-e
          Close the last unended block for LaTeX (tex-close-latex-block).

 In LaTeX input, `\begin' and `\end' commands are used to group blocks of text.
To insert a `\begin' and a matching `\end' (on a new line following the
`\begin'), use C-c C-o (tex-latex-block).  A blank line is inserted between the
two, and point is left there.

 Emacs knows all of the standard LaTeX block names and will permissively
complete a partially entered block name (see Completion).  You can add your own
list of block names to those known by Emacs with the variable
latex-block-names.  For example, to add `theorem', `corollary', and `proof',
include the line

(setq latex-block-names '("theorem" "corollary" "proof"))

to your `.emacs' file.

 In LaTeX input, `\begin' and `\end' commands must balance. You can use C-c C-e
(tex-close-latex-block) to insert automatically a matching `\end' to match the
last unmatched `\begin'. The `\end' will be indented to match the corresponding
`\begin'. The `\end' will be followed by a newline if point is at the beginning
of a line.


ΓòÉΓòÉΓòÉ 24.9.3. Printing Commands ΓòÉΓòÉΓòÉ

 You can invoke TeX as an inferior of Emacs on either the entire contents of
the buffer or just a region at a time.  Running TeX in this way on just one
chapter is a good way to see what your changes look like without taking the
time to format the entire file.

C-c C-r
          Invoke TeX on the current region, together with the buffer's header
          (tex-region).

C-c C-b
          Invoke TeX on the entire current buffer (tex-buffer).

C-c TAB
          Invoke BibTeX on the current file (tex-bibtex-file).

C-c C-f
          Invoke TeX on the current file (tex-file).

C-c C-l
          Recenter the window showing output from the inferior TeX so that the
          last line can be seen (tex-recenter-output-buffer).

C-c C-k
          Kill the TeX subprocess (tex-kill-job).

C-c C-p
          Print the output from the last C-c C-r, C-c C-b, or C-c C-f command
          (tex-print).

C-c C-v
          Preview the output from the last C-c C-r, C-c C-b, or C-c C-f command
          (tex-view).

C-c C-q
          Show the printer queue (tex-show-print-queue).

 You can pass the current buffer through an inferior TeX by means of C-c C-b
(tex-buffer).  The formatted output appears in a temporary; to print it, type
C-c C-p (tex-print). Afterward use C-c C-q (tex-show-print-queue) to view the
progress of your output towards being printed. If your terminal has the ability
to display TeX output files, you can preview the output on the terminal with
C-c C-v (tex-view).

 You can specify the directory to use for running TeX by setting the variable
tex-directory.  "." is the default value.  If your environment variable
TEXINPUTS contains relative directory names, or if your files contains `\input'
commands with relative file names, then tex-directory must be "." or you will
get the wrong results.  Otherwise, it is safe to specify some other directory,
such as `/tmp'.

 If you want to specify which shell commands are used in the inferior TeX, you
can do so by setting the values of the variables tex-run-command,
latex-run-command, slitex-run-command, tex-dvi-print-command,
tex-dvi-view-command, and tex-show-queue-command.  You must set the value of
tex-dvi-view-command for your particular terminal; this variable has no default
value.  The other variables have default values that may (or may not) be
appropriate for your system.

 Normally, the file name given to these commands comes at the end of the
command string; for example, `latex filename'.  In some cases, however, the
file name needs to be embedded in the command; an example is when you need to
provide the file name as an argument to one command whose output is piped to
another.  You can specify where to put the file name with `*' in the command
string.  For example,

(setq tex-dvi-print-command "dvips -f * | lpr")

 The terminal output from TeX, including any error messages, appears in a
buffer called `*tex-shell*'.  If TeX gets an error, you can switch to this
buffer and feed it input (this works as in Shell mode; see Interactive Shell).
Without switching to this buffer you can scroll it so that its last line is
visible by typing C-c C-l.

 Type C-c C-k (tex-kill-job) to kill the TeX process if you see that its output
is no longer useful.  Using C-c C-b or C-c C-r also kills any TeX process still
running.

 You can also pass an arbitrary region through an inferior TeX by typing C-c
C-r (tex-region).  This is tricky, however, because most files of TeX input
contain commands at the beginning to set parameters and define macros, without
which no later part of the file will format correctly.  To solve this problem,
C-c C-r allows you to designate a part of the file as containing essential
commands; it is included before the specified region as part of the input to
TeX.  The designated part of the file is called the header.

 To indicate the bounds of the header in Plain TeX mode, you insert two special
strings in the file.  Insert `%**start of header' before the header, and
`%**end of header' after it.  Each string must appear entirely on one line, but
there may be other text on the line before or after.  The lines containing the
two strings are included in the header. If `%**start of header' does not appear
within the first 100 lines of the buffer, C-c C-r assumes that there is no
header.

 In LaTeX mode, the header begins with `\documentstyle' and ends with
`\begin{document}'.  These are commands that LaTeX requires you to use in any
case, so nothing special needs to be done to identify the header.

 The commands (tex-buffer) and (tex-region) do all of their work in a temporary
directory, and do not have available any of the auxiliary files needed by TeX
for cross-references; these commands are generally not suitable for running the
final copy in which all of the cross-references need to be correct.  When you
want the auxiliary files, use C-c C-f (tex-file) which runs TeX on the current
buffer's file, in that file's directory.  Before TeX runs, you will be asked
about saving any modified buffers.  Generally, you need to use (tex-file) twice
to get cross-references correct.

 For LaTeX files, you can use BibTeX to process the auxiliary file for the
current buffer's file.  BibTeX looks up bibliographic citations in a data base
and prepares the cited references for the bibliography section.  The command
C-c TAB (tex-bibtex-file) runs the shell command (tex-bibtex-command) to
produce a `.bbl' file for the current buffer's file.  Generally, you need to do
C-c C-f (tex-file) once to generate the `.aux' file, then do C-c TAB
(tex-bibtex-file), and then repeat C-c C-f (tex-file) twice more to get the
cross-references correct.

 Entering any kind of TeX mode runs the hooks text-mode-hook and tex-mode-hook.
Then it runs either plain-tex-mode-hook or latex-mode-hook, whichever is
appropriate.  For SliTeX files, it calls slitex-mode-hook. Starting the TeX
shell runs the hook tex-shell-hook. See Hooks.


ΓòÉΓòÉΓòÉ 24.9.4. Unix  Distribution ΓòÉΓòÉΓòÉ

TeX for Unix systems can be obtained from the University of Washington for a
distribution fee.

To order a full distribution, send $200.00 for a 1/2-inch 9-track 1600 bpi (tar
or cpio) tape reel, or $210.00 for a 1/4-inch 4-track QIC-24 (tar or cpio)
cartridge, payable to the University of Washington to:

Northwest Computing Support Center
DR-10, Thomson Hall 35
University of Washington
Seattle, Washington 98195

Purchase orders are acceptable, but there is an extra charge of $10.00, to pay
for processing charges.

For overseas orders please add $20.00 to the base cost for shipment via air
parcel post, or $30.00 for shipment via courier.

 The normal distribution is a tar tape, blocked 20, 1600 bpi, on an industry
standard 2400 foot half-inch reel.  The physical format for the 1/4 inch
streamer cartridges uses QIC-11, 8000 bpi, 4-track serpentine recording for the
SUN.  Also, System V tapes can be written in cpio format, blocked 5120 bytes,
ASCII headers.


ΓòÉΓòÉΓòÉ 24.10. Nroff Mode ΓòÉΓòÉΓòÉ

 Nroff mode is a mode like Text mode but modified to handle nroff commands
present in the text.  Invoke M-x nroff-mode to enter this mode.  It differs
from Text mode in only a few ways.  All nroff command lines are considered
paragraph separators, so that filling will never garble the nroff commands.
Pages are separated by `.bp' commands.  Comments start with
backslash-doublequote.  Also, three special commands are provided that are not
in Text mode:

M-n
          Move to the beginning of the next line that isn't an nroff command
          (forward-text-line).  An argument is a repeat count.

M-p
          Like M-n but move up (backward-text-line).

M-?
          Prints in the echo area the number of text lines (lines that are not
          nroff commands) in the region (count-text-lines).

 The other feature of Nroff mode is that you can turn on Electric Nroff mode.
This is a minor mode that you can turn on or off with M-x electric-nroff-mode
(see Minor Modes).  When the mode is on, each time you use RET to end a line
that contains an nroff command that opens a kind of grouping, the matching
nroff command to close that grouping is automatically inserted on the following
line.  For example, if you are at the beginning of a line and type . ( b RET,
this inserts the matching command `.)b' on a new line following point.

 Entering Nroff mode runs the hook text-mode-hook, followed by the hook
nroff-mode-hook (see Hooks).


ΓòÉΓòÉΓòÉ 25. Editing Programs ΓòÉΓòÉΓòÉ

 Emacs has many commands designed to understand the syntax of programming
languages such as Lisp and C.  These commands can

o Move over or kill balanced expressions or sexps (see Lists).

o Move over or mark top-level expressions---defuns, in Lisp; functions, in C
  (see Defuns).

o Show how parentheses balance (see Matching).

o Insert, kill or align comments (see Comments).

o Follow the usual indentation conventions of the language (see Program
  Indent).

 The commands for words, sentences and paragraphs are very useful in editing
code even though their canonical application is for editing human language
text.  Most symbols contain words (see Words); sentences can be found in
strings and comments (see Sentences). Paragraphs per se don't exist in code,
but the paragraph commands are useful anyway, because programming language
major modes define paragraphs to begin and end at blank lines (see Paragraphs).
Judicious use of blank lines to make the program clearer will also provide
interesting chunks of text for the paragraph commands to work on.

 The selective display feature is useful for looking at the overall structure
of a function (see Selective Display).  This feature causes only the lines that
are indented less than a specified amount to appear on the screen.


ΓòÉΓòÉΓòÉ 25.1. Major Modes for Programming Languages ΓòÉΓòÉΓòÉ

 Emacs also has major modes for the programming languages Lisp, Scheme (a
variant of Lisp), Awk, C, C++, Perl, Icon, Fortran and Muddle (another variant
of Lisp).  There is also a major mode for makefiles, called Makefile mode.

 Ideally, a major mode should be implemented for each programming language that
you might want to edit with Emacs; but often the mode for one language can
serve for other syntactically similar languages.  The language modes that exist
are those that someone decided to take the trouble to write.

 There are several forms of Lisp mode, which differ in the way they interface
to Lisp execution.  See Executing Lisp.

 Each of the programming language modes defines the TAB key to run an
indentation function that knows the indentation conventions of that language
and updates the current line's indentation accordingly.  For example, in C mode
TAB is bound to c-indent-line.  LFD is normally defined to do RET followed by
TAB; thus, it too indents in a mode-specific fashion.

 In most programming languages, indentation is likely to vary from line to
line.  So the major modes for those languages rebind DEL to treat a tab as if
it were the equivalent number of spaces (using the command
backward-delete-char-untabify).  This makes it possible to rub out indentation
one column at a time without worrying whether it is made up of spaces or tabs.
Use C-b C-d to delete a tab character before point, in these modes.

 Programming language modes define paragraphs to be separated only by blank
lines, so that the paragraph commands remain useful.  Auto Fill mode, if
enabled in a programming language major mode, indents the new lines which it
creates.

 Turning on a major mode runs a normal hook called the mode hook, which is the
value of a Lisp variable.  For example, turning on C mode runs the hook
c-mode-hook.  Mode hook variables for other programming language modes include
lisp-mode-hook, emacs-lisp-mode-hook, lisp-interaction-mode-hook,
scheme-mode-hook and muddle-mode-hook.  See Hooks.


ΓòÉΓòÉΓòÉ 25.2. Lists and Sexps ΓòÉΓòÉΓòÉ

 By convention, Emacs keys for dealing with balanced expressions are usually
Control-Meta characters.  They tend to be analogous in function to their
Control and Meta equivalents.  These commands are usually thought of as
pertaining to expressions in programming languages, but can be useful with any
language in which some sort of parentheses exist (including human languages).

 These commands fall into two classes.  Some deal only with lists
(parenthetical groupings).  They see nothing except parentheses, brackets,
braces (whichever ones must balance in the language you are working with), and
escape characters that might be used to quote those.

 The other commands deal with expressions or sexps.  The word `sexp' is derived
from s-expression, the ancient term for an expression in Lisp.  But in Emacs,
the notion of `sexp' is not limited to Lisp.  It refers to an expression in
whatever language your program is written in. Each programming language has its
own major mode, which customizes the syntax tables so that expressions in that
language count as sexps.

 Sexps typically include symbols, numbers, and string constants, as well as
anything contained in parentheses, brackets or braces.

 In languages that use prefix and infix operators, such as C, it is not
possible for all expressions to be sexps.  For example, C mode does not
recognize `foo + bar' as a sexp, even though it is a C expression; it
recognizes `foo' as one sexp and `bar' as another, with the `+' as punctuation
between them.  This is a fundamental ambiguity: both `foo + bar' and `foo' are
legitimate choices for the sexp to move over if point is at the `f'.  Note that
`(foo + bar)' is a single sexp in C mode.

 Some languages have obscure forms of syntax for expressions that nobody has
bothered to make Emacs understand properly.


ΓòÉΓòÉΓòÉ 25.3. List And Sexp Commands ΓòÉΓòÉΓòÉ

C-M-f
          Move forward over a sexp (forward-sexp).

C-M-b
          Move backward over a sexp (backward-sexp).

C-M-k
          Kill sexp forward (kill-sexp).

C-M-u
          Move up and backward in list structure (backward-up-list).

C-M-d
          Move down and forward in list structure (down-list).

C-M-n
          Move forward over a list (forward-list).

C-M-p
          Move backward over a list (backward-list).

C-M-t
          Transpose expressions (transpose-sexps).

C-M-@
          Put mark after following expression (mark-sexp).

 To move forward over a sexp, use C-M-f (forward-sexp).  If the first
significant character after point is an opening delimiter (`(' in Lisp; `(',
`[' or `{' in C), C-M-f moves past the matching closing delimiter.  If the
character begins a symbol, string, or number, C-M-f moves over that.

 The command C-M-b (backward-sexp) moves backward over a sexp.  The detailed
rules are like those above for C-M-f, but with directions reversed.  If there
are any prefix characters (single-quote, backquote and comma, in Lisp)
preceding the sexp, C-M-b moves back over them as well.  The sexp commands move
across comments as if they were whitespace in most modes.

 C-M-f or C-M-b with an argument repeats that operation the specified number of
times; with a negative argument, it moves in the opposite direction.

 Killing a sexp at a time can be done with C-M-k (kill-sexp). C-M-k kills the
characters that C-M-f would move over.

 The list commands move over lists like the sexp commands but skip blithely
over any number of other kinds of sexps (symbols, strings, etc). They are C-M-n
(forward-list) and C-M-p (backward-list).  The main reason they are useful is
that they usually ignore comments (since the comments usually do not contain
any lists).

 C-M-n and C-M-p stay at the same level in parentheses, when that's possible.
To move up one (or n) levels, use C-M-u (backward-up-list). C-M-u moves
backward up past one unmatched opening delimiter.  A positive argument serves
as a repeat count; a negative argument reverses direction of motion and also
requests repetition, so it moves forward and up one or more levels.

 To move down in list structure, use C-M-d (down-list).  In Lisp mode, where
`(' is the only opening delimiter, this is nearly the same as searching for a
`('.  An argument specifies the number of levels of parentheses to go down.

 A somewhat random-sounding command which is nevertheless handy is C-M-t
(transpose-sexps), which drags the previous sexp across the next one.  An
argument serves as a repeat count, and a negative argument drags backwards
(thus canceling out the effect of C-M-t with a positive argument).  An argument
of zero, rather than doing nothing, transposes the sexps ending after point and
the mark.

 To make the region be the next sexp in the buffer, use C-M-@ (mark-sexp) which
sets mark at the same place that C-M-f would move to.  C-M-@ takes arguments
like C-M-f.  In particular, a negative argument is useful for putting the mark
at the beginning of the previous sexp.

 The list and sexp commands' understanding of syntax is completely controlled
by the syntax table.  Any character can, for example, be declared to be an
opening delimiter and act like an open parenthesis. See Syntax.


ΓòÉΓòÉΓòÉ 25.4. Defuns ΓòÉΓòÉΓòÉ

 In Emacs, a parenthetical grouping at the top level in the buffer is called a
defun.  The name derives from the fact that most top-level lists in a Lisp file
are instances of the special form defun, but any top-level parenthetical
grouping counts as a defun in Emacs parlance regardless of what its contents
are, and regardless of the programming language in use.  For example, in C, the
body of a function definition is a defun.

C-M-a
          Move to beginning of current or preceding defun (beginning-of-defun).

C-M-e
          Move to end of current or following defun (end-of-defun).

C-M-h
          Put region around whole current or following defun (mark-defun).

 The commands to move to the beginning and end of the current defun are C-M-a
(beginning-of-defun) and C-M-e (end-of-defun).

 If you wish to operate on the current defun, use C-M-h (mark-defun) which puts
point at the beginning and mark at the end of the current or next defun.  For
example, this is the easiest way to get ready to move the defun to a different
place in the text.  In C mode, C-M-h runs the function mark-c-function, which
is almost the same as mark-defun; the difference is that it backs up over the
argument declarations, function name and returned data type so that the entire
C function is inside the region.  See Marking Objects.

 Emacs assumes that any open-parenthesis found in the leftmost column is the
start of a defun.  Therefore, *never put an open-parenthesis at the left margin
in a Lisp file unless it is the start of a top level list.  Never put an
open-brace or other opening delimiter at the beginning of a line of C code
unless it starts the body of a function.*  The most likely problem case is when
you want an opening delimiter at the start of a line inside a string.  To avoid
trouble, put an escape character (`\', in C and Emacs Lisp, `/' in some other
Lisp dialects) before the opening delimiter.  It will not affect the contents
of the string.

 In the remotest past, the original Emacs found defuns by moving upward a level
of parentheses until there were no more levels to go up.  This always required
scanning all the way back to the beginning of the buffer, even for a small
function.  To speed up the operation, Emacs was changed to assume that any `('
(or other character assigned the syntactic class of opening-delimiter) at the
left margin is the start of a defun.  This heuristic is nearly always right and
avoids the costly scan; however, it mandates the convention described above.


ΓòÉΓòÉΓòÉ 25.5. Indentation for Programs ΓòÉΓòÉΓòÉ

 The best way to keep a program properly indented is to use Emacs to re-indent
it as you change it.  Emacs has commands to indent properly either a single
line, a specified number of lines, or all of the lines inside a single
parenthetical grouping.


ΓòÉΓòÉΓòÉ 25.5.1. Basic Program Indentation Commands ΓòÉΓòÉΓòÉ

TAB
          Adjust indentation of current line.

LFD
          Equivalent to RET followed by TAB (newline-and-indent).

 The basic indentation command is TAB, which gives the current line the correct
indentation as determined from the previous lines.  The function that TAB runs
depends on the major mode; it is lisp-indent-line in Lisp mode, c-indent-line
in C mode, etc.  These functions understand different syntaxes for different
languages, but they all do about the same thing.  TAB in any programming
language major mode inserts or deletes whitespace at the beginning of the
current line, independent of where point is in the line.  If point is inside
the whitespace at the beginning of the line, TAB leaves it at the end of that
whitespace; otherwise, TAB leaves point fixed with respect to the characters
around it.

 Use C-q TAB to insert a tab at point.

 When entering a large amount of new code, use LFD (newline-and-indent), which
is equivalent to a RET followed by a TAB.  LFD creates a blank line, and then
gives it the appropriate indentation.

 TAB indents the second and following lines of the body of a parenthetical
grouping each under the preceding one; therefore, if you alter one line's
indentation to be nonstandard, the lines below will tend to follow it.  This is
the right behavior in cases where the standard result of TAB is unaesthetic.

 Remember that an open-parenthesis, open-brace or other opening delimiter at
the left margin is assumed by Emacs (including the indentation routines) to be
the start of a function.  Therefore, you must never have an opening delimiter
in column zero that is not the beginning of a function, not even inside a
string.  This restriction is vital for making the indentation commands fast;
you must simply accept it.  See Defuns, for more information on this.


ΓòÉΓòÉΓòÉ 25.5.2. Indenting Several Lines ΓòÉΓòÉΓòÉ

 When you wish to re-indent several lines of code which have been altered or
moved to a different level in the list structure, you have several commands
available.

C-M-q
          Re-indent all the lines within one list (indent-sexp).

C-u TAB
          Shift an entire list rigidly sideways so that its first line is
          properly indented.

C-M-\
          Re-indent all lines in the region (indent-region).

 You can re-indent the contents of a single list by positioning point before
the beginning of it and typing C-M-q (indent-sexp in Lisp mode, indent-c-exp in
C mode; also bound to other suitable commands in other modes).  The indentation
of the line the sexp starts on is not changed; therefore, only the relative
indentation within the list, and not its position, is changed.  To correct the
position as well, type a TAB before the C-M-q.

 If the relative indentation within a list is correct but the indentation of
its beginning is not, go to the line the list begins on and type C-u TAB.  When
TAB is given a numeric argument, it moves all the lines in the grouping
starting on the current line sideways the same amount that the current line
moves.  It is clever, though, and does not move lines that start inside
strings, or C preprocessor lines when in C mode.

 Another way to specify the range to be re-indented is with point and mark.
The command C-M-\ (indent-region) applies TAB to every line whose first
character is between point and mark.


ΓòÉΓòÉΓòÉ 25.5.3. Customizing Lisp Indentation ΓòÉΓòÉΓòÉ

 The indentation pattern for a Lisp expression can depend on the function
called by the expression.  For each Lisp function, you can choose among several
predefined patterns of indentation, or define an arbitrary one with a Lisp
program.

 The standard pattern of indentation is as follows: the second line of the
expression is indented under the first argument, if that is on the same line as
the beginning of the expression; otherwise, the second line is indented
underneath the function name.  Each following line is indented under the
previous line whose nesting depth is the same.

 If the variable lisp-indent-offset is non-nil, it overrides the usual
indentation pattern for the second line of an expression, so that such lines
are always indented lisp-indent-offset more columns than the containing list.

 The standard pattern is overridden for certain functions.  Functions whose
names start with def always indent the second line by lisp-body-indent extra
columns beyond the open-parenthesis starting the expression.

 The standard pattern can be overridden in various ways for individual
functions, according to the lisp-indent-hook property of the function name.
There are four possibilities for this property:

nil
          This is the same as no property; the standard indentation pattern is
          used.

defun
          The pattern used for function names that start with def is used for
          this function also.

a number, number
          The first number arguments of the function are distinguished
          arguments; the rest are considered the body of the expression.  A
          line in the expression is indented according to whether the first
          argument on it is distinguished or not.  If the argument is part of
          the body, the line is indented lisp-body-indent more columns than the
          open-parenthesis starting the containing expression.  If the argument
          is distinguished and is either the first or second argument, it is
          indented twice that many extra columns. If the argument is
          distinguished and not the first or second argument, the standard
          pattern is followed for that line.

a symbol, symbol
          symbol should be a function name; that function is called to
          calculate the indentation of a line within this expression.  The
          function receives two arguments:

   state
             The value returned by parse-partial-sexp (a Lisp primitive for
             indentation and nesting computation) when it parses up to the
             beginning of this line.

   pos
             The position at which the line being indented begins.

          It should return either a number, which is the number of columns of
          indentation for that line, or a list whose car is such a number.  The
          difference between returning a number and returning a list is that a
          number says that all following lines at the same nesting level should
          be indented just like this one; a list says that following lines
          might call for different indentations.  This makes a difference when
          the indentation is being computed by C-M-q; if the value is a number,
          C-M-q need not recalculate indentation for the following lines until
          the end of the list.


ΓòÉΓòÉΓòÉ 25.5.4. Customizing C Indentation ΓòÉΓòÉΓòÉ

 Two variables control which commands perform C indentation and when.

 If c-auto-newline is non-nil, newlines are inserted both before and after
braces that you insert, and after colons and semicolons. Correct C indentation
is done on all the lines that are made this way.

 If c-tab-always-indent is nil, the TAB command in C mode does indentation only
if point is at the left margin or within the line's indentation.  If there is
non-whitespace to the left of point, then TAB just inserts a tab character in
the buffer. Normally, this variable is t, and TAB always reindents the current
line.  The default behavior means that to insert a real tab character you must
quote it by typing C-q TAB.

 C does not have anything analogous to particular function names for which
special forms of indentation are desirable.  However, it has a different need
for customization facilities: many different styles of C indentation are in
common use.

 There are six variables you can set to control the style that Emacs C mode
uses.

c-indent-level
          Indentation of C statements within surrounding block.  The
          surrounding block's indentation is the indentation of the line on
          which the open-brace appears.

c-continued-statement-offset
          Extra indentation given to a substatement, such as the then-clause of
          an if or body of a while.

c-brace-offset
          Extra indentation for line if it starts with an open brace.

c-brace-imaginary-offset
          An open brace following other text is treated as if it were this far
          to the right of the start of its line.

c-argdecl-indent
          Indentation level of declarations of C function arguments.

c-label-offset
          Extra indentation for line that is a label, or case or default.

 The variable c-indent-level controls the indentation for C statements with
respect to the surrounding block.  In the example

    {
      foo ();

the difference in indentation between the lines is c-indent-level. Its standard
value is 2.

If the open-brace beginning the compound statement is not at the beginning of
its line, the c-indent-level is added to the indentation of the line, not the
column of the open-brace.  For example,

if (losing) {
  do_this ();

One popular indentation style is that which results from setting c-indent-level
to 8 and putting open-braces at the end of a line in this way.  I prefer to put
the open-brace on a separate line.

 In fact, the value of the variable c-brace-imaginary-offset is also added to
the indentation of such a statement.  Normally this variable is zero.  Think of
this variable as the imaginary position of the open brace, relative to the
first nonblank character on the line.  By setting this variable to 4 and
c-indent-level to 0, you can get this style:

if (x == y) {
    do_it ();
    }

 When c-indent-level is zero, the statements inside most braces will line up
right under the open brace.  But there is an exception made for braces in
column zero, such as surrounding a function's body.  The statements just inside
it do not go at column zero.  Instead, c-brace-offset and
c-continued-statement-offset (see below) are added to produce a typical offset
between brace levels, and the statements are indented that far.

 c-continued-statement-offset controls the extra indentation for a line that
starts within a statement (but not within parentheses or brackets).  These
lines are usually statements that are within other statements, such as the
then-clauses of if statements and the bodies of while statements.  This
parameter is the difference in indentation between the two lines in

if (x == y)
  do_it ();

Its standard value is 2.  Some popular indentation styles correspond to a value
of zero for c-continued-statement-offset.

 c-brace-offset is the extra indentation given to a line that starts with an
open-brace.  Its standard value is zero; compare

if (x == y)
  {

with

if (x == y)
  do_it ();

if c-brace-offset were set to 4, the first example would become

if (x == y)
      {

 c-argdecl-indent controls the indentation of declarations of the arguments of
a C function.  It is absolute: argument declarations receive exactly
c-argdecl-indent spaces.  The standard value is 5, resulting in code like this:

char *
index (string, c)
     char *string;
     int c;

 c-label-offset is the extra indentation given to a line that contains a label,
a case statement, or a default: statement.  Its standard value is -2, resulting
in code like this

switch (c)
  {
  case 'x':

If c-label-offset were zero, the same code would be indented as

switch (c)
  {
    case 'x':

This example assumes that the other variables above also have their standard
values.

 I strongly recommend that you try out the indentation style produced by the
standard settings of these variables, together with putting open braces on
separate lines.  You can see how it looks in all the C source files of GNU
Emacs.


ΓòÉΓòÉΓòÉ 25.6. Automatic Display Of Matching Parentheses ΓòÉΓòÉΓòÉ

 The Emacs parenthesis-matching feature is designed to show automatically how
parentheses match in the text.  Whenever you type a self-inserting character
that is a closing delimiter, the cursor moves momentarily to the location of
the matching opening delimiter, provided that is on the screen.  If it is not
on the screen, some text near it is displayed in the echo area.  Either way,
you can tell what grouping is being closed off.

 In Lisp, automatic matching applies only to parentheses.  In C, it applies to
braces and brackets too.  Emacs knows which characters to regard as matching
delimiters based on the syntax table, which is set by the major mode.  See
Syntax.

 If the opening delimiter and closing delimiter are mismatched---such as in
`[x)'---a warning message is displayed in the echo area.  The correct matches
are specified in the syntax table.

 Two variables control parenthesis match display.  blink-matching-paren turns
the feature on or off; nil turns it off, but the default is t to turn match
display on.  blink-matching-paren-distance specifies how many characters back
to search to find the matching opening delimiter.  If the match is not found in
that far, scanning stops, and nothing is displayed.  This is to prevent
scanning for the matching delimiter from wasting lots of time when there is no
match.  The default is 12,000.

 When using X Windows, you can request a more powerful kind of automatic
parenthesis matching by loading the paren library. To load it, type M-x
load-library RET paren RET. This library turns off the usual kind of matching
parenthesis display and substitutes another: whenever point is after a close
parenthesis, the close parenthesis and its matching open parenthesis are both
highlighted; otherwise, if point is before an open parenthesis, the matching
close parenthesis is highlighted.  (There is no need to highlight the open
parenthesis after point because the cursor appears on top of that character.)


ΓòÉΓòÉΓòÉ 25.7. Manipulating Comments ΓòÉΓòÉΓòÉ

 The comment commands insert, kill and align comments.

M-;
          Insert or align comment (indent-for-comment).

C-x ;
          Set comment column (set-comment-column).

C-u - C-x ;
          Kill comment on current line (kill-comment).

M-LFD
          Like RET followed by inserting and aligning a comment
          (indent-new-comment-line).

M-x comment-region
          Add or remove comment delimiters on all the lines in the region.

 The command that creates a comment is M-; (indent-for-comment). If there is no
comment already on the line, a new comment is created, aligned at a specific
column called the comment column.  The comment is created by inserting the
string Emacs thinks comments should start with (the value of comment-start; see
below).  Point is left after that string.  If the text of the line extends past
the comment column, then the indentation is done to a suitable boundary
(usually, at least one space is inserted).  If the major mode has specified a
string to terminate comments, that is inserted after point, to keep the syntax
valid.

 M-; can also be used to align an existing comment.  If a line already contains
the string that starts comments, then M-; just moves point after it and
re-indents it to the conventional place.  Exception: comments starting in
column 0 are not moved.

 Some major modes have special rules for indenting certain kinds of comments in
certain contexts.  For example, in Lisp code, comments which start with two
semicolons are indented as if they were lines of code, instead of at the
comment column.  Comments which start with three semicolons are supposed to
start at the left margin.  Emacs understands these conventions by indenting a
double-semicolon comment using TAB, and by not changing the indentation of a
triple-semicolon comment at all.

;; This function is just an example
;;; Here either two or three semicolons are appropriate.
(defun foo (x)
;;; And now, the first part of the function:
  ;; The following line adds one.
  (1+ x))           ; This line adds one.

 In C code, a comment preceded on its line by nothing but whitespace is
indented like a line of code.

 Even when an existing comment is properly aligned, M-; is still useful for
moving directly to the start of the comment.

 C-u - C-x ; (kill-comment) kills the comment on the current line, if there is
one.  The indentation before the start of the comment is killed as well.  If
there does not appear to be a comment in the line, nothing is done.  To
reinsert the comment on another line, move to the end of that line, do C-y, and
then do M-; to realign it.  Note that C-u - C-x ; is not a distinct key; it is
C-x ; (set-comment-column) with a negative argument.  That command is
programmed so that when it receives a negative argument it calls kill-comment.
However, kill-comment is a valid command which you could bind directly to a key
if you wanted to.

 The M-x comment-region command adds comment delimiters to the lines that start
in the region, thus commenting them out.  With a negative argument, it does the
opposite---it deletes comment delimiters from the lines in the region.

 With a positive argument, comment-region adds comment delimiters and
duplicates the last character of the comment start sequence as many times as
the argument specifies.  Thus, in Lisp mode, C-u 2 M-x comment-region adds `;;'
to each line.

 Duplicating the comment delimiter is a way of calling attention to the
comment.  It can also affect how the comment is indented.  In Lisp, for proper
indentation, you should use an argument of two, if between defuns, and three,
if within a defun.


ΓòÉΓòÉΓòÉ 25.7.1. Multiple Lines of Comments ΓòÉΓòÉΓòÉ

 If you are typing a comment and find that you wish to continue it on another
line, you can use the command M-LFD (indent-new-comment-line), which terminates
the comment you are typing, creates a new blank line afterward, and begins a
new comment indented under the old one.  When Auto Fill mode is on, going past
the fill column while typing a comment causes the comment to be continued in
just this fashion.  If point is not at the end of the line when M-LFD is typed,
the text on the rest of the line becomes part of the new comment line.


ΓòÉΓòÉΓòÉ 25.7.2. Options Controlling Comments ΓòÉΓòÉΓòÉ

 The comment column is stored in the variable comment-column.  You can set it
to a number explicitly.  Alternatively, the command C-x ; (set-comment-column)
sets the comment column to the column point is at.  C-u C-x ; sets the comment
column to match the last comment before point in the buffer, and then does a
M-; to align the current line's comment under the previous one.  Note that C-u
- C-x ; runs the function kill-comment as described above.

 The variable comment-column is per-buffer: setting the variable in the normal
fashion affects only the current buffer, but there is a default value which you
can change with setq-default. See Locals.  Many major modes initialize this
variable for the current buffer.

 The comment commands recognize comments based on the regular expression that
is the value of the variable comment-start-skip.  This regexp should not match
the null string.  It may match more than the comment starting delimiter in the
strictest sense of the word; for example, in C mode the value of the variable
is "/\\*+ *", which matches extra stars and spaces after the `/*' itself.
(Note that `\\' is needed in Lisp syntax to include a `\' in the string, which
is needed to deny the first star its special meaning in regexp syntax.  See
Regexps.)

 When a comment command makes a new comment, it inserts the value of
comment-start to begin it.  The value of comment-end is inserted after point,
so that it will follow the text that you will insert into the comment.  In C
mode, comment-start has the value "/* " and comment-end has the value " */".

 The variable comment-multi-line controls how M-LFD (indent-new-comment-line)
behaves when used inside a comment.  If comment-multi-line is nil, as it
normally is, then the comment on the starting line is terminated and a new
comment is started on the new following line.  If comment-multi-line is not
nil, then the new following line is set up as part of the same comment that was
found on the starting line.  This is done by not inserting a terminator on the
old line, and not inserting a starter on the new line.  In languages where
multi-line comments work, the choice of value for this variable is a matter of
taste.

 The variable comment-indent-function should contain a function that will be
called to compute the indentation for a newly inserted comment or for aligning
an existing comment.  It is set differently by various major modes.  The
function is called with no arguments, but with point at the beginning of the
comment, or at the end of a line if a new comment is to be inserted.  It should
return the column in which the comment ought to start.  For example, in Lisp
mode, the indent hook function bases its decision on how many semicolons begin
an existing comment, and on the code in the preceding lines.


ΓòÉΓòÉΓòÉ 25.8. Editing Without Unbalanced Parentheses ΓòÉΓòÉΓòÉ

M-(
          Put parentheses around next sexp(s) (insert-parentheses).

M-)
          Move past next close parenthesis and re-indent
          (move-over-close-and-reindent).

 The commands M-( (insert-parentheses) and M-) (move-over-close-and-reindent)
are designed to facilitate a style of editing which keeps parentheses balanced
at all times.  M-( inserts a pair of parentheses, either together as in `()',
or, if given an argument, around the next several sexps, and leaves point after
the open parenthesis.  Instead of typing ( F O O ), you can type M-( F O O,
which has the same effect except for leaving the cursor before the close
parenthesis.  Then you can type M-), which moves past the close parenthesis,
deleting any indentation preceding it (in this example there is none), and
indenting with LFD after it.


ΓòÉΓòÉΓòÉ 25.9. Completion for Symbol Names ΓòÉΓòÉΓòÉ

 Usually completion happens in the minibuffer.  But one kind of completion is
available in all buffers: completion for symbol names.

 The character M-TAB runs a command to complete the partial symbol before point
against the set of meaningful symbol names.  Any additional characters
determined by the partial name are inserted at point.

 If the partial name in the buffer has more than one possible completion and
they have no additional characters in common, a list of all possible
completions is displayed in another window.

 There are two ways of determining the set of legitimate symbol names to
complete against.  In most major modes, this uses a tag table (see Tags); the
legitimate symbol names are the tag names listed in the tag table file.  The
command which implements this is complete-tag.

 In Emacs-Lisp mode, the name space for completion normally consists of
nontrivial symbols present in Emacs---those that have function definitions,
values or properties.  However, if there is an open-parenthesis immediately
before the beginning of the partial symbol, only symbols with function
definitions are considered as completions. The command which implements this is
lisp-complete-symbol.


ΓòÉΓòÉΓòÉ 25.10. Documentation Commands ΓòÉΓòÉΓòÉ

 As you edit Lisp code to be run in Emacs, the commands C-h f
(describe-function) and C-h v (describe-variable) can be used to print
documentation of functions and variables that you want to call.  These commands
use the minibuffer to read the name of a function or variable to document, and
display the documentation in a window.

 For extra convenience, these commands provide default arguments based on the
code in the neighborhood of point.  C-h f sets the default to the function
called in the innermost list containing point.  C-h v uses the symbol name
around or adjacent to point as its default.

 Documentation on Unix commands, system calls and libraries can be obtained
with the M-x manual-entry command.  This reads a topic as an argument, and
displays the text on that topic from the Unix manual. manual-entry starts a
background process that formats the manual page, by running the man program.
The result goes in a buffer named `*man topic*'.  These buffers have a special
major mode that facilitates scrolling and examining other manual pages.

 Eventually the GNU project hopes to replace most man pages with
better-organized manuals that you can browse with Info. See Misc Help.  Since
this process is only partially completed, it is still useful to read manual
pages.


ΓòÉΓòÉΓòÉ 25.11. Change Logs ΓòÉΓòÉΓòÉ

 The Emacs command C-x 4 a adds a new entry to the change log file for the file
you are editing (add-change-log-entry-other-window).

 A change log file contains a chronological record of when and why you have
changed a program, consisting of a sequence of entries describing individual
changes.  Normally it is kept in a file called `ChangeLog' in the same
directory as the file you are editing, or one of its parent directories.  A
single `ChangeLog' file can record changes for all the files in its directory
and all its subdirectories.

 A change log entry starts with a header line that contains your name and the
current date.  Aside from these header lines, every line in the change log
starts with a space or a tab.  The bulk of the entry consists of items, each of
which starts with a line starting with whitespace and a star.  Here are two
entries, each with two items:

Wed May  5 14:11:45 1993  Richard Stallman  ([e-mail])

        * man.el: Rename functions and variables `man-*' to `Man-*'.
        (manual-entry): Make prompt string clearer.

        * simple.el (blink-matching-paren-distance): Change default to 12,000.

Tue May  4 12:42:19 1993  Richard Stallman  ([e-mail])

        * vc.el (minor-mode-map-alist): Don't use it if it's void.
        (vc-cancel-version): Doc fix.

 One entry can describe several changes; each change should have its own item.
Normally there should be a blank line between items.  When items are related
(parts of the same change, in different places), group them by leaving no blank
line between them.  The second entry above contains two items grouped in this
way.

 C-x 4 a visits the change log file and creates a new entry unless the most
recent entry is for today's date and your name.  It also creates a new item for
the current file.  For many languages, it can even guess the name of the
function or other object that was changed.

 The change log file is visited in Change Log mode.  Each bunch of grouped item
counts as one paragraph, and each entry is considered a page.  This facilitates
editing the entries.  LFD and auto-fill indent each new line like the previous
line; this is convenient for entering the contents of an entry.


ΓòÉΓòÉΓòÉ 25.12. Tag Tables ΓòÉΓòÉΓòÉ

 A tag table is a description of how a multi-file program is broken up into
files.  It lists the names of the component files and the names and positions
of the functions (or other named subunits) in each file.  Grouping the related
files makes it possible to search or replace through all the files with one
command.  Recording the function names and positions makes possible the M-.
command which you can use to find the definition of a function without having
to know which of the files it is in.

 Tag tables are stored in files called tag table files.  The conventional name
for a tag table file is `TAGS'.

 Each entry in the tag table records the name of one tag, the name of the file
that the tag is defined in (implicitly), and the position in that file of the
tag's definition.

 Just what names from the described files are recorded in the tag table depends
on the programming language of the described file.  They normally include all
functions and subroutines, and may also include global variables, data types,
and anything else convenient.  Each name recorded is called a tag.


ΓòÉΓòÉΓòÉ 25.12.1. Source File Tag Syntax ΓòÉΓòÉΓòÉ

 In Lisp code, any function defined with defun, any variable defined with
defvar or defconst, and in general the first argument of any expression that
starts with `(def' in column zero, is a tag.

 In Scheme code, tags include anything defined with def or with a construct
whose name starts with `def'.  They also include variables set with set! at top
level in the file.

 In C code, any C function is a tag, and so is any typedef if -t is specified
when the tag table is constructed.

 In Yacc or Bison input files, each rule defines as a tag the nonterminal it
constructs.  The portions of the file that contain C code are parsed as C code.

 In Fortran code, functions and subroutines are tags.

 In Prolog code, a tag name appears at the left margin.

 In assembler code, labels appearing at the beginning of a line, followed by a
colon, are tags.

 In LaTeX text, the argument of any of the commands \chapter, \section,
\subsection, \subsubsection, \eqno, \label, \ref, \cite, \bibitem and \typeout
is a tag.


ΓòÉΓòÉΓòÉ 25.12.2. Creating Tag Tables ΓòÉΓòÉΓòÉ

 The etags program is used to create a tag table file.  It knows the syntax of
several languages, as described in Tag Syntax. Here is how to run etags:

etags inputfiles...

The etags program reads the specified files, and writes a tag table named
`TAGS' in the current working directory.  etags recognizes the language used in
an input file based on its file name and contents; there are no switches for
specifying the language.  The -t switch tells etags to record typedefs in C
code as tags.

 If the tag table data become outdated due to changes in the files described in
the table, the way to update the tag table is the same way it was made in the
first place.  It is not necessary to do this often.

 If the tag table fails to record a tag, or records it for the wrong file, then
Emacs cannot possibly find its definition.  However, if the position recorded
in the tag table becomes a little bit wrong (due to some editing in the file
that the tag definition is in), the only consequence is a slight delay in
finding the tag.  Even if the stored position is very wrong, Emacs will still
find the tag, but it must search the entire file for it.

 So you should update a tag table when you define new tags that you want to
have listed, or when you move tag definitions from one file to another, or when
changes become substantial.  Normally there is no need to update the tag table
after each edit, or even every day.


ΓòÉΓòÉΓòÉ 25.12.3. Selecting a Tag Table ΓòÉΓòÉΓòÉ

 Emacs has at any time one selected tag table, and all the commands for working
with tag tables use the selected one.  To select a tag table, type M-x
visit-tags-table, which reads the tag table file name as an argument.  The name
`TAGS' in the default directory is used as the default file name.

 All this command does is store the file name in the variable tags-file-name.
Emacs does not actually read in the tag table contents until you try to use
them.  Setting this variable yourself is just as good as using
visit-tags-table.  The variable's initial value is nil; that value tells all
the commands for working with tag tables that they must ask for a tag table
file name to use.

 Using visit-tags-table to load a new tag table does not discard the other
tables previously loaded.  The other tags commands use all the tag tables that
are loaded; the first one they use is the one that mentions the current visited
file.

 You can specify a precise list of tag tables by setting the variable
tags-table-list to a list of strings, like this:

(setq tags-table-list
      '("~/emacs" "/usr/local/lib/emacs/src"))

This tells the tags commands to look at the `TAGS' files in your `~/emacs'
directory and in the `/usr/local/lib/emacs/src' directory.  The order depends
on which file you are in and which tags table mentions that file, as explained
above.


ΓòÉΓòÉΓòÉ 25.12.4. Finding a Tag ΓòÉΓòÉΓòÉ

 The most important thing that a tag table enables you to do is to find the
definition of a specific tag.

M-. tag RET
          Find first definition of tag (find-tag).

C-u M-.
          Find next alternate definition of last tag specified.

C-u - M-.
          Go back to previous tag found.

M-x find-tag-regexp RET pattern RET
          Find a tag whose name matches pattern.

C-u M-x find-tag-regexp
          Find the next tag whose name matches the last pattern used.

C-x 4 . tag RET
          Find first definition of tag, but display it in another window
          (find-tag-other-window).

C-x 5 . tag RET
          Find first definition of tag, and create a new frame to select the
          buffer (find-tag-other-frame).

 M-. (find-tag) is the command to find the definition of a specified tag.  It
searches through the tag table for that tag, as a string, and then uses the tag
table info to determine the file that the definition is in and the approximate
character position in the file of the definition.  Then find-tag visits that
file, moves point to the approximate character position, and searches
ever-increasing distances away to find the tag definition.

 If an empty argument is given (just type RET), the sexp in the buffer before
or around point is used as the tag argument. See Lists, for info on sexps.

 You don't need to give M-. the full name of the tag; a part will do.  This is
because M-. finds tags in the table which contain tag as a substring.  However,
it prefers an exact match to a substring match.

 To find other tags that match the same substring, give find-tag a numeric
argument, as in C-u M-.; this does not read a tag name, but continues searching
the tag table's text for another tag containing the same substring last used.
If you have a real META key, M-0 M-. is an easier alternative to C-u M-..

 Like most commands that can switch buffers, find-tag has a variant that
displays the new buffer in another window, and one that makes a new frame for
it.  The former is C-x 4 ., which invokes the command find-tag-other-window.
The latter is C-x 5 ., which invokes find-tag-other-frame.

 To move back to places you've found tags recently, use C-u - M-.; more
generally, M-. with a negative numeric argument.  This command can take you to
another buffer.  C-x 4 . with a negative argument finds the previous tag
location in another window.

 The new command M-x find-tag-regexp visits the tags that match a specified
regular expression.  It is just like M-. except that it does regexp matching
instead of substring matching.

 Emacs comes with a tag table file `src/TAGS' that includes all the Lisp
libraries and all the C sources of Emacs.  By specifying this file with
visit-tags-table and then using M-. you can quickly find the source for any
Emacs function.


ΓòÉΓòÉΓòÉ 25.12.5. Searching and Replacing with Tag Tables ΓòÉΓòÉΓòÉ

 The commands in this section visit and search all the files listed in the
selected tag table, one by one.  For these commands, the tag table serves only
to specify a sequence of files to search.  A related command is M-x grep (see
Compilation).

M-x tags-search
          Search for the specified regexp through the files in the selected tag
          table.

M-x tags-query-replace
          Perform a query-replace on each file in the selected tag table.

M-,
          Restart one of the commands above, from the current location of point
          (tags-loop-continue).

 M-x tags-search reads a regexp using the minibuffer, then searches for matches
in all the files in the selected tag table, one file at a time.  It displays
the name of the file being searched so you can follow its progress.  As soon as
it finds an occurrence, tags-search returns.

 Having found one match, you probably want to find all the rest.  To find one
more match, type M-, (tags-loop-continue) to resume the tags-search.  This
searches the rest of the current buffer, followed by the remaining files of the
tag table.

 M-x tags-query-replace performs a single query-replace through all the files
in the tag table.  It reads a regexp to search for and a string to replace
with, just like ordinary M-x query-replace-regexp.  It searches much like M-x
tags-search but repeatedly, processing matches according to your input.  See
Replace, for more information on query replace.

 It is possible to get through all the files in the tag table with a single
invocation of M-x tags-query-replace.  But since any unrecognized character
causes the command to exit, you may need to continue where you left off.  M-,
can be used for this.  It resumes the last tags search or replace command that
you did.

 The commands in this section carry out much broader searches than the
find-tags family.  The find-tags commands search only for definitions of tags
that match your substring or regexp.  The commands tags-search and
tags-query-replace find every occurrence of the regexp, as ordinary search
commands and replace commands do in the current buffer.

 These commands create buffers only temporarily for the files that they have to
search (those which are not already visited in Emacs buffers). Buffers in which
no match is found are quickly killed; the others continue to exist.

 It may have struck you that tags-search is a lot like grep. You can also run
grep itself as an inferior of Emacs and have Emacs show you the matching lines
one by one.  This works mostly the same as running a compilation and having
Emacs show you where the errors were. See Compilation.


ΓòÉΓòÉΓòÉ 25.12.6. Stepping Through a Tag Table ΓòÉΓòÉΓòÉ

 If you wish to process all the files in the selected tag table, but not in the
specific ways that M-x tags-search and M-x tags-query-replace do, you can use
M-x next-file to visit the files one by one.

C-u M-x next-file
          Visit the first file in the tag table, and prepare to advance
          sequentially by files.

M-x next-file
          Visit the next file in the selected tag table.


ΓòÉΓòÉΓòÉ 25.12.7. Tag Table Inquiries ΓòÉΓòÉΓòÉ

M-x list-tags
          Display a list of the tags defined in a specific program file.

M-x tags-apropos
          Display a list of all tags matching a specified regexp.

 M-x list-tags reads the name of one of the files described by the selected tag
table, and displays a list of all the tags defined in that file.  The ``file
name'' argument is really just a string to compare against the names recorded
in the tag table; it is read as a string rather than as a file name.
Therefore, completion and defaulting are not available, and you must enter the
string the same way it appears in the tag table.  Do not include a directory as
part of the file name unless the file name recorded in the tag table includes a
directory.

 M-x tags-apropos is like apropos for tags.  It reads a regexp, then finds all
the tags in the selected tag table whose entries match that regexp, and
displays the tag names found.

 You can also perform completion in the buffer on the name space of tag names
in the current tag tables.  See Symbol Completion.


ΓòÉΓòÉΓòÉ 25.13. Merging Files with Emerge ΓòÉΓòÉΓòÉ

It's not unusual for programmers to get their signals crossed and modify the
same program in two different directions.  To recover from this confusion, you
need to merge the two versions.  Emerge makes this easier.  See also Comparing
Files.


ΓòÉΓòÉΓòÉ 25.13.1. Overview of Emerge ΓòÉΓòÉΓòÉ

To start Emerge, run one of these four commands:

M-x emerge-files
          Merge two specified files.

M-x emerge-files-with-ancestor
          Merge two specified files, with reference to a common ancestor.

M-x emerge-buffers
          Merge two buffers.

M-x emerge-buffers-with-ancestor
          Merge two buffers with reference to a common ancestor in a third
          buffer.

 The Emerge commands compare two files or buffers, and display the comparison
in three buffers: one for each input text (the A buffer and the B buffer), and
one (the merge buffer) where merging takes place.  The merge buffer shows the
full merged text, not just the differences.  Wherever the two input texts
differ, you can choose which one of them to include in the merge buffer.

 The Emerge commands that take input from existing buffers use only the
accessible portions of those buffers, if they are narrowed (see Narrowing).

 If a common ancestor version is available, from which the two texts to be
merged were both derived, Emerge can use it to guess which alternative is
right.  Wherever one current version agrees with the ancestor, Emerge presumes
that the other current version is a deliberate change which should be kept in
the merged version.  Use the `with-ancestor' commands if you want to specify a
common ancestor text.  These commands read three file or buffer names---variant
A, variant B, and the common ancestor.

 After the comparison is done and the buffers are prepared, the interactive
merging starts.  You control the merging by typing special commands in the
merge buffer.  The merge buffer shows you a full merged text, not just
differences.  For each run of differences between the input texts, you can
choose which one of them to keep, or edit them both together.

 The merge buffer uses a special major mode, Emerge mode, with commands for
making these choices.  But you can also edit the buffer with ordinary Emacs
commands.

 At any given time, the attention of Emerge is focused on one particular
difference, called the selected difference.  This difference is marked off in
the three buffers like this:

vvvvvvvvvvvvvvvvvvvv
text that differs
^^^^^^^^^^^^^^^^^^^^

Emerge numbers all the differences sequentially and the mode line always shows
the number of the selected difference.

 Normally, the merge buffer starts out with the A version of the text. But when
the A version of a part of the buffer agrees with the common ancestor, then the
B version is preferred for that part.

 Emerge leaves the merged text in the merge buffer when you exit.  At that
point, you can save it in a file with C-x C-w.  If you give a prefix argument
to emerge-files or emerge-files-with-ancestor, it reads the name of the output
file using the minibuffer.  (This is the last file name those commands read.)
Then exiting from Emerge saves the merged text in the output file.

 If you abort Emerge with C-], the output is not saved.


ΓòÉΓòÉΓòÉ 25.13.2. Submodes of Emerge ΓòÉΓòÉΓòÉ

 You can choose between two modes for giving merge commands: Fast mode and Edit
mode.  In Fast mode, basic Emerge commands are single characters, but ordinary
Emacs commands are disabled.  This is convenient if you use only Emerge
commands.

 In Edit mode, all Emerge commands start with the prefix key C-c C-c, and the
normal Emacs commands are also available.  This allows editing the merge
buffer, but slows down Emerge operations.

 Use e to switch to Edit mode, and C-c C-c f to switch to Fast mode.  The mode
line indicates Edit and Fast modes with `E' and `F'.

 Emerge has two additional submodes that affect how particular merge commands
work: Auto Advance mode and Skip Prefers mode.

 If Auto Advance mode is in effect, the a and b commands advance to the next
difference.  This lets you go through the merge faster as long as you simply
choose one of the alternatives from the input.  The mode line indicates Auto
Advance mode with `A'.

 If Skip Prefers mode is in effect, the n and p commands skip over differences
in states prefer-A and prefer-B.  Thus you see only differences for which
neither version is presumed ``correct''.  The mode line indicates Skip Prefers
mode with `S'.

 Use the command s a (emerge-auto-advance-mode) to set or clear Auto Advance
mode.  Use s s (emerge-skip-prefers-mode) to set or clear Skip Prefers mode.
These commands turn on the mode with a positive argument, turns it off with a
negative or zero argument, and toggle the mode with no argument.


ΓòÉΓòÉΓòÉ 25.13.3. State of a Difference ΓòÉΓòÉΓòÉ

 In the merge buffer, a difference is marked with lines of `v' and `^'
characters.  Each difference has one of these seven states:

A
          The difference is showing the A version.  The a command always
          produces this state; the mode line indicates it with `A'.

B
          The difference is showing the B version.  The b command always
          produces this state; the mode line indicates it with `B'.

default-A
default-B
          The difference is showing the A or the B state by default, because
          you haven't made a choice.  All differences start in the default-A
          state (and thus the merge buffer is a copy of the A buffer), except
          those for which one alternative is ``preferred'' (see below).

          When you select a difference, its state changes from default-A or
          default-B to plain A or B.  Thus, the selected difference never has
          state default-A or default-B, and these states are never displayed in
          the mode line.

          The command d a chooses default-A as the default state, and d b
          chooses default-B.  This chosen default applies to all differences
          which you haven't selected and for which no alternative is preferred.
          If you are moving through the merge sequentially, the differences you
          haven't selected are those following the selected one.  Thus, while
          moving sequentially, you can effectively make the A version the
          default for some sections of the merge buffer and the B version the
          default for others by using d a and d b at the end of each section.

prefer-A
prefer-B
          The difference is showing the A or B state because it is preferred.
          This means that you haven't made an explicit choice, but one
          alternative seems likely to be right because the other alternative
          agrees with the common ancestor.  Thus, where the A buffer agrees
          with the common ancestor, the B version is preferred, because chances
          are it is the one that was actually changed.

          These two states are displayed in the mode line as `A*' and `B*'.

combined
          The difference is showing a combination of the A and B states, as a
          result of the x c or x C commands.

          Once a difference is in this state, the a and b commands don't do
          anything to it unless you give them a prefix argument.

          The mode line displays this state as `comb'.


ΓòÉΓòÉΓòÉ 25.13.4. Merge Commands ΓòÉΓòÉΓòÉ

 Here are the Merge commands for Fast mode; in Edit mode, precede them with C-c
C-c:

p
          Select the previous difference.

n
          Select the next difference.

a
          Choose the A version of this difference.

b
          Choose the B version of this difference.

j
          Select a particular difference; specify the sequence number of that
          difference as a prefix argument.

.
          Select the difference containing point.  You can use this command in
          the merge buffer or in the A or B buffer.

q
          Quit---finish the merge.

C-]
          Abort---exit merging and do not save the output.

f
          Go into Fast mode.  (In Edit mode, this is actually C-c C-c f.)

e
          Go into Edit mode.

l
          Recenter (like C-l) all three windows.

-
          Specify part of a prefix numeric argument.

digit
          Also specify part of a prefix numeric argument.

d a
          Choose the A version as the default from here down in the merge
          buffer.

d b
          Choose the B version as the default from here down in the merge
          buffer.

c a
          Copy the A version of this difference into the kill ring.

c b
          Copy the B version of this difference into the kill ring.

i a
          Insert the A version of this difference at the point.

i b
          Insert the B version of this difference at the point.

m
          Put the point and mark around the difference region.

^
          Scroll all three windows down (like M-v).

v
          Scroll all three windows up (like C-v).

<
          Scroll all three windows left (like C-x <).

>
          Scroll all three windows right (like C-x >).

|
          Reset horizontal scroll on all three windows.

x 1
          Shrink the merge window to one line.  (Use C-u l to restore it to
          full size.)

x c
          Combine the two versions of this difference.

x f
          Show the files/buffers Emerge is operating on in Help window. (Use
          C-u l to restore windows.)

x j
          Join this difference with the following one. (C-u x j joins this
          difference with the previous one.)

x s
          Split this difference into two differences.  Before you use this
          command, position point in each of the three buffers to the place
          where you want to split the difference.

x t
          Trim identical lines off top and bottom of the difference. Such lines
          occur when the A and B versions are identical but differ from the
          ancestor version.


ΓòÉΓòÉΓòÉ 25.13.5. Exiting Emerge ΓòÉΓòÉΓòÉ

 The q command (emerge-quit) finishes the merge, storing the results into the
output file if you specified one.  It restores the A and B buffers to their
proper contents, or kills them if they were created by Emerge and you haven't
changed them.  It also disables the Emerge commands in the merge buffer, since
executing them later could damage the contents of the various buffers.

 C-] aborts the merge.  This means exiting without writing the output file.  If
you didn't specify an output file, then there is no real difference between
aborting and finishing the merge.

 If Emerge was called from another Lisp program, then its return value is t for
successful completion, or nil if you abort.


ΓòÉΓòÉΓòÉ 25.13.6. Combining the Two Versions ΓòÉΓòÉΓòÉ

 Sometimes you want to keep both alternatives for a particular locus.  To do
this, use x c, which edits the merge buffer like this:

#ifdef NEW
version from A file
#else /* NEW */
version from B file
#endif /* NEW */

While this example shows C preprocessor conditionals delimiting the two
alternative versions, you can specify the strings you want by setting the
variable emerge-combine-versions-template to a string of your choice.  In the
string, `%a' says where to put version A, and `%b' says where to put version B.
The default setting, which produces the results shown above, looks like this:

"#ifdef NEW\n%a#else /* NEW */\n%b#endif /* NEW */\n"


ΓòÉΓòÉΓòÉ 25.13.7. Fine Points of Emerge ΓòÉΓòÉΓòÉ

 During the merge, you mustn't try to edit the A and B buffers yourself. Emerge
modifies them temporarily, but ultimately puts them back the way they were.

 You can have any number of merges going at once---just don't use any one
buffer as input to more than one merge at once, since the temporary changes
made in these buffers would get in each other's way.

 Starting Emerge can take a long time because it needs to compare the files
fully.  Emacs can't do anything else until diff finishes. Perhaps in the future
someone will change Emerge to do the comparison in the background when the
input files are large---then you could keep on doing other things with Emacs
until Emerge gets ready to accept commands.

 After setting up the merge, Emerge runs the hook emerge-startup-hook (see
Hooks).


ΓòÉΓòÉΓòÉ 25.14. C Mode ΓòÉΓòÉΓòÉ

 In addition to the facilities of typical programming language major modes (see
Program Modes), C mode has various special facilities.

M-a
M-e
          In C mode, M-a and M-e now move by complete C statements
          (c-beginning-of-statement and c-end-of-statement).  These commands do
          ordinary, textual sentence motion when in or next to a comment.

M-q
          M-q in C mode runs c-fill-paragraph, which is designed for filling C
          comments.  (We assume you don't want to fill the actual C code in a C
          program.)

C-c C-u
          Move back to the containing preprocessor conditional, setting the
          mark at the starting point (c-up-conditional).

          A prefix argument acts as a repeat count.  With a negative argument,
          this command moves forward to the end of the containing preprocessor
          conditional.  When going backwards, `#elif' acts like `#else'
          followed by `#if'.  When going forwards, `#elif' is ignored.

C-c C-n
          Move forward across the next preprocessor conditional, setting the
          mark at the starting point (c-forward-conditional).

C-c C-p
          Move backward across the previous preprocessor conditional, setting
          the at the starting point (c-backward-conditional).

M-x c-macro-expand
          When you are debugging C code that uses macros, sometimes it is hard
          to figure out precisely how the macros expand.  The command M-x
          c-macro-expand runs the C preprocessor and shows you what expansion
          results from the region.  The portion of the buffer before the region
          is also included in preprocessing, for the sake of macros defined
          there, but the output from this part isn't shown.

M-x c-backslash-region
          Insert or align `\' characters at the ends of the lines of the
          region, except for the last such line.  This is useful after writing
          or editing a C macro definition.

          If a line already ends in `\', this command adjusts the amount of
          whitespace before it.  Otherwise, it inserts a new `\'.

 C++ mode is like C mode, except that it understands C++ comment syntax and
certain other differences between C and C++.  It also has a command M-x
fill-c++-comment, which fills a paragraph made of C++ comment lines.

 The command comment-region is useful in C++ mode for commenting out several
consecutive lines, or removing the commenting out of such lines.  (You don't
need this command with C comment syntax because you don't need to put comment
delimiters on each line.)  See Comments.


ΓòÉΓòÉΓòÉ 25.15. Fortran Mode ΓòÉΓòÉΓòÉ

 Fortran mode provides special motion commands for Fortran statements and
subprograms, and indentation commands that understand Fortran conventions of
nesting, line numbers and continuation statements.  Fortran mode has it's own
Auto Fill mode that breaks long lines into proper Fortran continuation lines.

 Special commands for comments are provided because Fortran comments are unlike
those of other languages.

 Built-in abbrevs optionally save typing when you insert Fortran keywords.

 Use M-x fortran-mode to switch to this major mode.  This command runs the hook
fortran-mode-hook (see Hooks).

 Fortran mode was contributed by Michael Prange.  It has been updated by
Stephen A. Wood who has collated the contributions and suggestions of many
users.


ΓòÉΓòÉΓòÉ 25.15.1. Motion Commands ΓòÉΓòÉΓòÉ

 Fortran mode provides special commands to move by subprograms (functions and
subroutines) and by statements.  There is also a command to put the region
around one subprogram, convenient for killing it or moving it.

C-M-a
          Move to beginning of subprogram (beginning-of-fortran-subprogram).

C-M-e
          Move to end of subprogram (end-of-fortran-subprogram).

C-M-h
          Put point at beginning of subprogram and mark at end
          (mark-fortran-subprogram).

C-c C-n
          Move to beginning of current or next statement
          (fortran-next-statement).

C-c C-p
          Move to beginning of current or previous statement
          (fortran-previous-statement).


ΓòÉΓòÉΓòÉ 25.15.2. Fortran Indentation ΓòÉΓòÉΓòÉ

 Special commands and features are needed for indenting Fortran code in order
to make sure various syntactic entities (line numbers, comment line indicators
and continuation line flags) appear in the columns that are required for
standard Fortran.


ΓòÉΓòÉΓòÉ 25.15.2.1. Fortran Indentation Commands ΓòÉΓòÉΓòÉ

TAB
          Indent the current line (fortran-indent-line).

LFD
          Indent the current and start a new indented line
          (fortran-indent-new-line).

M-LFD
          Break the current line and set up a continuation line.

C-M-q
          Indent all the lines of the subprogram point is in
          (fortran-indent-subprogram).

 Fortran mode redefines TAB to reindent the current line for Fortran
(fortran-indent-line).  This command indents Line numbers and continuation
markers to their required columns, and independently indents the body of the
statement based on its nesting in the program.

 The key LFD runs the command fortran-indent-new-line, which reindents the
current line then makes and indents a new line. This command is useful to
reindent the closing statement of `do' loops and other blocks before starting a
new line.

 The key C-M-q runs fortran-indent-subprogram, a command to reindent all the
lines of the Fortran subprogram (function or subroutine) containing point.

 The key M-LFD runs fortran-split-line, which splits a line in the appropriate
fashion for Fortran.  In a non-comment line, the second half becomes a
continuation line and is indented accordingly.  In a comment line, both halves
become separate comment lines.


ΓòÉΓòÉΓòÉ 25.15.2.2. Continuation Lines ΓòÉΓòÉΓòÉ

 Most modern Fortran compilers allow two ways of writing continuation lines.
If the first non-space character on a line is in column 5, then that line is a
continuation of the previous line.  We call this fixed format.  (In GNU Emacs
we always count columns from 0.)  A line that starts with a tab character
followed by any digit except `0' is also a continuation line.  We call this
style of continuation tab format.

 Fortran mode can make either style of continuation line, but you must specify
which one you prefer.  The value of the variable indent-tabs-mode controls the
choice: nil for fixed format, and non-nil for tab format.  You can tell which
style is presently in effect by the presence or absence of the string `Tab' in
the mode line.

 If the text on a line starts with the conventional Fortran continuation marker
`$', or if it begins with any non-whitespace character in column 5, Fortran
mode treats it as a continuation line. When you indent a continuation line with
TAB, it converts the line to the current continuation style.  When you split a
Fortran statement with M-LFD, the continuation marker on the newline is created
according to the continuation style.

 The setting of continuation style affects several other aspects of editing in
Fortran mode.  In fixed format mode, the minimum column number for the body of
a statement is 6.  Lines inside of Fortran blocks that are indented to larger
column numbers always use only the space character for whitespace.  In tab
format mode, the minimum column number for the statement body is 8, and the
whitespace before column 8 must always consist of one tab character.

 When you enter Fortran mode for an existing file, it tries to deduce the
proper continuation style automatically from the file contents.  The first line
that begins with either a tab character or six spaces determines the choice.
The variable fortran-analyze-depth specifies how many lines to consider (at the
beginning of the file); if none of those lines indicates a style, then the
variable fortran-tab-mode-default specifies the style.  If it is nil, that
specifies fixed format, and non-nil specifies tab format.


ΓòÉΓòÉΓòÉ 25.15.2.3. Line Numbers ΓòÉΓòÉΓòÉ

 If a number is the first non-whitespace in the line, Fortran indentation
assumes it is a line number and moves it to columns 0 through 4.  (Columns
always count from 0 in GNU Emacs.)

 Line numbers of four digits or less are normally indented one space. The
variable fortran-line-number-indent controls this; it specifies the maximum
indentation a line number can have.  Line numbers are indented to right-justify
them to end in column 4 unless that would require more than this maximum
indentation.  The default value of the variable is 1.

 Simply inserting a line number is enough to indent it according to these
rules.  As each digit is inserted, the indentation is recomputed. To turn off
this feature, set the variable fortran-electric-line-number to nil.  Then
inserting line numbers is like inserting anything else.


ΓòÉΓòÉΓòÉ 25.15.2.4. Syntactic Conventions ΓòÉΓòÉΓòÉ

 Fortran mode assumes that you follow certain conventions that simplify the
task of understanding a Fortran program well enough to indent it properly:

o Two nested `do' loops never share a `continue' statement.

o Fortran keywords such as `if', `else', `then', `do' and others are written
  without embedded whitespace or line breaks.

  Fortran compilers generally ignore whitespace outside of string constants,
  but Fortran mode does not recognize these keywords if they are not
  contiguous.  Constructs such as `else if' or `end do' are acceptable, but the
  second word should be on the same line as the first and not on a continuation
  line.

If you fail to follow these conventions, the indentation commands may indent
some lines unaesthetically.  However, a correct Fortran program retains its
meaning when reindented even if the conventions are not followed.


ΓòÉΓòÉΓòÉ 25.15.2.5. Variables for Fortran Indentation ΓòÉΓòÉΓòÉ

 Several additional variables control how Fortran indentation works:

fortran-do-indent
          Extra indentation within each level of `do' statement (default 3).

fortran-if-indent
          Extra indentation within each level of `if' statement (default 3).
          This value is also used for extra indentation within each level of
          the Fortran 90 `where' statement.

fortran-structure-indent
          Extra indentation within each level of `structure', `union', or `map'
          statements (default 3).

fortran-continuation-indent
          Extra indentation for bodies of continuation lines (default 5).

fortran-check-all-num-for-matching-do
          If this is nil, indentation assumes that each `do' statement ends on
          a `continue' statement.  Therefore, when computing indentation for a
          statement other than `continue', it can save time by not checking for
          a `do' statement ending there.  If this is non-nil, indenting any
          numbered statement must check for a `do' that ends there.  The
          default is nil.

fortran-blink-matching-if
          If this is t, indenting an `endif' statement moves the cursor
          momentarily to the matching `if' statement to show where it is.  The
          default is nil.

fortran-minimum-statement-indent-fixed
          Minimum indentation for fortran statements when using fixed format
          continuation line style.  Statement bodies are never indented less
          than this much.  The default is 6.

fortran-minimum-statement-indent-tab
          Minimum indentation for fortran statements for tab format
          continuation line style.  Statement bodies are never indented less
          than this much.  The default is 8.


ΓòÉΓòÉΓòÉ 25.15.3. Comments ΓòÉΓòÉΓòÉ

 The usual Emacs comment commands assume that a comment can follow a line of
code.  In Fortran, the standard comment syntax requires an entire line to be
just a comment.  Therefore, Fortran mode replaces the standard Emacs comment
commands and defines some new variables.

 Fortran mode can also handle a nonstandard comment syntax where comments start
with `!' and can follow other text.  Because only some Fortran compilers accept
this syntax, Fortran mode will not insert such comments unless you have said in
advance to do so.  To do this, set the variable comment-start to `"!"' (see
Variables).

M-;
          Align comment or insert new comment (fortran-comment-indent).

C-x ;
          Applies to nonstandard `!' comments only.

C-c ;
          Turn all lines of the region into comments, or (with argument) turn
          them back into real code (fortran-comment-region).

 M-; in Fortran mode is redefined as the command fortran-comment-indent.  Like
the usual M-; command, this recognizes any kind of existing comment and aligns
its text appropriately; if there is no existing comment, a comment is inserted
and aligned.  But inserting and aligning comments are not the same in Fortran
mode as in other modes.

 When a new comment must be inserted, if the current line is blank, a full-line
comment is inserted.  On a non-blank line, a nonstandard `!' comment is
inserted if you have said you want to use them.  Otherwise a full-line comment
is inserted on a new line before the current line.

 Nonstandard `!' comments are aligned like comments in other languages, but
full-line comments are different.  In a standard full-line comment, the comment
delimiter itself must always appear in column zero. What can be aligned is the
text within the comment.  You can choose from three styles of alignment by
setting the variable fortran-comment-indent-style to one of these values:

fixed
          Align the text at a fixed column, which is the sum of
          fortran-comment-line-extra-indent and the minimum statement
          indentation.  This is the default.

          The minimum statement indentation is
          fortran-minimum-statement-indent-fixed for fixed format continuation
          line style and fortran-minimum-statement-indent-tab for tab format
          style.

relative
          Align the text as if it were a line of code, but with an additional
          fortran-comment-line-extra-indent columns of indentation.

nil
          Don't move text in full-line columns automatically at all.

 In addition, you can specify the character to be used to indent within
full-line comments by setting the variable fortran-comment-indent-char to the
single-character string you want to use.

 Fortran mode introduces two variables comment-line-start and
comment-line-start-skip which play for full-line comments the same roles played
by comment-start and comment-start-skip for ordinary text-following comments.
Normally these are set properly by Fortran mode so you do not need to change
them.

 The normal Emacs comment command C-x ; has not been redefined.  If you use `!'
comments, this command can be used with them.  Otherwise it is useless in
Fortran mode.

 The command C-c ; (fortran-comment-region) turns all the lines of the region
into comments by inserting the string `C$$$' at the front of each one.  With a
numeric argument, it turns the region back into live code by deleting `C$$$'
from the front of each line in it.  The string used for these comments can be
controlled by setting the variable fortran-comment-region.  Note that here we
have an example of a command and a variable with the same name; these two uses
of the name never conflict because in Lisp and in Emacs it is always clear from
the context which one is meant.


ΓòÉΓòÉΓòÉ 25.15.4. Fortran Auto Fill Mode ΓòÉΓòÉΓòÉ

 Fortran Auto Fill mode is a minor mode which automatically splits Fortran
statements as you insert them when they become too wide.  Splitting a statement
involves making continuation lines.  This splitting happens when you type SPC,
RET, or TAB, and also in the Fortran indentation commands.

 M-x fortran-auto-fill-mode turns Fortran Auto Fill mode on if it was off, or
off if it was on.  This command works the same as M-x auto-fill-mode does for
normal Auto Fill mode (see Filling).  A positive numeric argument turns Fortran
Auto Fill mode on, and a negative argument turns it off.  You can see when
Fortran Auto Fill mode is in effect by the presence of the word `Fill' in the
mode line, inside the parentheses.  Fortran Auto Fill mode is a minor mode,
turned on or off for each buffer individually.  See Minor Modes.

  Fortran Auto Fill mode breaks lines at spaces or delimiters when the lines
get longer than the desired width (the value of fill-column). The delimiters
that Fortran Auto Fill mode may break at are `,', `'', `+', `-', `/', `*', `=',
and `)'. The line break comes after the delimiter if the variable
fortran-break-before-delimiters is nil.  Otherwise (and by default), the break
comes before the delimiter.

 By default, Fortran Auto Fill mode is not enabled.  If you want this feature
turned on permanently, add a hook function to fortran-mode-hook to execute
(fortran-auto-fill-mode 1). See Hooks.


ΓòÉΓòÉΓòÉ 25.15.5. Columns ΓòÉΓòÉΓòÉ

C-c C-r
          Display a ``column ruler'' momentarily above the current line
          (fortran-column-ruler).

C-c C-w
          Split the current window horizontally temporarily so that it is 72
          columns wide.  This may help you avoid making lines longer than the
          72 character limit that some fortran compilers impose
          (fortran-window-create-momentarily).

 The command C-c C-r (fortran-column-ruler) shows a column ruler momentarily
above the current line.  The comment ruler is two lines of text that show you
the locations of columns with special significance in Fortran programs.  Square
brackets show the limits of the columns for line numbers, and curly brackets
show the limits of the columns for the statement body.  Column numbers appear
above them.

 Note that the column numbers count from zero, as always in GNU Emacs. As a
result, the numbers may be one less than those you are familiar with; but the
positions they indicate in the line are standard for Fortran.

 The text used to display the column ruler is the value of the variable
fortran-comment-ruler.  By changing this variable, you can change the display.

 For even more help, use C-c C-w (fortran-window-create), a command which
splits the current window horizontally, making a window 72 columns wide.  By
editing in this window you can immediately see when you make a line too wide to
be correct Fortran.


ΓòÉΓòÉΓòÉ 25.15.6. Fortran Keyword Abbrevs ΓòÉΓòÉΓòÉ

 Fortran mode provides many built-in abbrevs for common keywords and
declarations.  These are the same sort of abbrev that you can define yourself.
To use them, you must turn on Abbrev mode.  See Abbrevs.

 The built-in abbrevs are unusual in one way: they all start with a semicolon.
You cannot normally use semicolon in an abbrev, but Fortran mode makes this
possible by changing the syntax of semicolon to ``word constituent.''

 For example, one built-in Fortran abbrev is `;c' for `continue'.  If you
insert `;c' and then insert a punctuation character such as a space or a
newline, the `;c' expands automatically to `continue', provided Abbrev mode is
enabled.

 Type `;?' or `;C-h' to display a list of all the built-in Fortran abbrevs and
what they stand for.


ΓòÉΓòÉΓòÉ 25.16. Asm Mode ΓòÉΓòÉΓòÉ

Asm mode is a major mode for editing files of assembler code.  It defines these
commands:

TAB
          tab-to-tab-stop.

LFD
          Insert a newline and then indent using tab-to-tab-stop.

:
          Insert a colon and then remove the indentation from before the label
          preceding colon.  Then do tab-to-tab-stop.

;
          Insert or align a comment.

 The variable asm-comment-char specifies which character starts comments in
assembler syntax.


ΓòÉΓòÉΓòÉ 26. Compiling and Testing Programs ΓòÉΓòÉΓòÉ

 The previous chapter discusses the Emacs commands that are useful for making
changes in programs.  This chapter deals with commands that assist in the
larger process of developing and maintaining programs.


ΓòÉΓòÉΓòÉ 26.1. Running `make', or Compilers Generally ΓòÉΓòÉΓòÉ

 Emacs can run compilers for noninteractive languages such as C and Fortran as
inferior processes, feeding the error log into an Emacs buffer. It can also
parse the error messages and show you the source lines where compilation errors
occurred.

M-x compile
          Run a compiler asynchronously under Emacs, with error messages to
          `*compilation*' buffer.

M-x grep
          Run grep asynchronously under Emacs, with matching lines listed in
          the buffer named `*grep*'.

M-x kill-compilation
M-x kill-grep
          Kill the running compilation or grep subprocess.

C-x `
          Visit the locus of the next compiler error message or grep match.

 To run make or another compilation command, do M-x compile.  This command
reads a shell command line using the minibuffer, and then executes the command
in an inferior shell, putting output in the buffer named `*compilation*'.  The
current buffer's default directory is used as the working directory for the
execution of the command; normally, therefore, the compilation happens in this
directory.

 When the shell command line is read, the minibuffer appears containing a
default command line, which is the command you used the last time you did M-x
compile.  If you type just RET, the same command line is used again.  For the
first M-x compile, the default is `make -k'.

 The default compilation command comes from the variable compile-command; if
the appropriate compilation command for a file is something other than `make
-k', it can be useful for the file to specify a local value for compile-command
( see File Variables).

 Starting a compilation displays the buffer `*compilation*' in another window
but does not select it.  The buffer's mode line tells you whether compilation
is finished, with the word `run' or `exit' inside the parentheses.  You do not
have to keep this buffer visible; compilation continues in any case.  While a
compilation is going on, the string `Compiling' appears in the mode lines of
all windows.  When this string disappears, the compilation is finished.

 To kill the compilation process, do M-x kill-compilation.  When the compiler
process terminates, the mode line of the `*compilation*' buffer changes to say
`signal' instead of `run'.  Starting a new compilation also kills any running
compilation, as only one can exist at any time.  However, M-x compile asks for
confirmation before actually killing a compilation that is running.

 The `*compilation*' buffer uses a special major mode, Compilation mode.  This
mode provides the keys SPC and DEL to scroll by screenfuls, and M-n and M-p to
move to the next or previous error message.  You can also use M-{ and M-} to
move up or down to an error message for a different source file. You can visit
the source for any particular error message by moving point in `*compilation*'
to that error message and typing C-c C-c (compile-goto-error).

 To parse the compiler error messages sequentially, type C-x ` (next-error).
The character following the C-x is the backquote or ``grave accent,'' not the
single-quote.  This command is available in all buffers, not just in
`*compilation*'.  It displays the next error message at the top of one window
and source location of the error in another window.

 The first time C-x ` is used after the start of a compilation, it moves to the
first error's location.  Subsequent uses of C-x ` advance down the data set up
by the first use.  When the preparsed error messages are exhausted, the next
C-x ` checks for any more error messages that have come in; this is useful if
you start editing the compilation errors while the compilation is still going
on.  If no more error messages have come in, C-x ` reports an error.

 C-u C-x ` discards the preparsed error message data and parses the
`*compilation*' buffer over again, then displaying the first error. This way,
you can process the same set of errors again.

 Instead of running a compiler, you can run grep and see the lines on which
matches were found.  To do this, type M-x grep with an argument line that
contains the same arguments you would give grep when running it normally: a
grep-style regexp (usually in single-quotes to quote the shell's special
characters) followed by file names which may use wildcards. The output from
grep goes in the `*grep*' buffer and the lines that matched can be found with
C-x ` as if they were compilation errors.

 Note: a shell is used to run the compile command, but the shell is told that
it should be noninteractive.  This means in particular that the shell starts up
with no prompt.  If you find your usual shell prompt making an unsightly
appearance in the `*compilation*' buffer, it means you have made a mistake in
your shell's init file (`.cshrc' or `.shrc' or ...) by setting the prompt
unconditionally.  The shell init file should set the prompt only if there
already is a prompt.  In csh, here is how to do it:

if ($?prompt) set prompt = ...


ΓòÉΓòÉΓòÉ 26.2. Running Debuggers Under Emacs ΓòÉΓòÉΓòÉ

The GUD (Grand Unified Debugger) library provides an interface to various
symbolic debuggers from within Emacs.  We recommend the debugger GDB, which is
free software, but you can also run DBX or SDB if you have them.


ΓòÉΓòÉΓòÉ 26.2.1. Starting GUD ΓòÉΓòÉΓòÉ

 There are three commands for starting a debugger, each corresponding to a
particular debugger program.

M-x gdb RET file RET
          Run GDB as a subprocess of Emacs.  This command creates a buffer for
          input and output to GDB, and switches to it.  If a GDB buffer already
          exists, it just switches to that buffer.

M-x dbx RET file RET
          Similar, but run DBX instead of GDB.

M-x sdb RET file RET
          Similar, but run SDB instead of GDB.

           Some versions of SDB do not mention source file names in their
          messages.  When you use them, you need to have a valid tags table
          (see Tags) in order for GUD to find functions in the source code. If
          you have not visited a tags table or the tags table doesn't list one
          of the functions, you get a message saying `The sdb support requires
          a valid tags table to work'.  If this happens, generate a valid tags
          table in the working directory and try again.

M-x xdb
          Similar, but run XDB instead of GDB.

 You can only run one debugger process at a time.

 Each of these commands takes one argument: a command line to invoke the
debugger.  In the simplest case, specify just the name of the executable file
you want to debug.  You may also use options that the debugger supports.
However, shell wild cards and variables are not allowed.  GUD assumes that the
first argument not preceded by a `-' is the executable file name.


ΓòÉΓòÉΓòÉ 26.2.2. Debugger Operation ΓòÉΓòÉΓòÉ

 When you run a debugger with GUD, the debugger uses an Emacs buffer for its
ordinary input and output.  This is called the GUD buffer.  The debugger uses
other Emacs buffers to display the source files of the program.  An arrow
(`=>') in one of these buffers indicates the current execution line.  Moving
point in this buffer does not move the arrow.

 You can start editing these source files at any time in the buffers that were
made to display them.  The arrow is not part of the file's text; it appears
only on the screen.  If you do modify a source file, keep in mind that
inserting or deleting lines will throw off the arrow's positioning; GUD has no
way of figuring out which line corresponded before your changes to the line
number in a debugger message.  Also, you'll typically have to recompile and
restart the program for your changes to be reflected in the debugger's tables.

If you wish, you can control your debugger process entirely through the
debugger buffer, which uses a variant of Shell mode.  All the usual commands
for your debugger are available, and you can use the Shell mode history
commands to repeat them.


ΓòÉΓòÉΓòÉ 26.2.3. Commands of GUD ΓòÉΓòÉΓòÉ

 GUD provides a command available in all buffers for setting breakpoints.  This
command is defined globally because you need to use it in the source files'
buffers.

C-x SPC
          Set a breakpoint on the line that point is on.

 Here are the other commands provided by GUD.  The keys starting with C-c are
available only in the GUD interaction buffer.  The bindings that start with C-x
C-a are available in the GUD buffer and also in source files.

C-c C-l
C-x C-a C-l
          Display in another window the last line referred to in the GUD buffer
          (that is, the line indicated in the last location message). This runs
          the command gud-refresh.

C-c C-s
C-x C-a C-s
          Execute a single line of code (gud-step).  If the code contains a
          function call, execution stops after entering the called function.

C-c C-n
C-x C-a C-n
          Execute a single line of code, stepping across entire function calls
          at full speed (gud-next).

C-c C-i
C-x C-a C-i
          Execute a single machine instruction (gud-stepi).

C-c C-c
C-x C-a C-c
          Continue execution until the next breakpoint, or other event that
          would normally stop the program (gud-cont).

C-c C-d
C-x C-a C-d
          Delete the breakpoint(s) on the current source line, if any
          (gud-remove).  If you use this command in the GUD interaction buffer,
          it applies to the line where the program last stopped.

C-c C-t
C-x C-a C-t
          Set a temporary breakpoint on the current source line, if any. If you
          use this command in the GUD interaction buffer, it applies to the
          line where the program last stopped.

 The above commands are common to all supported debuggers.  If you are using
GDB or (some versions of) DBX, these additional commands are available:

C-c <
C-x C-a <
          Select the next enclosing stack frame (gud-up).  This is equivalent
          to the `up' command.

C-c >
C-x C-a >
          Select the next inner stack frame (gud-down).  This is equivalent to
          the `down' command.

 If you are using GDB, two additional keybindings are available:

C-c C-f
C-x C-a C-f
          Run the program until the selected stack frame returns (or until it
          stops for some other reason).

 These commands interpret a prefix argument as a repeat count, when that makes
sense.


ΓòÉΓòÉΓòÉ 26.2.4. GUD Customization ΓòÉΓòÉΓòÉ

 On startup, GUD runs one of the following hooks: gdb-mode-hook, if you are
using GDB; dbx-mode-hook, if you are using DBX; sdb-mode-hook, if you are using
SDB; and xdb-mode-hook, if you are using XDB.  You can use these hooks to
define custom keybindings for the debugger interaction buffer.  See Hooks.

 Here is a convenient way to define a command that sends a particular command
string to the debugger, and set up a key binding for it in the debugger
interaction buffer:

(gud-def function cmdstring binding docstring)

 This defines a command named function which sends cmdstring to the debugger
process, with documentation string docstring.  You can use the command thus
defined in any buffer. If binding is non-nil, gud-def also binds the command to
C-c binding in the GUD buffer's mode and to C-x C-a binding generally.

 The command string cmdstring may contain certain escape sequences that are
filled in with varying data at the time function is called:

`%f'
          Name of the current source file.  If the current buffer is the GUD
          buffer, then the ``current source file'' is the file that the program
          stopped in.

`%l'
          Number of the current source line.  If the current buffer is the GUD
          buffer, then the ``current source line'' is the line that the program
          stopped in.

`%e'
          Text of the C lvalue or function-call expression surrounding point.

`%a'
          Text of the hexadecimal address surrounding point.

`%p'
          Prefix (numeric) argument of the called function (if any) as a
          number. (If you don't use `%p' in the command string, the command you
          define ignores any prefix argument.)


ΓòÉΓòÉΓòÉ 26.3. Executing Lisp Expressions ΓòÉΓòÉΓòÉ

 Emacs has several different major modes for Lisp and Scheme.  They are the
same in terms of editing commands, but differ in the commands for executing
Lisp expressions.

Emacs-Lisp mode
          The mode for editing source files of programs to run in Emacs Lisp.
          This mode defines C-M-x to evaluate the current defun. See Lisp
          Libraries.

Lisp Interaction mode
          The mode for an interactive session with Emacs Lisp.  It defines LFD
          to evaluate the sexp before point and insert its value in the buffer.
          See Lisp Interaction.

Lisp mode
          The mode for editing source files of programs that run in Lisps other
          than Emacs Lisp.  This mode defines C-M-x to send the current defun
          to an inferior Lisp process.  See External Lisp.

Inferior Lisp mode
          The mode for an interactive session with an inferior Lisp process.
          This mode combines the special features of Lisp mode and Shell mode
          (see Shell Mode).

Scheme mode
          Like Lisp mode but for Scheme programs.

Inferior Scheme mode
          The mode for an interactive session with an inferior Scheme process.


ΓòÉΓòÉΓòÉ 26.4. Libraries of Lisp Code for Emacs ΓòÉΓòÉΓòÉ

 Lisp code for Emacs editing commands is stored in files whose names
conventionally end in `.el'.  This ending tells Emacs to edit them in
Emacs-Lisp mode (see Executing Lisp).

 To execute a file of Emacs Lisp code, use M-x load-file.  This command reads a
file name using the minibuffer and then executes the contents of that file as
Lisp code.  It is not necessary to visit the file first; in any case, this
command reads the file as found on disk, not text in an Emacs buffer.

 Once a file of Lisp code is installed in the Emacs Lisp library directories,
users can load it using M-x load-library.  Programs can load it by calling
load-library, or with load, a more primitive function that is similar but
accepts some additional arguments.

 M-x load-library differs from M-x load-file in that it searches a sequence of
directories and tries three file names in each directory.  Suppose your
argument is lib; the three names are `lib.elc', `lib.el', and lastly just
`lib'.  If `lib.elc' exists, it is by convention the result of compiling
`lib.el'; it is better to load the compiled file, since it will load and run
faster.

 If load-library finds that `lib.el' is newer than `lib.elc' file, it prints a
warning, because it's likely that somebody made changes to the `.el' file and
forgot to recompile it.

 Because the argument to load-library is usually not in itself a valid file
name, file name completion is not available.  Indeed, when using this command,
you usually do not know exactly what file name will be used.

 The sequence of directories searched by M-x load-library is specified by the
variable load-path, a list of strings that are directory names.  The default
value of the list contains the directory where the Lisp code for Emacs itself
is stored.  If you have libraries of your own, put them in a single directory
and add that directory to load-path.  nil in this list stands for the current
default directory, but it is probably not a good idea to put nil in the list.
If you find yourself wishing that nil were in the list, most likely what you
really want to do is use M-x load-file this once.

 Often you do not have to give any command to load a library, because the
commands defined in the library are set up to autoload that library. Running
any of those commands causes load to be called to load the library; this
replaces the autoload definitions with the real ones from the library.

 If autoloading a file does not finish, either because of an error or because
of a C-g quit, all function definitions made by the file are undone
automatically.  So are any calls to provide.  As a consequence, if you use one
of the autoloadable commands again, the entire file will be loaded a second
time.  This prevents problems where the command is no longer autoloading but it
works wrong because not all the file was loaded. Function definitions are
undone only for autoloading; explicit calls to load do not undo anything if
loading is not completed.

 Emacs Lisp code can be compiled into byte-code which loads faster, takes up
less space when loaded, and executes faster. See Byte Compilation.

 By convention, the compiled code for a library goes in a separate file whose
name consists of the library source file with `c' appended. Thus, the compiled
code for `foo.el' goes in `foo.elc'. That's why load-library searches for
`.elc' files first.


ΓòÉΓòÉΓòÉ 26.5. Evaluating Emacs-Lisp Expressions ΓòÉΓòÉΓòÉ

 Lisp programs intended to be run in Emacs should be edited in Emacs-Lisp mode;
this happens automatically for file names ending in `.el'.  By contrast, Lisp
mode itself is used for editing Lisp programs intended for other Lisp systems.
To switch to Emacs-Lisp mode explicitly, use the command M-x emacs-lisp-mode.

 For testing of Lisp programs to run in Emacs, it is often useful to evaluate
part of the program as it is found in the Emacs buffer.  For example, after
changing the text of a Lisp function definition, evaluating the definition
installs the change for future calls to the function.  Evaluation of Lisp
expressions is also useful in any kind of editing, for invoking noninteractive
functions (functions that are not commands).

M-ESC
          Read a single Lisp expression in the minibuffer, evaluate it, and
          print the value in the echo area (eval-expression).

C-x C-e
          Evaluate the Lisp expression before point, and print the value in the
          echo area (eval-last-sexp).

C-M-x
          Evaluate the defun containing or after point, and print the value in
          the echo area (eval-defun).

M-x eval-region
          Evaluate all the Lisp expressions in the region.

M-x eval-current-buffer
          Evaluate all the Lisp expressions in the buffer.

 M-ESC (eval-expression) is the most basic command for evaluating a Lisp
expression interactively.  It reads the expression using the minibuffer, so you
can execute any expression on a buffer regardless of what the buffer contains.
When the expression is evaluated, the current buffer is once again the buffer
that was current when M-ESC was typed.

 M-ESC can easily confuse users who do not understand it, especially on
keyboards with autorepeat where it can result from holding down the ESC key for
too long.  Therefore, eval-expression is normally a disabled command.
Attempting to use this command asks for confirmation and gives you the option
of enabling it; once you enable the command, confirmation will no longer be
required for it. See Disabling.

 In Emacs-Lisp mode, the key C-M-x is bound to the command eval-defun, which
parses the defun containing or following point as a Lisp expression and
evaluates it.  The value is printed in the echo area.  This command is
convenient for installing in the Lisp environment changes that you have just
made in the text of a function definition.

 The command C-x C-e (eval-last-sexp) performs a similar job but is available
in all major modes, not just Emacs-Lisp mode.  It finds the sexp before point,
reads it as a Lisp expression, evaluates it, and prints the value in the echo
area.  It is sometimes useful to type in an expression and then, with point
still after it, type C-x C-e.

 If C-M-x or C-x C-e is given a numeric argument, it prints the value by
insertion into the current buffer at point, rather than in the echo area.  The
argument value does not matter.

 The most general command for evaluating Lisp expressions from a buffer is
eval-region.  M-x eval-region parses the text of the region as one or more Lisp
expressions, evaluating them one by one. M-x eval-current-buffer is similar but
evaluates the entire buffer.  This is a reasonable way to install the contents
of a file of Lisp code that you are just ready to test.  After finding and
fixing a bug, use C-M-x on each function that you change, to keep the Lisp
world in step with the source file.


ΓòÉΓòÉΓòÉ 26.6. Lisp Interaction Buffers ΓòÉΓòÉΓòÉ

 The buffer `*scratch*' which is selected when Emacs starts up is provided for
evaluating Lisp expressions interactively inside Emacs.

 Thus, the way to use the `*scratch*' buffer is to insert Lisp expressions at
the end, ending each one with LFD so that it will be evaluated.  This command
reads the Lisp expression before point, evaluates it, and inserts the value in
printed representation before point.  The result is a complete typescript of
the expressions you have evaluated and their values.

 The `*scratch*' buffer's major mode is Lisp Interaction mode, which is the
same as Emacs-Lisp mode except for the binding of LFD.

 The rationale for this feature is that Emacs must have a buffer when it starts
up, but that buffer is not useful for editing files since a new buffer is made
for every file that you visit.  The Lisp interpreter typescript is the most
useful thing I can think of for the initial buffer to do.  Type M-x
lisp-interaction-mode to put the current buffer in Lisp Interaction mode.


ΓòÉΓòÉΓòÉ 26.7. Running an External Lisp ΓòÉΓòÉΓòÉ

 Emacs has facilities for running programs in other Lisp systems.  You can run
a Lisp process as an inferior of Emacs, and pass expressions to it to be
evaluated.  You can also pass changed function definitions directly from the
Emacs buffers in which you edit the Lisp programs to the inferior Lisp process.

 To run an inferior Lisp process, type M-x run-lisp.  This runs the program
named lisp, the same program you would run by typing lisp as a shell command,
with both input and output going through an Emacs buffer named `*lisp*'.  That
is to say, any ``terminal output'' from Lisp will go into the buffer, advancing
point, and any ``terminal input'' for Lisp comes from text in the buffer.  (You
can change the name of the Lisp executable file by setting the variable
inferior-lisp-program.)

 To give input to Lisp, go to the end of the buffer and type the input,
terminated by RET.  The `*lisp*' buffer is in Inferior Lisp mode, which
combines the special characteristics of Lisp mode and Shell mode (see Shell
Mode).

 For the source files of programs to run in external Lisps, use Lisp mode. This
mode can be selected with M-x lisp-mode, and is used automatically for files
whose names end in `.l' or `.lisp', as most Lisp systems usually expect.

 When you edit a function in a Lisp program you are running, the easiest way to
send the changed definition to the inferior Lisp process is the key C-M-x.  In
Lisp mode, this runs the function lisp-send-defun, which finds the defun around
or following point and sends it as input to the Lisp process.  (Emacs can send
input to any inferior process regardless of what buffer is current.)

 Contrast the meanings of C-M-x in Lisp mode (for editing programs to be run in
another Lisp system) and Emacs-Lisp mode (for editing Lisp programs to be run
in Emacs): in both modes it has the effect of installing the function
definition that point is in, but the way of doing so is different according to
where the relevant Lisp environment is found. See Executing Lisp.


ΓòÉΓòÉΓòÉ 27. Abbrevs ΓòÉΓòÉΓòÉ

 An abbrev is a word which expands, if you insert it, into some different text.
Abbrevs are defined by the user to expand in specific ways.  For example, you
might define `foo' as an abbrev expanding to `find outer otter'.  With this
abbrev defined, you would be able to get `find outer otter ' into the buffer by
typing f o o SPC.

 Abbrevs expand only when Abbrev mode (a minor mode) is enabled. Disabling
Abbrev mode does not cause abbrev definitions to be forgotten, but they do not
expand until Abbrev mode is enabled again.  The command M-x abbrev-mode toggles
Abbrev mode; with a numeric argument, it turns Abbrev mode on if the argument
is positive, off otherwise. See Minor Modes.  abbrev-mode is also a variable;
Abbrev mode is on when the variable is non-nil.  The variable abbrev-mode
automatically becomes local to the current buffer when it is set.

 Abbrev definitions can be mode-specific---active only in one major mode.
Abbrevs can also have global definitions that are active in all major modes.
The same abbrev can have a global definition and various mode-specific
definitions for different major modes.  A mode specific definition for the
current major mode overrides a global definition.

 Abbrevs can be defined interactively during the editing session.  Lists of
abbrev definitions can also be saved in files and reloaded in later sessions.
Some users keep extensive lists of abbrevs that they load in every session.

 A second kind of abbreviation facility is called the dynamic expansion.
Dynamic abbrev expansion happens only when you give an explicit command and the
result of the expansion depends only on the current contents of the buffer.
See Dynamic Abbrevs.


ΓòÉΓòÉΓòÉ 27.1. Defining Abbrevs ΓòÉΓòÉΓòÉ

C-x a g
          Define an abbrev, using one or more words before point as its
          expansion (add-global-abbrev).

C-x a l
          Similar, but define an abbrev specific to the current major mode
          (add-mode-abbrev).

C-x a i g
          Define a word in the buffer as an abbrev (inverse-add-global-abbrev).

C-x a i l
          Define a word in the buffer as a mode-specific abbrev
          (inverse-add-mode-abbrev).

M-x kill-all-abbrevs
          After this command, there are no abbrev definitions in effect.

 The usual way to define an abbrev is to enter the text you want the abbrev to
expand to, position point after it, and type C-x a g (add-global-abbrev).  This
reads the abbrev itself using the minibuffer, and then defines it as an abbrev
for one or more words before point.  Use a numeric argument to say how many
words before point should be taken as the expansion.  For example, to define
the abbrev `foo' as mentioned above, insert the text `find outer otter' and
then type C-u 3 C-x a g f o o RET.

 An argument of zero to C-x a g means to use the contents of the region as the
expansion of the abbrev being defined.

 The command C-x a l (add-mode-abbrev) is similar, but defines a mode-specific
abbrev.  Mode specific abbrevs are active only in a particular major mode.  C-x
a l defines an abbrev for the major mode in effect at the time C-x a l is
typed.  The arguments work the same as for C-x a g.

 If the text of the abbrev you want is already in the buffer instead of the
expansion, use command C-x a i g (inverse-add-global-abbrev) instead of C-x a
g, or use C-x a i l (inverse-add-mode-abbrev) instead of C-x a l.  These
commands are called ``inverse'' because they invert the meaning of the argument
found in the buffer and the argument read using the minibuffer.

 To change the definition of an abbrev, just add the new definition. You will
be asked to confirm if the abbrev has a prior definition.  To remove an abbrev
definition, give a negative argument to C-x a g or C-x a l.  You must choose
the command to specify whether to kill a global definition or a mode-specific
definition for the current mode, since those two definitions are independent
for one abbrev.

 M-x kill-all-abbrevs removes all the abbrev definitions there are.


ΓòÉΓòÉΓòÉ 27.2. Controlling Abbrev Expansion ΓòÉΓòÉΓòÉ

 An abbrev expands whenever it is present in the buffer just before point and a
self-inserting punctuation character (SPC, comma, etc.) is typed.  Most often
the way an abbrev is used is to insert the abbrev followed by punctuation.

 Abbrev expansion preserves case; thus, `foo' expands into `find outer otter';
`Foo' into `Find outer otter', and `FOO' into `FIND OUTER OTTER' or `Find Outer
Otter' according to the variable abbrev-all-caps (a non-nil value chooses the
first of the two expansions).

 These two commands are used to control abbrev expansion:

M-'
          Separate a prefix from a following abbrev to be expanded
          (abbrev-prefix-mark).

C-x a e
          Expand the abbrev before point (expand-abbrev). This is effective
          even when Abbrev mode is not enabled.

M-x unexpand-abbrev
          Undo last abbrev expansion.

M-x expand-region-abbrevs
          Expand some or all abbrevs found in the region.

 You may wish to expand an abbrev with a prefix attached; for example, if
`cnst' expands into `construction', you might want to use it to enter
`reconstruction'.  It does not work to type recnst, because that is not
necessarily a defined abbrev.  What does work is to use the command M-'
(abbrev-prefix-mark) in between the prefix `re' and the abbrev `cnst'.  First,
insert `re'.  Then type M-'; this inserts a minus sign in the buffer to
indicate that it has done its work.  Then insert the abbrev `cnst'; the buffer
now contains `re-cnst'.  Now insert a punctuation character to expand the
abbrev `cnst' into `construction'.  The minus sign is deleted at this point,
because M-' left word for this to be done.  The resulting text is the desired
`reconstruction'.

 If you actually want the text of the abbrev in the buffer, rather than its
expansion, you can accomplish this by inserting the following punctuation with
C-q.  Thus, foo C-q - leaves `foo-' in the buffer.

 If you expand an abbrev by mistake, you can undo the expansion (replace the
expansion by the original abbrev text) with M-x unexpand-abbrev.  C-_ (undo)
can also be used to undo the expansion; but first it undoes the insertion of
the following punctuation character.  Therefore, if you want both the
punctuation character and the unexpanded abbrev, you must reinsert the
punctuation character, quoting it with C-q.

 M-x expand-region-abbrevs searches through the region for defined abbrevs, and
for each one found offers to replace it with its expansion. This command is
useful if you have typed in text using abbrevs but forgot to turn on Abbrev
mode first.  It may also be useful together with a special set of abbrev
definitions for making several global replacements at once.  This command is
effective even if Abbrev mode is not enabled.

 Expanding an abbrev runs the hook pre-abbrev-expand-hook (see Hooks).


ΓòÉΓòÉΓòÉ 27.3. Examining and Editing Abbrevs ΓòÉΓòÉΓòÉ

M-x list-abbrevs
          Print a list of all abbrev definitions.

M-x edit-abbrevs
          Edit a list of abbrevs; you can add, alter or remove definitions.

 The output from M-x list-abbrevs looks like this:

(lisp-mode-abbrev-table)
"dk"           0    "define-key"
(global-abbrev-table)
"dfn"          0    "definition"

(Some blank lines of no semantic significance, and some other abbrev tables,
have been omitted.)

 A line containing a name in parentheses is the header for abbrevs in a
particular abbrev table; global-abbrev-table contains all the global abbrevs,
and the other abbrev tables that are named after major modes contain the
mode-specific abbrevs.

 Within each abbrev table, each nonblank line defines one abbrev.  The word at
the beginning is the abbrev.  The number that appears is the number of times
the abbrev has been expanded.  Emacs keeps track of this to help you see which
abbrevs you actually use, in case you decide to eliminate those that you don't
use often.  The string at the end of the line is the expansion.

 M-x edit-abbrevs allows you to add, change or kill abbrev definitions by
editing a list of them in an Emacs buffer.  The list has the same format
described above.  The buffer of abbrevs is called `*Abbrevs*', and is in
Edit-Abbrevs mode.  This mode redefines the key C-c C-c to install the abbrev
definitions as specified in the buffer.  The command that does this is
edit-abbrevs-redefine.  Any abbrevs not described in the buffer are eliminated
when this is done.

 The command edit-abbrevs is actually the same as list-abbrevs except that it
selects the buffer `*Abbrevs*' whereas list-abbrevs merely displays it in
another window.


ΓòÉΓòÉΓòÉ 27.4. Saving Abbrevs ΓòÉΓòÉΓòÉ

 These commands allow you to keep abbrev definitions between editing sessions.

M-x write-abbrev-file
          Write a file describing all defined abbrevs.

M-x read-abbrev-file
          Read such a file and define abbrevs as specified there.

M-x quietly-read-abbrev-file
          Similar but do not display a message about what is going on.

M-x define-abbrevs
          Define abbrevs from definitions in current buffer.

M-x insert-abbrevs
          Insert all abbrevs and their expansions into current buffer.

 M-x write-abbrev-file reads a file name using the minibuffer and writes a
description of all current abbrev definitions into that file.  The text stored
in the file looks like the output of M-x list-abbrevs. This is used to save
abbrev definitions for use in a later session.

 M-x read-abbrev-file reads a file name using the minibuffer and reads the
file, defining abbrevs according to the contents of the file. M-x
quietly-read-abbrev-file is the same except that it does not display a message
in the echo area saying that it is doing its work; it is actually useful
primarily in the `.emacs' file.  If an empty argument is given to either of
these functions, the file name used is the value of the variable
abbrev-file-name, which is by default "~/.abbrev_defs".

 Emacs will offer to save abbrevs automatically if you have changed any of
them, whenever it offers to save all files (for C-x s or C-x C-c).  This
feature can be inhibited by setting the variable save-abbrevs to nil.

 The commands M-x insert-abbrevs and M-x define-abbrevs are similar to the
previous commands but work on text in an Emacs buffer. M-x insert-abbrevs
inserts text into the current buffer before point, describing all current
abbrev definitions; M-x define-abbrevs parses the entire current buffer and
defines abbrevs accordingly.


ΓòÉΓòÉΓòÉ 27.5. Dynamic Abbrev Expansion ΓòÉΓòÉΓòÉ

 The abbrev facility described above operates automatically as you insert text,
but all abbrevs must be defined explicitly.  By contrast, dynamic abbrevs allow
the meanings of abbrevs to be determined automatically from the contents of the
buffer, but dynamic abbrev expansion happens only when you request it
explicitly.

M-/
          Expand the word in the buffer before point as a dynamic abbrev, by
          searching in the buffer for words starting with that abbreviation
          (dabbrev-expand).

 For example, if the buffer contains `does this follow ' and you type f o M-/,
the effect is to insert `follow' because that is the last word in the buffer
that starts with `fo'.  A numeric argument to M-/ says to take the second,
third, etc. distinct expansion found looking backward from point.  Repeating
M-/ searches for an alternative expansion by looking farther back.  After the
entire buffer before point has been considered, the buffer after point is
searched.

 Dynamic abbrev expansion is completely independent of Abbrev mode; the
expansion of a word with M-/ is completely independent of whether it has a
definition as an ordinary abbrev.


ΓòÉΓòÉΓòÉ 28. Editing Pictures ΓòÉΓòÉΓòÉ

 If you want to create a picture made out of text characters (for example, a
picture of the division of a register into fields, as a comment in a program),
use the command M-x edit-picture to enter Picture mode.

 In Picture mode, editing is based on the quarter-plane model of text,
according to which the text characters lie studded on an area that stretches
infinitely far to the right and downward.  The concept of the end of a line
does not exist in this model; the most you can say is where the last nonblank
character on the line is found.

 Of course, Emacs really always considers text as a sequence of characters, and
lines really do have ends.  But in Picture mode most frequently-used keys are
rebound to commands that simulate the quarter-plane model of text.  They do
this by inserting spaces or by converting tabs to spaces.

 Most of the basic editing commands of Emacs are redefined by Picture mode to
do essentially the same thing but in a quarter-plane way.  In addition, Picture
mode defines various keys starting with the C-c prefix to run special picture
editing commands.

 One of these keys, C-c C-c, is pretty important.  Often a picture is part of a
larger file that is usually edited in some other major mode.  M-x edit-picture
records the name of the previous major mode so you can use the C-c C-c command
(picture-mode-exit) later to go back to that mode.  C-c C-c also deletes spaces
from the ends of lines, unless given a numeric argument.

 The commands used in Picture mode all work in other modes (provided the
`picture' library is loaded), but are not bound to keys except in Picture mode.
Note that the descriptions below talk of moving ``one column'' and so on, but
all the picture mode commands handle numeric arguments as their normal
equivalents do.

 Turning on Picture mode runs the hook picture-mode-hook (see Hooks).


ΓòÉΓòÉΓòÉ 28.1. Basic Editing in Picture Mode ΓòÉΓòÉΓòÉ

 Most keys do the same thing in Picture mode that they usually do, but do it in
a quarter-plane style.  For example, C-f is rebound to run
picture-forward-column, a command which moves point one column to the right,
inserting a space if necessary so that the actual end of the line makes no
difference.  C-b is rebound to run picture-backward-column, which always moves
point left one column, converting a tab to multiple spaces if necessary.  C-n
and C-p are rebound to run picture-move-down and picture-move-up, which can
either insert spaces or convert tabs as necessary to make sure that point stays
in exactly the same column. C-e runs picture-end-of-line, which moves to after
the last nonblank character on the line.  There is no need to change C-a, as
the choice of screen model does not affect beginnings of lines.

 Insertion of text is adapted to the quarter-plane screen model through the use
of Overwrite mode (see Minor Modes).  Self-inserting characters replace
existing text, column by column, rather than pushing existing text to the
right.  RET runs picture-newline, which just moves to the beginning of the
following line so that new text will replace that line.

 Picture mode provides erasure instead of deletion and killing of text.  DEL
(picture-backward-clear-column) replaces the preceding character with a space
rather than removing it; this moves point backwards.  C-d
(picture-clear-column) replaces the next character or characters with spaces,
but does not move point.  (If you want to clear characters to spaces and move
forward over them, use SPC.)  C-k (picture-clear-line) really kills the
contents of lines, but does not delete the newlines from the buffer.

 To do actual insertion, you must use special commands.  C-o
(picture-open-line) still creates a blank line, but does so after the current
line; it never splits a line.  C-M-o, split-line, makes sense in Picture mode,
so it is not changed.  LFD (picture-duplicate-line) inserts below the current
line another line with the same contents.

 If you want to do real deletion in Picture mode, use C-w, C-c C-d (which is
defined as delete-char, as C-d is in other modes), or one of the picture
rectangle commands (see Rectangles in Picture).


ΓòÉΓòÉΓòÉ 28.2. Controlling Motion after Insert ΓòÉΓòÉΓòÉ

 Since ``self-inserting'' characters in Picture mode just overwrite and move
point, there is no essential restriction on how point should be moved. Normally
point moves right, but you can specify any of the eight orthogonal or diagonal
directions for motion after a ``self-inserting'' character. This is useful for
drawing lines in the buffer.

C-c <
          Move left after insertion (picture-movement-left).

C-c >
          Move right after insertion (picture-movement-right).

C-c ^
          Move up after insertion (picture-movement-up).

C-c .
          Move down after insertion (picture-movement-down).

C-c `
          Move up and left (``northwest'') after insertion
          (picture-movement-nw).

C-c '
          Move up and right (``northeast'') after insertion
          (picture-movement-ne).

C-c /
          Move down and left (``southwest'') after insertion
          (picture-movement-sw).

C-c \
          Move down and right (``southeast'') after insertion
          (picture-movement-se).

 Two motion commands move based on the current Picture insertion direction.
The command C-c C-f (picture-motion) moves in the same direction as motion
after ``insertion'' currently does, while C-c C-b (picture-motion-reverse)
moves in the opposite direction.


ΓòÉΓòÉΓòÉ 28.3. Picture Mode Tabs ΓòÉΓòÉΓòÉ

 Two kinds of tab-like action are provided in Picture mode.  Use M-TAB
(picture-tab-search) for context-based tabbing.  With no argument, it moves to
a point underneath the next ``interesting'' character that follows whitespace
in the previous nonblank line.  ``Next'' here means ``appearing at a horizontal
position greater than the one point starts out at''.  With an argument, as in
C-u M-TAB, this command moves to the next such interesting character in the
current line.  M-TAB does not change the text; it only moves point.
``Interesting'' characters are defined by the variable picture-tab-chars, which
contains a string whose characters are all considered interesting.  Its default
value is "!-~".

 TAB itself runs picture-tab, which operates based on the current tab stop
settings; it is the Picture mode equivalent of tab-to-tab-stop.  Normally it
just moves point, but with a numeric argument it clears the text that it moves
over.

 The context-based and tab-stop-based forms of tabbing are brought together by
the command C-c TAB, picture-set-tab-stops. This command sets the tab stops to
the positions which M-TAB would consider significant in the current line.  The
use of this command, together with TAB, can get the effect of context-based
tabbing.  But M-TAB is more convenient in the cases where it is sufficient.


ΓòÉΓòÉΓòÉ 28.4. Picture Mode Rectangle Commands ΓòÉΓòÉΓòÉ

 Picture mode defines commands for working on rectangular pieces of the text in
ways that fit with the quarter-plane model.  The standard rectangle commands
may also be useful (see Rectangles).

C-c C-k
          Clear out the region-rectangle (picture-clear-rectangle).  With
          argument, kill it.

C-c C-w r
          Similar but save rectangle contents in register r first
          (picture-clear-rectangle-to-register).

C-c C-y
          Copy last killed rectangle into the buffer by overwriting, with upper
          left corner at point (picture-yank-rectangle).  With argument, insert
          instead.

C-c C-x r
          Similar, but use the rectangle in register r
          (picture-yank-rectangle-from-register).

 The picture rectangle commands C-c C-k (picture-clear-rectangle) and C-c C-w
(picture-clear-rectangle-to-register) differ from the standard rectangle
commands in that they normally clear the rectangle instead of deleting it; this
is analogous with the way C-d is changed in Picture mode.

 However, deletion of rectangles can be useful in Picture mode, so these
commands delete the rectangle if given a numeric argument.

 The Picture mode commands for yanking rectangles differ from the standard ones
in overwriting instead of inserting.  This is the same way that Picture mode
insertion of other text differs from other modes. C-c C-y
(picture-yank-rectangle) inserts (by overwriting) the rectangle that was most
recently killed, while C-c C-x (picture-yank-rectangle-from-register) does
likewise for the rectangle found in a specified register.


ΓòÉΓòÉΓòÉ 29. Sending Mail ΓòÉΓòÉΓòÉ

 To send a message in Emacs, you start by typing a command (C-x m) to select
and initialize the `*mail*' buffer.  Then you edit the text and headers of the
message in this buffer, and type another command (C-c C-c) to send the message.

C-x m
          Begin composing a message to send (mail).

C-x 4 m
          Likewise, but display the message in another window
          (mail-other-window).

C-x 5 m
          Likewise, but make a new frame (mail-other-frame).

C-c C-c
          In Mail mode, send the message and switch to another buffer
          (mail-send-and-exit).

 The command C-x m (mail) selects a buffer named `*mail*' and initializes it
with the skeleton of an outgoing message.  C-x 4 m (mail-other-window) selects
the `*mail*' buffer in a different window, leaving the previous current buffer
visible.  C-x 5 m (mail-other-frame) creates a new frame to select the `*mail*'
buffer.

 Because the mail composition buffer is an ordinary Emacs buffer, you can
switch to other buffers while in the middle of composing mail, and switch back
later (or never).  If you use the C-x m command again when you have been
composing another message but have not sent it, you are asked to confirm before
the old message is erased.  If you answer n, the `*mail*' buffer is left
selected with its old contents, so you can finish the old message and send it.
C-u C-x m is another way to do this.  Sending the message marks the `*mail*'
buffer ``unmodified'', which avoids the need for confirmation when C-x m is
next used.

 If you are composing a message in the `*mail*' buffer and want to send another
message before finishing the first, rename the `*mail*' buffer using M-x
rename-uniquely ( see Misc Buffer).  Then you can use C-x m or its variants
described above to make a new `*mail' buffer.  Once you've done that, you can
work with each mail buffer independently.


ΓòÉΓòÉΓòÉ 29.1. The Format of the Mail Buffer ΓòÉΓòÉΓòÉ

 In addition to the text or body, a message has header fields which say who
sent it, when, to whom, why, and so on.  Some header fields such as the date
and sender are created automatically after the message is sent.  Others, such
as the recipient names, must be specified by you in order to send the message
properly.

 Mail mode provides a few commands to help you edit some header fields, and
some are preinitialized in the buffer automatically at times.  You can insert
or edit any header fields using ordinary editing commands.

 The line in the buffer that says

--text follows this line--

is a special delimiter that separates the headers you have specified from the
text.  Whatever follows this line is the text of the message; the headers
precede it.  The delimiter line itself does not appear in the message actually
sent.  The text used for the delimiter line is controlled by the variable
mail-header-separator.

Here is an example of what the headers and text in the `*mail*' buffer might
look like.

To: [e-mail]
CC: [e-mail], [e-mail]
Subject: The Emacs Manual
--Text follows this line--
Please ignore this message.


ΓòÉΓòÉΓòÉ 29.2. Mail Header Fields ΓòÉΓòÉΓòÉ

 There are several header fields you can use in the `*mail*' buffer.  Each
header field starts with a field name at the beginning of a line, terminated by
a colon.  Upper and lower case are equivalent in field names (and in mailing
addresses also).  After the colon and optional whitespace comes the contents of
the field.

`To'
          This field contains the mailing addresses to which the message is
          addressed.

`Subject'
          The contents of the `Subject' field should be a piece of text that
          says what the message is about.  The reason `Subject' fields are
          useful is that most mail-reading programs can provide a summary of
          messages, listing the subject of each message but not its text.

`CC'
          This field contains additional mailing addresses to send the message
          to, but whose readers should not regard the message as addressed to
          them.

`BCC'
          This field contains additional mailing addresses to send the message
          to, which should not appear in the header of the message actually
          sent. Copies sent this way are called blind carbon copies.

          To send a blind carbon copy of every outgoing message to yourself,
          set the variable mail-self-blind to t.

`FCC'
          This field contains the name of one file (in system mail file format)
          to which a copy of the message should be appended when the message is
          sent.  Do not output directly into an Rmail file with FCC; instead,
          output to an inbox file and ``get new mail'' from that inbox file
          into the Rmail file.  See Rmail Inbox.

`From'
          Use the `From' field to say who you are, when the account you are
          using to send the mail is not your own.  The contents of the `From'
          field should be a valid mailing address, since replies will normally
          go there.

`Reply-to'
          Use this field to direct replies to a different address.  Most
          mail-reading programs (including Rmail) automatically send replies to
          the `Reply-to' address in preference to the `From' address. By adding
          a `Reply-to' field to your header, you can work around any problems
          your `From' address may cause for replies.

          If you want to put the same `Reply-to' address into every outgoing
          message, set the variable mail-default-reply-to to that address (as a
          string).

`In-reply-to'
          This field contains a piece of text describing a message you are
          replying to.  Some mail systems can use this information to correlate
          related pieces of mail.  Normally this field is filled in by Rmail
          when you are replying to a message in Rmail, and you never need to
          think about it (see Rmail).

The `To', `CC', `BCC' and `FCC' fields can appear any number of times, to
specify many places to send the message.

The `To', `CC', and `BCC' fields can have continuation lines.  All the lines
starting with whitespace, following the line on which the field starts, are
considered part of the field.  For example,

To: [e-mail], [e-mail],
  [e-mail]3281

 If the variable mail-archive-file-name is non-nil, it should be a string
naming a file; every time you start to edit a message to send, the message
starts out with an `FCC' field specifying that file.  Unless you remove the
`FCC' field before sending, the message will be written into that file when it
is sent.


ΓòÉΓòÉΓòÉ 29.3. Mail Aliases ΓòÉΓòÉΓòÉ

 You can define mail aliases in a file named `~/.mailrc'. These are short
mnemonic names stand for mail addresses or groups of mail addresses.  Like many
other mail programs, Emacs expands aliases when they occur in the `To', `CC',
and `BCC' fields.

 To define an alias in `~/.mailrc', write a line in the following format:

alias shortaddress fulladdress

For instance, if you send want to use maingnu as a short form of the address
[e-mail], put in the line:

alias maingnu [e-mail]

The file `~/.mailrc' is used primarily by other mail-reading programs; it can
contain various other commands.  Emacs ignores everything in it except for
alias definitions.

 Another way to define a mail alias, within Emacs alone, is with the
define-mail-alias command.  It prompts for the alias and then the full address.
You can use it to define aliases in your `.emacs' file, like this:

(define-mail-alias "maingnu" "[e-mail]")

 define-mail-alias records aliases by adding them to a variable named
mail-aliases.  If your are comfortable with manipulating Lisp lists, you can
set mail-aliases directly.  The initial value of mail-aliases is t, which means
that Emacs should read `.mailrc' to get the proper value.

 Normally, Emacs expands aliases when you send the message.  If you like, you
can have mail aliases expand as abbrevs, as soon as you type them in.  To
enable this feature, execute the following:

(add-hook 'mail-setup-hook 'mail-abbrevs-setup)

This can go in your `.emacs' file.  See Hooks.

 Note that abbrevs expand only if you insert a word-separator character
afterward.  However, any mail aliases that you didn't expand in the mail buffer
are expanded subsequently when you send the message. See Abbrevs.


ΓòÉΓòÉΓòÉ 29.4. Mail Mode ΓòÉΓòÉΓòÉ

 The major mode used in the `*mail*' buffer is Mail mode, which is much like
Text mode except that various special commands are provided on the C-c prefix.
These commands all have to do specifically with editing or sending the message.

C-c C-s
          Send the message, and leave the `*mail*' buffer selected (mail-send).

C-c C-c
          Send the message, and select some other buffer (mail-send-and-exit).

C-c C-f C-t
          Move to the `To' header field, creating one if there is none
          (mail-to).

C-c C-f C-s
          Move to the `Subject' header field, creating one if there is none
          (mail-subject).

C-c C-f C-c
          Move to the `CC' header field, creating one if there is none
          (mail-cc).

C-c C-w
          Insert the file `~/.signature' at the end of the message text
          (mail-signature).

C-c C-y
          Yank the selected message from Rmail (mail-yank-original). This
          command does nothing unless your command to start sending a message
          was issued with Rmail.

C-c C-q
          Fill all paragraphs of yanked old messages, each individually
          (mail-fill-yanked-message).

 There are two ways to send the message.  C-c C-s (mail-send) sends the message
and marks the `*mail*' buffer unmodified, but leaves that buffer selected so
that you can modify the message (perhaps with new recipients) and send it
again.  C-c C-c (mail-send-and-exit) sends and then deletes the window or
switches to another buffer.  It puts the `*mail*' buffer at the lowest priority
for reselection by default, since you are finished with using it.  This is the
usual way to send the message.

 Mail mode provides some other special commands that are useful for editing the
headers and text of the message before you send it.  There are three commands
defined to move point to particular header fields, all based on the prefix C-c
C-f (`C-f' is for ``field'').  They are C-c C-f C-t (mail-to) to move to the
`To' field, C-c C-f C-s (mail-subject) for the `Subject' field, and C-c C-f C-c
(mail-cc) for the `CC' field.  These fields have special motion commands
because they are the most common fields for the user to want to edit.

 C-c C-w (mail-signature) adds a standard piece text at the end of the message
to say more about who you are.  The text comes from the file `.signature' in
your home directory.

 To insert signatures automatically, set the variable mail-signature non-nil;
then starting a mail message automatically inserts the contents of your
`.signature' file.  If you want to omit your signature from a particular
message, delete it from the buffer before you send the message.

 When mail sending is invoked from the Rmail mail reader using an Rmail
command, C-c C-y can be used inside the `*mail*' buffer to insert the text of
the message you are replying to.  Normally it indents each line of that message
four spaces and eliminates most header fields.  A numeric argument specifies
the number of spaces to indent.  An argument of just C-u says not to indent at
all and not to eliminate anything. C-c C-y always uses the current message from
the `RMAIL' buffer, so you can insert several old messages by selecting one in
`RMAIL', switching to `*mail*' and yanking it, then switching back to `RMAIL'
to select another.

 You can specify the text for C-c C-y to insert at the beginning of each line:
set mail-yank-prefix to the desired string.  (A value of nil means to use
indentation; this is the default.) However, C-u C-c C-y never adds anything at
the beginning of the inserted lines, regardless of the value of
mail-yank-prefix.

 After using C-c C-y, you can use the command C-c C-q
(mail-fill-yanked-message) to fill the paragraphs of the yanked old message or
messages.  One use of C-c C-q fills all such paragraphs, each one individually.

 Mail mode defines the character `%' as part of a word; this is helpful for
using the word commands to edit mail addresses.

 Turning on Mail mode (which C-x m does automatically) runs the normal hooks
text-mode-hook and mail-mode-hook. Initializing a new outgoing message runs the
normal hook mail-setup-hook; if you want to add special fields to your mail
header or make other changes to the appearance of the mail buffer, use that
hook.  See Hooks.

 The main difference between these hooks is just when they are invoked.
Whenever you type M-x mail, mail-mode-hook runs as soon as the `*mail*' buffer
is created.  Then the mail-setup function puts in the default contents of the
buffer. After these default contents are inserted, mail-setup-hook runs.


ΓòÉΓòÉΓòÉ 29.5. Distracting the NSA ΓòÉΓòÉΓòÉ

 M-x spook adds a line of randomly chosen keywords to an outgoing mail message.
The keywords are chosen from a list of words that suggest you are discussing
something subversive.

 The idea behind this feature is that the suspicion that the NSA snoops on all
electronic mail messages that contain keywords suggesting they might be
interested.  (The NSA says they don't, but there is no way to be certain.)  The
idea is that if lots of people add suspicious words to their messages, the NSA
will get so busy with spurious input that they will have to give up reading it
all.

 Whether or not this confuses the NSA, it at least amuses people.


ΓòÉΓòÉΓòÉ 30. Reading Mail with Rmail ΓòÉΓòÉΓòÉ

 Rmail is an Emacs subsystem for reading and disposing of mail that you
receive.  Rmail stores mail messages in files called Rmail files. Reading the
message in an Rmail file is done in a special major mode, Rmail mode, which
redefines most letters to run commands for managing mail.  To enter Rmail, type
M-x rmail.  This reads your primary mail file, merges new mail in from your
inboxes, displays the first message you haven't read yet, and lets you begin
reading.

 Using Rmail in the simplest fashion, you have one Rmail file `~/RMAIL' in
which all of your mail is saved.  It is called your primary mail file.  In more
sophisticated usage, you can copy messages into other Rmail files and then edit
those files with Rmail.

 Rmail uses narrowing to hide all but one message in the Rmail file. The
message that is shown is called the current message.  Rmail mode's special
commands can do such things as delete the current message, copy into another
file, send a reply, or move to another message.

 Within the Rmail file, messages are arranged sequentially in order of receipt.
They are also assigned consecutive integers as their message numbers.  The
number of the current message is displayed in Rmail's mode line, followed by
the total number of messages in the file.  You can move to a message by
specifying its message number using the j key (see Rmail Motion).

 Following the usual conventions of Emacs, changes in an Rmail file become
permanent only when the file is saved.  You can do this with s (rmail-save),
which also expunges deleted messages from the file first (see Rmail Deletion).
To save the file without expunging, use C-x C-s.  Rmail saves the Rmail file
spontaneously when moving new mail from an inbox file (see Rmail Inbox).

 You can exit Rmail with q (rmail-quit); this expunges and saves the Rmail file
and then switches to another buffer.  But there is no need to `exit' formally.
If you switch from Rmail to editing in other buffers, and never happen to
switch back, you have exited.  (The Rmail command b, rmail-bury, does this for
you.)  Just make sure to save the Rmail file eventually (like any other file
you have changed).  C-x s is a good enough way to do this (see Saving).


ΓòÉΓòÉΓòÉ 30.1. Scrolling Within a Message ΓòÉΓòÉΓòÉ

 When Rmail displays a message that does not fit on the screen, it is necessary
to scroll through it.  This could be done with C-v, M-v and M-<, but in Rmail
scrolling is so frequent that it deserves to be easier to type.

SPC
          Scroll forward (scroll-up).

DEL
          Scroll backward (scroll-down).

.
          Scroll to start of message (rmail-beginning-of-message).

 Since the most common thing to do while reading a message is to scroll through
it by screenfuls, Rmail makes SPC and DEL synonyms of C-v (scroll-up) and M-v
(scroll-down)

 The command . (rmail-beginning-of-message) scrolls back to the beginning of
the selected message.  This is not quite the same as M-<: for one thing, it
does not set the mark; for another, it resets the buffer boundaries to the
current message if you have changed them.


ΓòÉΓòÉΓòÉ 30.2. Moving Among Messages ΓòÉΓòÉΓòÉ

 The most basic thing to do with a message is to read it.  The way to do this
in Rmail is to make the message current.  The usual practice is to move
sequentially through the file, since this is the order of receipt of messages.
When you enter Rmail, you are positioned at the first message that you have not
yet made current (that is, the first one that has the `unseen' attribute; see
Rmail Labels).  Move forward to see the other new messages; move backward to
reexamine old messages.

n
          Move to the next nondeleted message, skipping any intervening deleted
          messages (rmail-next-undeleted-message).

p
          Move to the previous nondeleted message
          (rmail-previous-undeleted-message).

M-n
          Move to the next message, including deleted messages
          (rmail-next-message).

M-p
          Move to the previous message, including deleted messages
          (rmail-previous-message).

j
          Move to the first message.  With argument n, move to message number n
          (rmail-show-message).

>
          Move to the last message (rmail-last-message).

<
          Move to the first message (rmail-first-message).

M-s regexp RET
          Move to the next message containing a match for regexp
          (rmail-search).

- M-s regexp RET
          Move to the previous message containing a match for regexp.

 n and p are the usual way of moving among messages in Rmail.  They move
through the messages sequentially, but skip over deleted messages, which is
usually what you want to do.  Their command definitions are named
rmail-next-undeleted-message and rmail-previous-undeleted-message.  If you do
not want to skip deleted messages---for example, if you want to move to a
message to undelete it---use the variants M-n and M-p (rmail-next-message and
rmail-previous-message).  A numeric argument to any of these commands serves as
a repeat count.

 In Rmail, you can specify a numeric argument by typing just the digits.  You
don't need to type C-u first.

 The M-s (rmail-search) command is Rmail's version of search.  The usual
incremental search command C-s works in Rmail, but it searches only within the
current message.  The purpose of M-s is to search for another message.  It
reads a regular expression (see Regexps) nonincrementally, then searches
starting at the beginning of the following message for a match.  The message
containing the match is selected.

 If regexp is empty, M-s reuses the regexp used the previous time.

 To search backward in the file for another message, give M-s a negative
argument.  In Rmail you can do this with - M-s.

 It is also possible to search for a message based on labels. See Rmail Labels.

 To move to a message specified by absolute message number, use j
(rmail-show-message) with the message number as argument.  With no argument, j
selects the first message.  > (rmail-last-message) selects the last message.  <
(rmail-first-message) selects the first message.


ΓòÉΓòÉΓòÉ 30.3. Deleting Messages ΓòÉΓòÉΓòÉ

 When you no longer need to keep a message, you can delete it.  This flags it
as ignorable, and some Rmail commands pretend it is no longer present; but it
still has its place in the Rmail file, and still has its message number.

 Expunging the Rmail file actually removes the deleted messages. The remaining
messages are renumbered consecutively.  Expunging is the only action that
changes the message number of any message, except for undigestifying (see Rmail
Digest).

d
          Delete the current message, and move to the next nondeleted message
          (rmail-delete-forward).

C-d
          Delete the current message, and move to the previous nondeleted
          message (rmail-delete-backward).

u
          Undelete the current message, or move back to a deleted message and
          undelete it (rmail-undelete-previous-message).

x
          Expunge the Rmail file (rmail-expunge).

 There are two Rmail commands for deleting messages.  Both delete the current
message and select another message.  d (rmail-delete-forward) moves to the
following message, skipping messages already deleted, while C-d
(rmail-delete-backward) moves to the previous nondeleted message. If there is
no nondeleted message to move to in the specified direction, the message that
was just deleted remains current.

 To make all the deleted messages finally vanish from the Rmail file, type x
(rmail-expunge).  Until you do this, you can still undelete the deleted
messages.

 To undelete, type u (rmail-undelete-previous-message), which is designed to
cancel the effect of a d command (usually).  It undeletes the current message
if the current message is deleted.  Otherwise it moves backward to previous
messages until a deleted message is found, and undeletes that message.

 You can usually undo a d with a u because the u moves back to and undeletes
the message that the d deleted.  But this does not work when the d skips a few
already-deleted messages that follow the message being deleted; then the u
command undeletes the last of the messages that were skipped.  There is no
clean way to avoid this problem.  However, by repeating the u command, you can
eventually get back to the message that you intend to undelete.  You can also
select a particular deleted message with M-p command, then type u to undelete
it.

 A deleted message has the `deleted' attribute, and as a result `deleted'
appears in the mode line when the current message is deleted.  In fact,
deleting or undeleting a message is nothing more than adding or removing this
attribute.  See Rmail Labels.


ΓòÉΓòÉΓòÉ 30.4. Rmail Files and Inboxes ΓòÉΓòÉΓòÉ

 Unix places incoming mail for you in a file that we call your inbox.  When you
start up Rmail, it copies the new messages from your inbox into your primary
mail file, an Rmail file, which also contains other messages saved from
previous Rmail sessions.  It is in this file that you actually read the mail
with Rmail.  This operation is called getting new mail.  It can be repeated at
any time using the g key in Rmail.  The inbox file name is
`/usr/spool/mail/username' on some systems (typically Berkeley-derived ones)
and `/usr/mail/username' on other systems.

 There are three reason for having separate Rmail files and inboxes.

 1. The inbox file format varies between operating systems and according to the
    other mail software in use.  Only one part of Rmail needs to know about the
    alternatives, and it need only understand how to convert all of them to
    Rmail's own format.

 2. The inbox file format usually doesn't provide a place for all the
    information that Rmail records.

 3. It is very cumbersome to access an inbox file without danger of losing
    mail, because it is necessary to interlock with mail delivery. Moreover,
    different operating systems use different interlocking techniques.  The
    strategy of moving mail out of the inbox once and for all into a separate
    Rmail file avoids the need for interlocking in all the rest of Rmail, since
    only Rmail operates on the Rmail file.

 When getting new mail, Rmail first copies the new mail from the inbox file to
the Rmail file; then it saves the Rmail file; then it truncates the inbox file.
This way, a system crash may cause duplication of mail between the inbox and
the Rmail file, but cannot lose mail.

 Copying mail from an inbox in the system's mailer directory actually puts it
in an intermediate file `~/.newmail'.  This is because the interlocking is done
by a C program that copies to another file. `~/.newmail' is deleted after mail
merging is successful.  If there is a crash at the wrong time, this file
continues to exist and will be used as an inbox the next time you get new mail.


ΓòÉΓòÉΓòÉ 30.5. Multiple Mail Files ΓòÉΓòÉΓòÉ

 Rmail operates by default on your primary mail file, which is named `~/RMAIL'
and receives your incoming mail from your system inbox file. But you can also
have other mail files and edit them with Rmail.  These files can receive mail
through their own inboxes, or you can move messages into them with explicit
Rmail commands (see Rmail Output).

i file RET
          Read file into Emacs and run Rmail on it (rmail-input).

M-x set-rmail-inbox-list RET files RET
          Specify inbox file names for current Rmail file to get mail from.

g
          Merge new mail from current Rmail file's inboxes
          (rmail-get-new-mail).

C-u g file RET
          Merge new mail from inbox file file.

 To run Rmail on a file other than your primary mail file, you may use the i
(rmail-input) command in Rmail.  This visits the file, puts it in Rmail mode,
and then gets new mail from the file's inboxes if any.  The file should be in
Rmail format.  You can use M-x rmail-input even when not in Rmail.

 The file you read with i should usually be a valid Rmail file. If it is not,
then Rmail tries to decompose it into a stream of messages in various known
formats.  If it succeeds, it converts the whole file to an Rmail file.

 Each Rmail file can contain a list of inbox file names; you can specify this
list with M-x set-rmail-inbox-list RET files RET.  The argument can contain any
number of file names, separated by commas.  It can also be empty, which
specifies that this file should have no inboxes.  Once a list of inboxes is
specified, the Rmail file remembers it permanently until it is explicitly
changed.

 If an Rmail file has inboxes, new mail is merged in from the inboxes when the
Rmail file is brought into Rmail, and when you use the g (rmail-get-new-mail)
command.  If the Rmail file specifies no inboxes, then no new mail is merged in
at these times.  As a special exception, if your primary mail file does not
specify any inbox files, it uses the standard system inbox.

 To merge mail from a file that is not the usual inbox, give the g key a
numeric argument, as in C-u g.  Then it reads a file name and merges mail from
that file.  The inbox file is not deleted or changed in any way when g with an
argument is used.  This is, therefore, a general way of merging one file of
messages into another.


ΓòÉΓòÉΓòÉ 30.6. Copying Messages Out to Files ΓòÉΓòÉΓòÉ

o file RET
          Append a copy of the current message to the file file, writing it in
          Rmail file format (rmail-output-to-rmail-file).

C-o file RET
          Append a copy of the current message to the file file, writing it in
          Unix mail file format (rmail-output).

 If an Rmail file has no inboxes, the only way messages get into it is by means
of explicit o commands.

 o (rmail-output-to-rmail-file) appends the current message in Rmail format to
the end of the specified file.  This is the best command to use to move
messages between Rmail files.  If the other Rmail file is currently visited,
the copying is done into the other file's Emacs buffer instead.  You should
eventually save it on disk.

 The C-o (rmail-output) command in Rmail appends a copy of the current message
to a specified file, in inbox file format.  This is useful for moving messages
into files to be read by other mail processors that do not understand Rmail
format.

 The o and C-o commands are actually equivalent when you specify an existing
file; both commands check the file's contents to determine which format to use
(Rmail or inbox).  Which command you use makes a difference when you specify a
nonexistent file.

 Copying a message with o or C-o gives the original copy of the message the
`filed' attribute, so that `filed' appears in the mode line when such a message
is current.  If you like to keep just a single copy of every mail message, set
the variable rmail-delete-after-output to t; then the o and C-o commands delete
the original message after copying it. (You can undelete the original
afterward.)

 The variable rmail-output-file-alist lets you specify intelligent defaults for
the output file, based on the contents of the current message.  The value
should be a list whose elements have this form:

(regexp . filename)

If there's a match for regexp in the current message, then the default file
name for output is filename.  If multiple elements match the message, the first
matching element decides the default file name.


ΓòÉΓòÉΓòÉ 30.7. Labels ΓòÉΓòÉΓòÉ

 Each message can have various labels assigned to it as a means of
classification.  A label has a name; different names mean different labels. Any
given label is either present or absent on a particular message.  A few label
names have standard meanings and are given to messages automatically by Rmail
when appropriate; these special labels are called attributes. All other labels
are assigned only by users.

a label RET
          Assign the label label to the current message (rmail-add-label).

k label RET
          Remove the label label from the current message (rmail-kill-label).

C-M-n labels RET
          Move to the next message that has one of the labels labels
          (rmail-next-labeled-message).

C-M-p labels RET
          Move to the previous message that has one of the labels labels
          (rmail-previous-labeled-message).

C-M-l labels RET
          Make a summary of all messages containing any of the labels labels
          (rmail-summary-by-labels).

Specifying an empty string for one these commands means to use the last label
specified for any of these commands.

 The a (rmail-add-label) and k (rmail-kill-label) commands allow you to assign
or remove any label on the current message.  If the label argument is empty, it
means to assign or remove the same label most recently assigned or removed.

 Once you have given messages labels to classify them as you wish, there are
two ways to use the labels: in moving and in summaries.

 The command C-M-n labels RET (rmail-next-labeled-message) moves to the next
message that has one of the labels labels.  The argument labels specifies one
or more label names, separated by commas.  C-M-p
(rmail-previous-labeled-message) is similar, but moves backwards to previous
messages.  A preceding numeric argument to either one serves as a repeat count.

 The command C-M-l labels RET (rmail-summary-by-labels) displays a summary
containing only the messages that have at least one of a specified set of
messages.  The argument labels is one or more label names, separated by commas.
See Rmail Summary, for information on summaries.

 If the labels argument to C-M-n, C-M-p or C-M-l is empty, it means to use the
last set of labels specified for any of these commands.

 Some labels such as `deleted' and `filed' have built-in meanings and are
assigned to or removed from messages automatically at appropriate times; these
labels are called attributes.  Here is a list of Rmail attributes:

`unseen'
          Means the message has never been current.  Assigned to messages when
          they come from an inbox file, and removed when a message is made
          current.  When you start Rmail, it initially shows the first message
          that has this attribute.

`deleted'
          Means the message is deleted.  Assigned by deletion commands and
          removed by undeletion commands (see Rmail Deletion).

`filed'
          Means the message has been copied to some other file.  Assigned by
          the file output commands (see Rmail Files).

`answered'
          Means you have mailed an answer to the message.  Assigned by the r
          command (rmail-reply).  See Rmail Reply.

`forwarded'
          Means you have forwarded the message to other users.  Assigned by the
          f command (rmail-forward).  See Rmail Reply.

`edited'
          Means you have edited the text of the message within Rmail. See Rmail
          Editing.

`resent'
          Means you have resent the message to other users.  Assigned by the
          command M-x rmail-resend.  See Rmail Reply.

 All other labels are assigned or removed only by the user, and have no
standard meaning.


ΓòÉΓòÉΓòÉ 30.8. Sending Replies ΓòÉΓòÉΓòÉ

 Rmail has several commands that use Mail mode to send outgoing mail. See
Sending Mail, for information on using Mail mode.  What are documented here are
the special commands of Rmail for entering Mail mode. Note that the usual keys
for sending mail, C-x m and C-x 4 m, are available in Rmail mode and work just
as they usually do.

m
          Send a message (rmail-mail).

c
          Continue editing already started outgoing message
          (rmail-continue).

r
          Send a reply to the current Rmail message (rmail-reply).

f
          Forward current message to other users (rmail-forward).

C-u f
          Resend the current message to other users (rmail-resend).

M-m
          Try sending a bounced message a second time (rmail-retry-failure).

 The most common reason to send a message while in Rmail is to reply to the
message you are reading.  To do this, type r (rmail-reply).  This displays the
`*mail*' buffer in another window, much like C-x 4 m, but preinitializes the
`Subject', `To', `CC' and `In-reply-to' header fields based on the message you
are replying to.  The `To' field is starts out as the address of the person who
sent the message you received, and the `CC' field starts out with all the other
recipients of that message.

 You can exclude certain recipients from being placed automatically in the
`CC', using the variable rmail-dont-reply-to-names.  Its value should be a
regular expression (as a string); any recipient that the regular expression
matches, is excluded from the `CC' field. The default value matches your own
name, and any name starting with `info-'.  (Those names are excluded because
there is a convention of using them for large mailing lists to broadcast
announcements.)

 To omit the `CC' field completely for a particular reply, enter the reply
command with a prefix argument: C-u r.

 Once the `*mail*' buffer has been initialized, editing and sending the mail
goes as usual (see Sending Mail).  You can edit the presupplied header fields
if they are not right for you.  You can also use the commands of Mail mode,
including C-c C-y to yank in the message that you are replying to, and C-c C-q
to fill what was thus yanked.  You can also switch to the Rmail buffer, select
a different message, switch back, and yank the new current message.

 Sometimes a message does not reach its destination.  Mailers usually send the
failed message back to you, enclosed in a failure message.  The Rmail command
M-m (rmail-retry-failure) prepares to send the same message a second time: it
sets up a `*mail*' buffer with the same text and header fields as before.  If
you type C-c C-c right away, you send the message again exactly the same as the
first time.  Alternatively, you can edit the text or headers and then send it.

 Another frequent reason to send mail in Rmail is to forward the current
message to other users.  f (rmail-forward) makes this easy by preinitializing
the `*mail*' buffer with the current message as the text, and a subject
designating a forwarded message.  All you have to do is fill in the recipients
and send.  When you forward a message, recipients get a message which is
``from'' you, and which has the original message in its contents.

 Resending is an alternative similar to forwarding; the difference is that
resending sends a message that is ``from'' the original sender, just as it
reached you---with a few added header fields `Resent-from' and `Resent-to' to
indicate that it came via you.  To resend a message in Rmail, use C-u f.  (f
runs rmail-forward, which is programmed to invoke rmail-resend if you provide a
numeric argument.)

 The m (rmail-mail) command is used to start editing an outgoing message that
is not a reply.  It leaves the header fields empty. Its only difference from
C-x 4 m is that it makes the Rmail buffer accessible for C-c C-y, just as r
does.  Thus, m can be used to reply to or forward a message; it can do anything
r or f can do.

 The c (rmail-continue) command resumes editing the `*mail*' buffer, to finish
editing an outgoing message you were already composing, or to alter a message
you have sent.

 If you set the variable rmail-mail-new-frame to a non-nil value, then all the
Rmail commands to start sending a message create a new frame to edit it in.
This frame is deleted when you send the message, or when you use the `Don't
Send' item in the `Mail' menu.


ΓòÉΓòÉΓòÉ 30.9. Summaries ΓòÉΓòÉΓòÉ

 A summary is a buffer containing one line per message to give you an overview
of the mail in an Rmail file.  Each line shows the message number, the sender,
the labels, and the subject.  When the summary buffer is selected, you can use
almost all Rmail commands; these apply to the message described by the current
line of the summary.  Moving point in the summary buffer selects messages as
you move to their summary lines.

 A summary buffer applies to a single Rmail file only; if you are editing
multiple Rmail files, each one has its own summary buffer (if you have asked
for one).  The summary buffer name is made by appending `-summary' to the Rmail
buffer's name.  Normally only one summary buffer is displayed at a time.


ΓòÉΓòÉΓòÉ 30.9.1. Making Summaries ΓòÉΓòÉΓòÉ

 Here are the commands to create a summary for the current Rmail file. Once the
Rmail file has a summary buffer, changes in the Rmail file (such as deleting or
expunging messages, and getting new mail) automatically update the summary.

h
C-M-h
          Summarize all messages (rmail-summary).

l labels RET
C-M-l labels RET
          Summarize message that have one or more of the specified labels
          (rmail-summary-by-labels).

C-M-r rcpts RET
          Summarize messages that have one or more of the specified recipients
          (rmail-summary-by-recipients).

C-M-t topic RET
          Summarize messages that have a match for the specified regexp topic
          in their subjects (rmail-summary-by-topic).

 The h or C-M-h (rmail-summary) command fills the summary buffer for the
current Rmail file with a summary of all the messages in the file. It then
displays and selects the summary buffer in another window.

 C-M-l labels RET (rmail-summary-by-labels) makes a partial summary mentioning
only the messages that have one or more of the labels labels.  labels should
contain label names separated by commas.

 C-M-r rcpts RET (rmail-summary-by-recipients) makes a partial summary
mentioning only the messages that have one or more of the recipients rcpts.
rcpts should contain mailing addresses separated by commas.

 C-M-t topic RET (rmail-summary-by-topic) makes a partial summary mentioning
only the messages whose subjects have a match for the regular expression topic.

 Note that there is only one summary buffer for any Rmail file; making one kind
of summary discards any previously made summary.


ΓòÉΓòÉΓòÉ 30.9.2. Editing in Summaries ΓòÉΓòÉΓòÉ

 You can use the Rmail summary buffer to do almost anything you can do in the
Rmail buffer itself.  In fact, once you have a summary buffer, there's no need
to switch back to the Rmail buffer.

 You can select and display various messages in the Rmail buffer, from the
summary buffer, just by moving point in the summary buffer to different lines.
It doesn't matter what Emacs command you use to move point; whichever line
point is on at the end of the command, that message is selected in the Rmail
buffer.

 Almost all Rmail commands work in the summary buffer as well as in the Rmail
buffer.  Thus, d in the summary buffer deletes the current message, u
undeletes, and x expunges.  o and C-o output the current message to a file; r
starts a reply to it.  You can scroll the current message while remaining in
the summary buffer using SPC and DEL.

 The Rmail commands to move between messages also work in the summary buffer,
but with a twist: they move through the set of messages included in the
summary.  They also redisplay the Rmail buffer on the screen (unlike cursor
motion commands, which update the contents of the Rmail buffer but don't
display it in a window unless it already appears). Here is a list of these
commands:

n
          Move to next line, skipping lines saying `deleted', and select its
          message.

p
          Move to previous line, skipping lines saying `deleted', and select
          its message.

M-n
          Move to next line and select its message.

M-p
          Move to previous line and select its message.

>
          Move to the last line, and select its message.

<
          Move to the first line, and select its message.

M-s pattern RET
          Search through messages for pattern starting with the current
          message; select the message found, and move point in the summary
          buffer to that message's line.

 Deletion, undeletion, and getting new mail, and even selection of a different
message all update the summary buffer when you do them in the Rmail buffer.  If
the variable rmail-redisplay-summary is non-nil, these actions also bring the
summary buffer back onto the screen.

 When you are finished using the summary, type w (rmail-summary-wipe) to kill
the summary buffer's window.  You can also exit Rmail while in the summary.  q
(rmail-summary-quit) kills the summary window, then saves the Rmail file and
switches to another buffer.


ΓòÉΓòÉΓòÉ 30.10. Editing Within a Message ΓòÉΓòÉΓòÉ

 Rmail mode provides a few special commands for moving within and editing the
current message.  In addition, the usual Emacs commands are available (except
for a few, such as C-M-n and C-M-h, that are redefined by Rmail for other
purposes).  However, the Rmail buffer is normally read-only, and to alter it
you must use the Rmail command e described below.

t
          Toggle display of original headers (rmail-toggle-headers).

e
          Edit current message (rmail-edit-current-message).

 Rmail reformats the header of each message before displaying it. Normally this
involves deleting most header fields, on the grounds that they are not
interesting.  The variable rmail-ignored-headers specifies a regexp that
matches the header fields to discard in this way.  The original headers are
saved permanently, and to see what they look like, use the t command
(rmail-toggle-headers).  This discards the reformatted headers of the current
message and displays it with the original headers.  Repeating t reformats the
message again.  Selecting the message again also reformats.

 The Rmail buffer is normally read only, and most of the characters you would
type to modify it (including most letters) are redefined as Rmail commands.
This is usually not a problem since it is rare to want to change the text of a
message.  When you do want to do this, the way is to type e
(rmail-edit-current-message), which changes from Rmail mode into Rmail Edit
mode, another major mode which is nearly the same as Text mode. The mode line
indicates this change.

 In Rmail Edit mode, letters insert themselves as usual and the Rmail commands
are not available.  When you are finished editing the message and are ready to
go back to Rmail, type C-c C-c, which switches back to Rmail mode.
Alternatively, you can return to Rmail mode but cancel all the editing that you
have done by typing C-c C-].

 Entering Rmail Edit mode runs the hook text-mode-hook; then it runs the hook
rmail-edit-mode-hook (see Hooks).  It adds the attribute `edited' to the
message.


ΓòÉΓòÉΓòÉ 30.11. Digest Messages ΓòÉΓòÉΓòÉ

 A digest message is a message which exists to contain and carry several other
messages.  Digests are used on some moderated mailing lists; all the messages
that arrive for the list during a period of time such as one day are put inside
a single digest which is then sent to the subscribers.  Transmitting the single
digest uses much less computer time than transmitting the individual messages
even though the total size is the same, because the per-message overhead in
network mail transmission is considerable.

 When you receive a digest message, the most convenient way to read it is to
undigestify it: to turn it back into many individual messages. Then you can
read and delete the individual messages as it suits you.

 To do this, type M-x undigestify-rmail-message after selecting the digest
message.  This extracts the submessages as separate Rmail messages, and inserts
them following the digest.  The digest message itself is flagged as deleted.


ΓòÉΓòÉΓòÉ 30.12. Converting an Rmail File to Mailbox Format ΓòÉΓòÉΓòÉ

 The command M-x unrmail converts a file in Rmail format to ordinary system
mailbox format, so that you can use it with other mail-editing tools.  You must
specify two arguments, the name of the Rmail file and the name to use for the
converted file. M-x unrmail does not alter the Rmail file itself.


ΓòÉΓòÉΓòÉ 30.13. Reading Rot13 Messages ΓòÉΓòÉΓòÉ

 Mailing list messages that might offend some readers are sometimes encoded in
a simple code called rot13---so named because it rotates the alphabet by 13
letters.  This code is not for secrecy, as it provides none; rather, it enables
those who might be offended to avoid ever seeing the real text of the message.

 To view a buffer using the rot13 code, use the command M-x rot13-other-window.
This displays the current buffer in another window which applies the code when
displaying the text.


ΓòÉΓòÉΓòÉ 31. Dired, the Directory Editor ΓòÉΓòÉΓòÉ

 Dired makes an Emacs buffer containing a listing of a directory, and
optionally some of its subdirectories as well.  You can use the normal Emacs
commands to move around in this buffer, and special Dired commands to operate
on the files listed.


ΓòÉΓòÉΓòÉ 31.1. Entering Dired ΓòÉΓòÉΓòÉ

 To invoke Dired, do C-x d or M-x dired.  The command reads a directory name or
wildcard file name pattern as a minibuffer argument to specify which files to
list.  Where dired differs from list-directory is in putting the buffer into
Dired mode so that the special commands of Dired are available.

 The variable dired-listing-switches specifies the options to give to ls for
listing directory; this string must contain `-l'.  If you use a numeric prefix
argument with the dired command, you can specify the ls switches with the
minibuffer after you finish entering the directory specification.

 To display the Dired buffer in another window rather than in the selected
window, use C-x 4 d (dired-other-window) instead of C-x d.


ΓòÉΓòÉΓòÉ 31.2. Commands in the Dired Buffer ΓòÉΓòÉΓòÉ

  The Dired buffer is ``read-only'', and inserting text in it is not useful, so
ordinary printing characters such as d and x are used for special Dired
commands.  Some Dired commands mark or flag the current file (that is, the file
on the current line); other commands operate on the marked files or on the
flagged files.

 All the usual Emacs cursor motion commands are available in Dired buffers.
Some special purpose cursor motion commands are also provided.  The keys C-n
and C-p are redefined to put the cursor at the beginning of the file name on
the line, rather than at the beginning of the line.

 For extra convenience, SPC and n in Dired are equivalent to C-n.  p is
equivalent to C-p.  (Moving by lines is so common in Dired that it deserves to
be easy to type.)  DEL (move up and unflag) is often useful simply for moving
up.


ΓòÉΓòÉΓòÉ 31.3. Deleting Files with Dired ΓòÉΓòÉΓòÉ

 The primary use of Dired is to flag files for deletion and then delete the
files previously flagged.

d
          Flag this file for deletion.

u
          Remove deletion flag on this line.

DEL
          Move point to previous line and remove the deletion flag on that
          line.

x
          Delete the files that are flagged for deletion.

#
          Flag all auto-save files (files whose names start and end with `#')
          for deletion (see Auto Save).

~
          Flag all backup files (files whose names end with `~') for deletion
          (see Backup).

. (Period)
          Flag excess numeric backup files for deletion.  The oldest and newest
          few backup files of any one file are exempt; the middle ones are
          flagged.

% d regexp RET
          Flag for deletion all files whose names match the regular expression
          regexp (dired-flag-files-regexp).  This is just like % m except that
          it uses `D' instead of `*' to mark the files.

          Only the non-directory part of the file name is used in matching.
          Use `^' and `$' to anchor matches.  Exclude subdirectories by hiding
          them (see Hiding Subdirectories).

 You can flag a file for deletion by moving to the line describing the file and
typing d.  The deletion flag is visible as a `D' at the beginning of the line.
This command moves point to the beginning of the next line, so that repeated d
commands flag successive files.

 The files are flagged for deletion rather than deleted immediately to reduce
the danger of deleting a file accidentally.  Until you direct Dired to expunge
the flagged files, you can remove deletion flags using the commands u and DEL.
u works just like d, but removes flags rather than making flags.  DEL moves
upward, removing flags; it is like u with numeric argument automatically
negated.

 To delete the flagged files, type x (dired-expunge). This command first
displays a list of all the file names flagged for deletion, and requests
confirmation with yes.  Once you confirm, x deletes all the flagged files, then
deletes their lines from the text of the Dired buffer.  The shortened Dired
buffer remains selected.

 If you answer no or quit with C-g when asked to confirm, you return
immediately to Dired, with the deletion flags still present in the buffer, and
no files actually deleted.

 The #, ~ and . commands flag many files for deletion, based on their file
names.  These commands are useful precisely because they do not actually delete
any files; you can remove the deletion flags from any flagged files that you
really wish to keep.

 # flags for deletion all files whose names look like auto-save files (see Auto
Save)---that is, files whose names begin and end with `#'.  ~ flags for
deletion all files whose names say they are backup files (see Backup)---that
is, whose names end in `~'.

 . (Period) flags just some of the backup files for deletion: all but the
oldest few and newest few backups of any one file.  Normally
dired-kept-versions (*not* kept-new-versions; that applies only when saving)
specifies the number of newest versions of each file to keep, and
kept-old-versions specifies the number of oldest versions to keep.

 Period with a positive numeric argument, as in C-u 3 ., specifies the number
of newest versions to keep, overriding dired-kept-versions.  A negative numeric
argument overrides kept-old-versions, using minus the value of the argument to
specify the number of oldest versions of each file to keep.

 The % d command flags all files whose names match a specified regular
expression (dired-flag-files-regexp).  Only the non-directory part of the file
name is used in matching.  You can use `^' and `$' to anchor matches.  You can
exclude subdirectories by hiding them (see Hiding Subdirectories).


ΓòÉΓòÉΓòÉ 31.4. Visiting Files in Dired ΓòÉΓòÉΓòÉ

 There are several Dired commands for visiting or examining the files listed in
the Dired buffer.  All of them apply to the current line's file; if that file
is really a directory, these commands invoke Dired on that subdirectory (using
a separate Dired buffer).

f
          Visit the file described on the current line, like typing C-x C-f and
          supplying that file name (dired-find-file).  See Visiting.

o
          Like f, but uses another window to display the file's buffer
          (dired-find-file-other-window).  The Dired buffer remains visible in
          the first window.  This is like using C-x 4 C-f to visit the file.
          See Windows.

C-o
          Visit the file described on the current line, and display the buffer
          in another window, but do not select that window
          (dired-display-file).

v
          View the file described on the current line, using M-x view-file
          (dired-view-file).

          Viewing a file is like visiting it, but is slanted toward moving
          around in the file conveniently and does not allow changing the file.
          See Misc File Ops.


ΓòÉΓòÉΓòÉ 31.5. Dired Marks vs. Flags ΓòÉΓòÉΓòÉ

 Instead of flagging a file with `D', you can mark the file with some other
character (usually `*').  Most Dired commands other than ``expunge'' (x)
operate on files marked with `*'.

 Here are some commands for marking with `*' (and also for unmarking).  (See
Dired Deletion, for commands to flag and unflag files.)

m
          Mark the current file with `*' (dired-mark).  With a numeric argument
          n, mark the next n files starting with the current file.  (If n is
          negative, mark the previous -n files.)

*
          Mark all executable files with `*' (dired-mark-executables).  With a
          prefix argument, unmark all those files.

@
          Mark all symbolic links with `*' (dired-mark-symlinks). With a prefix
          argument, unmark all those files.

/
          Mark with `*' all files which are actually directories, except for
          `.' and `..' (dired-mark-directories).  With a prefix argument,
          unmark all those files.

M-DEL markchar
          Remove all marks that use the character markchar
          (dired-unmark-all-files).  If you specify RET as markchar, this
          command removes all marks, no matter what the marker character is.

          With a numeric argument, this command queries about each marked file,
          asking whether to remove its mark.  You can answer y meaning yes, n
          meaning no, ! to remove the marks from the remaining files without
          asking about them.

c old new
          Replace all marks that use the character old with marks that use the
          character new (dired-change-marks).  This command is the only way to
          create or use marks other than `*' or `D'. The arguments are single
          characters---do not use RET to terminate them.

          You can use almost any character as a mark character by means of this
          command, to distinguish various classes of files.  If old is a space
          (`'), then the command operates on all unmarked files; if new is a
          space, then the command unmarks the files it acts on.

          To illustrate the power of this command, here is how to put `*' marks
          on all the files that are unmarked, while unmarking all those that
          have `*' marks:

                    c * t  c SPC *  c t SPC

% m regexp RET
          Mark (with `*') all files whose names match the regular expression
          regexp (dired-mark-files-regexp).

          Only the non-directory part of the file name is used in matching.
          Use `^' and `$' to anchor matches.  Exclude subdirectories by hiding
          them (see Hiding Subdirectories).


ΓòÉΓòÉΓòÉ 31.6. Operating on Files ΓòÉΓòÉΓòÉ

 This section describes the basic Dired commands to operate on one file or
several files.  All of these commands are capital letters; all of them use the
minibuffer, either to read an argument or to ask for confirmation, before they
act.  All use the following convention to decide which files to manipulate:

o If you give the command a numeric prefix argument n, it operates on the next
  n files, starting with the current file.  (If n is negative, the command
  operates on the -n files preceding the current line.)

o Otherwise, if some files are marked with `*', the command operates on all
  those files.

o Otherwise, the command operates on the current file only.

Here are the commands that operate on files in this way:

C new RET
          Copy the specified files (dired-do-copy).  The argument new is the
          directory to copy into, or (if copying a single file) the new name.

          If dired-copy-preserve-time is non-nil, then copying with this
          command sets the modification time of the new file to be the same as
          that of the old file.

R new RET
          Rename the specified files (dired-do-rename).  The argument new is
          the directory to rename into, or (if renaming a single file) the new
          name.

          Dired automatically changes the visited file name of buffers
          associated with renamed files so that they refer to the new names.

H new RET
          Make hard links to the specified files (dired-do-hardlink).  The
          argument new is the directory to make the links in, or (if making
          just one link) the name to give the link.

S new RET
          Make symbolic links to the specified files (dired-do-symlink). The
          argument new is the directory to make the links in, or (if making
          just one link) the name to give the link.

M modespec RET
          Change the mode (also called ``permission bits'') of the specified
          files (dired-do-chmod).  This calls the chmod program, so modespec
          can be any argument that chmod can handle.

G newgroup RET
          Change the group of the specified files to newgroup (dired-do-chgrp).

O newowner RET
          Change the owner of the specified files to newowner (dired-do-chown).
          (On most systems, only the superuser can do this.)

          The variable dired-chown-program specifies the name of the program to
          use to do the work (different systems put chown in different places).

P command RET
          Print the specified files (dired-do-print).  You must specify the
          command to print them with, but the minibuffer starts out with a
          suitable guess made using the variables lpr-command and lpr-switches
          (the same variables that lpr-file uses; see Hardcopy).

Z
          Compress or uncompress the specified files (dired-do-compress). If
          the file appears to be a compressed file, it is uncompressed;
          otherwise, it is compressed.

L
          Load the specified Emacs Lisp files (dired-do-load). See Lisp
          Libraries.

B
          Byte compile the specified Emacs Lisp files (dired-do-byte-compile).
          See Byte Compilation.


ΓòÉΓòÉΓòÉ 31.7. Shell Commands in Dired ΓòÉΓòÉΓòÉ

The dired command ! (dired-do-shell-command) reads a shell command string in
the minibuffer and runs the shell command on all the specified files.  There
are two ways of applying a shell command to multiple files:

o If you use `*' in the shell command, then it runs just once, with the list of
  file names substituted for the `*'.  The order of file names is the order of
  appearance in the Dired buffer.

  Thus, ! tar cf foo.tar * RET runs tar on the entire list of file names,
  putting them into one tar file `foo.tar'.

o If the command string doesn't contain `*', then it runs once for each file,
  with the file name added at the end.

  For example, ! uudecode RET runs uudecode on each file.

What if you want to run the shell command once for each file but with the file
name inserted in the middle?  Or if you want to use the file names in a more
complicated fashion?  Use a shell loop.  For example, this shell command would
run uuencode on each of the specified files, writing the output into a
corresponding `.uu' file:

for file in *; uuencode $file $file >$file.uu; done

The working directory for the shell command is the top level directory of the
Dired buffer.

The ! command does not attempt to update the Dired buffer to show new or
modified files, because it doesn't really understand shell commands, and does
not know what files the shell command changed.  Use the g command to update the
Dired buffer ( see Dired Updating).


ΓòÉΓòÉΓòÉ 31.8. Transforming File Names in Dired ΓòÉΓòÉΓòÉ

 Here are commands that alter file names in a systematic way:

% u
          Rename each of the selected files to an upper case name
          (dired-upcase).  If the old file names are `Foo' and `bar', the new
          names are `FOO' and `BAR'.

% l
          Rename each of the selected files to a lower case name
          (dired-downcase).  If the old file names are `Foo' and `bar', the new
          names are `foo' and `bar'.

% R from RET to RET
% C from RET to RET
% H from RET to RET
% S from RET to RET
          These four commands rename, copy, make hard links and make soft
          links, in each case computing the new name by regular expression
          substitution from the name of the old file.

 The four regular expression substitution commands effectively perform
query-replace-regexp on the selected file names in the Dired buffer.  They read
two arguments: a regular expression from, and a substitution pattern to.

 The commands match each ``old'' file name against the regular expression from,
and then replace the matching part with to.  You can use `\&' and `\digit' in
to to refer to all or part of the old file name, as in query-replace (see Query
Replace).

 For example, % R ^.*$ RET x-\& RET renames each selected file by prepending
`x-' to its name.  The inverse of this, removing `x-' from the front of each
file name, is also possible: one method is % R ^x-.*$ RET \& RET; another is %
R ^x- RET RET.  (Use `^' and `$' to anchor matches that should span the whole
filename.)

 If the regular expression matches more than once in a file name, only the
first match is replaced.

 Normally, the replacement process does not consider the files' directory
names; it operates on the file name within the directory.  If you specify a
prefix argument of zero, then replacement affects the entire absolute file name
including directory name.

 Often you will want to apply the command to all files matching the same regexp
that you use in the command.  To do this, mark those files with % m regexp RET,
then use the same regular expression in the command to operate on the files.
To make this easier, the commands to operate use the last regular expression
specified in a % command as a default.


ΓòÉΓòÉΓòÉ 31.9. File Comparison with Dired ΓòÉΓòÉΓòÉ

 Here are two Dired commands that compare specified files using diff.

=
          Compare the current file (the file at point) with another file (the
          file at the mark) using the diff program (dired-diff).  The file at
          the mark is the first argument of diff, and the file at point is the
          second argument.

M-=
          Compare the current file with its latest backup file
          (dired-backup-diff).  If the current file is itself a backup, compare
          it with the file it is a backup of; this way, you can compare a file
          with any backup version of your choice.

          The backup file is the first file given to diff.


ΓòÉΓòÉΓòÉ 31.10. Subdirectories in Dired ΓòÉΓòÉΓòÉ

 A Dired buffer displays just one directory in the normal case; but you can
optionally include its subdirectories as well.

 The simplest way to include multiple directories in one Dired buffer is to
specify the options `-lR' for running ls.  (If you give a numeric argument when
you run Dired, then you can specify these options in the minibuffer.)  That
produces a recursive directory listing showing all subdirectories at all
levels.

 But usually all the subdirectories are too many; usually you will prefer to
include specific subdirectories only.  You can do this with the i command:

i
          Insert the contents of a subdirectory later in the buffer.

          Use the i (dired-maybe-insert-subdir) command on a line that
          describes a file which is a directory.  It inserts the contents of
          that directory into the same Dired buffer, and moves there.  Inserted
          subdirectory contents follow the top-level directory of the Dired
          buffer, just as they do in `ls -lR' output.

          If the subdirectory's contents are already present in the buffer, the
          i command just moves to it.

          In either case, i sets the Emacs mark before moving, so C-x C-x takes
          you back to the old position in the buffer (the line describing that
          subdirectory).

          Use the l command (dired-do-redisplay) to update the subdirectory's
          contents.  Use k to delete the subdirectory. See Dired Updating.


ΓòÉΓòÉΓòÉ 31.11. Moving Over Subdirectories ΓòÉΓòÉΓòÉ

 When a Dired buffer lists subdirectories, you can use the page motion commands
C-x [ and C-x ] to move by entire directories.

 The following commands move across, up and down in the tree of directories
within one Dired buffer.  They move to directory header lines, which are the
lines that give a directory's name, at the beginning of the directory's
contents.

C-M-n
          Go to next subdirectory header line, regardless of level
          (dired-next-subdir).

C-M-p
          Go to previous subdirectory header line, regardless of level
          (dired-prev-subdir).

C-M-u
          Go up to the parent directory's header line (dired-tree-up).

C-M-d
          Go down in the directory tree, to the first subdirectory's header
          line (dired-tree-down).


ΓòÉΓòÉΓòÉ 31.12. Hiding Subdirectories ΓòÉΓòÉΓòÉ

 Hiding a subdirectory means to make it invisible, except for its header line,
via selective display (see Selective Display).

$
          Hide or reveal the subdirectory that point is in, and move point to
          the next subdirectory (dired-hide-subdir).  A numeric argument serves
          as a repeat count.

M-$
          Hide all subdirectories in this Dired buffer, leaving only their
          header lines (dired-hide-all).  Or, if any subdirectory is currently
          hidden, make all subdirectories visible again.  You can use this
          command to get an overview in very deep directory trees or to move
          quickly to subdirectories far away.

 Ordinary Dired commands never consider files inside a hidden subdirectory.
For example, the commands to operate on marked files ignore files in hidden
directories even if they are marked.  Thus you can use hiding to temporarily
exclude subdirectories from operations without having to remove the markers.

 The subdirectory hiding commands toggle; that is they unhide what was hidden
and vice versa.


ΓòÉΓòÉΓòÉ 31.13. Updating the Dired Buffer ΓòÉΓòÉΓòÉ

 This section describes commands to update the Dired buffer to reflect outside
(non-Dired) changes in the directories and files, and to delete part of the
Dired buffer.

g
          Update the entire contents of the Dired buffer (revert-buffer).

l
          Update the specified files (dired-do-redisplay).

k
          Delete the specified file lines---not the files, just the lines
          (dired-do-kill-lines).

 Type g (revert-buffer) to update the contents of the Dired buffer, based on
changes in the files and directories listed. This preserves all marks except
for those on files that have vanished. Hidden subdirectories are updated but
remain hidden.

 To update only some of the files, type l (dired-do-redisplay).  This command
applies to the next n files, or to the marked files if any, or to the current
file.  Updating them means reading their current status from the file system
and changing the buffer to reflect it properly.

 If you use l on a subdirectory header line, it updates the contents of the
corresponding subdirectory.

 To delete the specified file lines---not the files, just the lines---type k
(dired-do-kill-lines).  This command applies to the next n files, or to the
marked files if any, or to the current file.

 If you kill the line for a file that is a directory, the directory's contents
are also deleted from the buffer.  Typing C-u k on the header line for a
subdirectory is another way to delete a subdirectory from the Dired buffer.

 The g command brings back any individual lines that you have killed in this
way, but not subdirectories---you must use i to reinsert each subdirectory.


ΓòÉΓòÉΓòÉ 31.14. Dired and find ΓòÉΓòÉΓòÉ

 You can select a set of files for display in a Dired buffer more flexibly by
using the find utility to choose the files.

 To search for files with names matching a wildcard pattern use M-x
find-name-dired.  It reads arguments directory and pattern, and chooses all the
files in directory or its subdirectories whose individual names match pattern.

 The files thus chosen are displayed in a Dired buffer in which the ordinary
Dired commands are available.

 If you want to test the contents of files, rather than their names, use M-x
find-grep-dired.  This command reads two minibuffer arguments, directory and
regexp; it chooses all the files in directory or its subdirectories that
contain a match for regexp.  It works by running the programs find and grep.

 The most general command in this series is M-x find-dired, which lets you
specify any condition that find can test.  It takes two minibuffer arguments,
directory and find-args; it runs find in directory, passing find-args to tell
find what condition to test.  To use this command, you need to know how to use
find.


ΓòÉΓòÉΓòÉ 32. The Calendar and the Diary ΓòÉΓòÉΓòÉ

 Emacs provides the functions of a desk calendar, with a diary of planned or
past events.  To enter the calendar, type M-x calendar; this displays a
three-month calendar centered on the current month, with point on the current
date.  If you use prefix argument as in C-u M-x calendar, it prompts you for
the month and year to be the center of the three-month calendar.  The calendar
uses its own buffer and the major mode is Calendar mode.

 To exit the calendar, type q.


ΓòÉΓòÉΓòÉ 32.1. Movement in the Calendar ΓòÉΓòÉΓòÉ

 Calendar mode lets you move in logical units of time such as days, weeks,
months, and years.  If you move outside the three months originally displayed,
the calendar display scrolls automatically through time.  Moving to a date lets
you view its holidays or diary entries, convert it to other calendars; moving
longer time periods is useful simply to scroll the calendar.


ΓòÉΓòÉΓòÉ 32.1.1. Motion by Integral Days, Weeks, Months, Years ΓòÉΓòÉΓòÉ

 The commands for movement in the calendar buffer parallel the commands for
movement in text.  You can move forward and backward by days, weeks, months,
and years.

C-f
          Move point one day forward (calendar-forward-day).

C-b
          Move point one day backward (calendar-backward-day).

C-n
          Move point one week forward (calendar-forward-week).

C-p
          Move point one week backward (calendar-backward-week).

M-}
          Move point one month forward (calendar-forward-month).

M-{
          Move point one month backward (calendar-backward-month).

C-x ]
          Move point one year forward (calendar-forward-year).

C-x [
          Move point one year backward (calendar-forward-year).

 The day and week commands are natural analogues of the usual Emacs commands
for moving by characters and by lines.  Just as C-n usually moves to the same
column in the following line, in Calendar mode it moves to the same day in the
following week.  And C-p moves to the same day in the previous week.

 The arrow keys are equivalent to C-f, C-b, C-n and C-p, just as they normally
are in other modes.

 The commands for motion by months and years work like those for weeks, but
move a larger distance.  The month commands M-} and M-{ move forward or
backward by an entire month's time.  The year commands C-x ] and C-x [ move
forward or backward a whole year.

 The easiest way to remember these commands is to consider months and years
analogous to paragraphs and pages of text, respectively.  But the commands
themselves are not quite analogous.  The ordinary Emacs paragraph commands move
to the beginning or end of a paragraph, whereas these month and year commands
move by an entire month or an entire year, which usually involves skipping
across the end of a month or year.

 All these commands accept a numeric argument as a repeat count. For
convenience, the digit keys and the minus sign specify numeric arguments in
Calendar mode even without the Meta modifier.  For example, 100 C-f moves point
100 days forward from its present location.


ΓòÉΓòÉΓòÉ 32.1.2. Beginning or End of Week, Month or Year ΓòÉΓòÉΓòÉ

 A week (or month, or year) is not just a quantity of days; we think of new
weeks (months, years) as starting on particular days.  So Calendar mode
provides commands to move to the beginning or end of a week, month or year:

C-a
          Move point to beginning of week (calendar-beginning-of-week).

C-e
          Move point to end of week (calendar-end-of-week).

M-a
          Move point to beginning of month (calendar-beginning-of-month).

M-e
          Move point to end of month (calendar-end-of-month).

M-<
          Move point to beginning of year (calendar-beginning-of-year).

M->
          Move point to end of year (calendar-end-of-year).

 These commands also take numeric arguments as repeat counts, with the repeat
count indicating how many weeks, months, or years to move backward or forward.


ΓòÉΓòÉΓòÉ 32.1.3. Particular Dates ΓòÉΓòÉΓòÉ

 Calendar mode provides commands for getting to a particular date specified
absolutely.

g d
          Move point to specified date (calendar-goto-date).

o
          Center calendar around specified month (calendar-other-month).

.
          Move point to today's date (calendar-current-month).

 g d (calendar-goto-date) prompts for a year, a month, and a day of the month,
and then moves to that date.  Because the calendar includes all dates from the
beginning of the current era, you must type the year in its entirety; that is,
type `1990', not `90'.

 o (calendar-other-month) prompts for a month and year, then centers the
three-month calendar around that month.

 You can return to today's date with . (calendar-current-month).


ΓòÉΓòÉΓòÉ 32.2. Scrolling in the Calendar ΓòÉΓòÉΓòÉ

 The calendar display scrolls automatically through time when you move out of
the visible portion.  You can also scroll it manually.  Imagine that the
calendar window contains a long strip of paper with the months on it. Scrolling
it means moving the strip so that new months become visible in the window.

C-x <
          Scroll calendar one month forward (scroll-calendar-left).

C-x >
          Scroll calendar one month backward (scroll-calendar-right).

C-v
NEXT
          Scroll calendar three months forward
          (scroll-calendar-left-three-months).

M-v
PRIOR
          Scroll calendar three months backward
          (scroll-calendar-right-three-months).

SPC
          Scroll the next window (scroll-other-window).

 The most basic calendar scroll commands scroll by one month at a time.  This
means that there are two months of overlap between the display before the
command and the display after.  C-x < scrolls the calendar contents one month
to the left; that is, it moves the display forward in time.  C-x > scrolls the
contents to the right, which moves backwards in time.

 The commands C-v and M-v scroll the calendar by an entire
``screenful''---three months---in analogy with the usual meaning of these
commands.  C-v makes later dates visible and M-v makes earlier dates visible.
These commands take a numeric argument as a repeat count; in particular, since
C-u (universal-argument) multiplies the next command by four, typing C-u C-v
scrolls the calendar forward by a year and typing C-u M-v scrolls the calendar
backward by a year.

 The function keys NEXT and PRIOR are equivalent to C-v and M-v, just as they
are in other modes.

 In Calendar mode, you can use SPC (scroll-other-window) to scroll the other
window.  This is handy when you display a list of holidays or diary entries in
another window.


ΓòÉΓòÉΓòÉ 32.3. Counting Days ΓòÉΓòÉΓòÉ

M-=
          Display the number of days in the current region
          (calendar-count-days-region).

 To determine the number of days in the region, type M-=
(calendar-count-days-region).  The numbers of days printed is inclusive; that
is, it includes the days specified by mark and point.


ΓòÉΓòÉΓòÉ 32.4. Miscellaneous Calendar Commands ΓòÉΓòÉΓòÉ

p d
          Display day-in-year (calendar-print-day-of-year).

C-c C-l
          Regenerate the calendar window (redraw-calendar).

q
          Exit from calendar (exit-calendar).

 To print the number of days elapsed since the start of the year, or the number
of days remaining in the year, type the p d command
(calendar-print-day-of-year).  This displays both of those numbers in the echo
area.  The number of days elapsed includes the selected date.  The number of
days remaining does not include that date.

 If the calendar window gets corrupted, type C-c C-l (redraw-calendar) to
redraw it.

 To exit from the calendar, type q (exit-calendar).  This buries all buffers
related to the calendar and returns the window display to what it was when you
entered the calendar.


ΓòÉΓòÉΓòÉ 32.5. Holidays ΓòÉΓòÉΓòÉ

 The Emacs calendar knows about all major and many minor holidays, and can
display them.

h
          Display holidays for the selected date (calendar-cursor-holidays).

x
          Mark holidays in the calendar window (mark-calendar-holidays).

u
          Unmark calendar window (calendar-unmark).

a
          List all holidays for the displayed three months in another window
          (list-calendar-holidays).

M-x holidays
          List all holidays for three months around today's date in another
          window.

 To see if any holidays fall on a given date, position point on that date in
the calendar window and use the h command.  This names the holidays for that
date, in the echo area if they fit there, otherwise in a separate window.

 To find the distribution of holidays for a wider period, use the x command.
This displays a `*' after each date on which a holiday falls.  The command
applies both to the currently visible months and to other months that
subsequently become visible by scrolling.  To turn marking off and erase the
current marks, type u, which also erases any diary marks (see Diary).

 To get even more detailed information, use the a command, which displays a
separate buffer containing a list of all holidays in the current three-month
range.

 The command M-x holidays displays the list of holidays for the current month
and the preceding and succeeding months; this works even if you don't have a
calendar window.  If you want the list of holidays centered around a different
month, use C-u M-x holidays, which prompts for the month and year.

 The holidays known to Emacs include American holidays and the major Christian,
Jewish, and Islamic holidays; when floating point is available, the calendar
also knows about solstices and equinoxes.

 The dates used by Emacs for holidays are based on current practice, not
historical fact.  Historically, for instance, the start of daylight savings
time and even its existence have varied from year to year, but present American
law mandates that daylight savings time begins on the first Sunday in April.
Emacs always uses this definition, even though it is wrong for some prior
years.


ΓòÉΓòÉΓòÉ 32.6. Times of Sunrise and Sunset ΓòÉΓòÉΓòÉ

 Emacs can tell you, to within a minute or two, the times of sunrise and sunset
for any date, if floating point is available.

S
          Display times of sunrise and sunset for the selected date
          (calendar-sunrise-sunset).

M-x sunrise-sunset
          Display times of sunrise and sunset for today's date.

C-u M-x sunrise-sunset
          Display times of sunrise and sunset for a specified date.

 Within the calendar, to display the local times of sunrise and sunset in the
echo area, move point to the date you want, and type S.

 The command M-x sunrise-sunset is available outside the calendar to print this
information for today's date or a specified date.  To specify a date other than
today, use C-u M-x sunrise-sunset, which prompts for the year, month, and day.

 Because the times of sunrise and sunset depend on the location on earth, you
need to tell Emacs your latitude, longitude, and location name before using
these commands.  Here is an example of what to set:

(setq calendar-latitude 40.1)
(setq calendar-longitude -88.2)
(setq calendar-location-name "Urbana, IL")

Use one decimal place in the values of calendar-latitude and
calendar-longitude.

 Your time zone also affects the local time of sunrise and sunset. Emacs
usually gets this information from the operating system, but if these values
are not what you want (or if the operating system does not supply them), you
must set them yourself.  Here is an example:

(setq calendar-time-zone -360)
(setq calendar-standard-time-zone-name "CST")
(setq calendar-daylight-time-zone-name "CDT")

The value of calendar-time-zone is the number of minutes difference between
your local standard time and Coordinated Universal Time (Greenwich time).  The
values of calendar-standard-time-zone-name and calendar-daylight-time-zone-name
are the abbreviations used in your time zone.

 Emacs displays the times of sunrise and sunset corrected for daylight savings
time.  The default rule for the starting and stopping dates of daylight savings
time is the American rule. See Daylight Savings, for how to specify a different
rule.

 You can display the times of sunrise and sunset for any location and any date
with C-u C-u M-x sunrise-sunset.  This asks you for a longitude, latitude,
number of minutes difference from Coordinated Universal Time, and date, and
then tells you the times of sunrise and sunset for that location on that date.


ΓòÉΓòÉΓòÉ 32.7. Phases of the Moon ΓòÉΓòÉΓòÉ

 Emacs can tell you the dates and times of the phases of the moon (new moon,
first quarter, full moon, last quarter), if floating point is available.  This
feature is useful for debugging problems that ``depend on the phase of the
moon.''

M
          Display the dates and times for all the quarters of the moon for the
          three-month period shown (calendar-phases-of-moon).

M-x phases-of-moon
          Display dates and times of the quarters of the moon for three months
          around today's date.

 Within the calendar, use the M command to display a separate buffer of the
phases of the moon for the current three-month range.  The dates and times
listed are accurate to within a few minutes.

 Outside the calendar, use the command M-x phases-of-moon to display the list
of the phases of the moon for the current month and the preceding and
succeeding months.  For information about a different month, use C-u M-x
phases-of-moon, which prompts for the month and year.

 The dates and times given for the phases of the moon are given in local time
(corrected for daylight savings, when appropriate); but if the variable
calendar-time-zone is void, Coordinated Universal Time (the Greenwich time
zone) is used.  See Daylight Savings.


ΓòÉΓòÉΓòÉ 32.8. Conversion To and From Other Calendars ΓòÉΓòÉΓòÉ

 The Emacs calendar displayed is always the Gregorian calendar, sometimes
called the ``new style'' calendar, which is used in most of the world today.
However, this calendar did not exist before the sixteenth century and was not
widely used before the eighteenth century; it did not fully displace the Julian
calendar and gain universal acceptance until the early twentieth century.  The
Emacs calendar can display any month since January, year 1 of the current era,
but the calendar displayed is the Gregorian, even for a date at which the
Gregorian calendar did not exist.

 While Emacs cannot display other calendars, it can convert dates to and from
several other calendars.


ΓòÉΓòÉΓòÉ 32.8.1. Supported Calendar Systems ΓòÉΓòÉΓòÉ

 The ISO commercial calendar is used largely in Europe.

 The Julian calendar, named after Julius Caesar, was the one used in Europe
throughout medieval times, and in many countries up until the nineteenth
century.

 Astronomers use a simple counting of days elapsed since noon, Monday, January
1, 4713 B.C. on the Julian calendar.  The number of days elapsed is called the
Julian day number or the Astronomical day number.

 The Hebrew calendar is the one used to determine the dates of Jewish holidays.
Hebrew calendar dates begin and end at sunset.

 The Islamic (Moslem) calendar is the one used to determine the dates of Moslem
holidays.  There is no universal agreement in the Islamic world about the
calendar; Emacs uses a widely accepted version, but the precise dates of
Islamic holidays often depend on proclamation by religious authorities, not on
calculations.  As a consequence, the actual dates of occurrence can vary
slightly from the dates computed by Emacs.  Islamic calendar dates begin and
end at sunset.

 The French Revolutionary calendar was created by the Jacobins after the 1789
revolution, to represent a more secular and nature-based view of the annual
cycle, and to install a 10-day week in a rationalization measure similar to the
metric system.  The French government officially abandoned this calendar at the
end of 1805.

 The Maya of Central America used three separate, overlapping calendar systems,
the long count, the tzolkin, and the haab. Emacs knows about all three of these
calendars.  Experts dispute the exact correlation between the Mayan calendar
and our calendar; Emacs uses the Goodman-Martinez-Thompson correlation in its
calculations.


ΓòÉΓòÉΓòÉ 32.8.2. Converting To Other Calendars ΓòÉΓòÉΓòÉ

 The following commands describe the selected date (the date at point) in
various other calendar systems:

p c
          Display ISO commercial calendar equivalent for selected day
          (calendar-print-iso-date).

p j
          Display Julian date for selected day (calendar-print-julian-date).

p a
          Display astronomical (Julian) day number for selected day
          (calendar-print-astro-day-number).

p h
          Display Hebrew date for selected day (calendar-print-hebrew-date).

p i
          Display Islamic date for selected day (calendar-print-islamic-date).

p f
          Display French Revolutionary date for selected day
          (calendar-print-french-date).

p m
          Display Mayan date for selected day (calendar-print-mayan-date).

 Put point on the desired date of the Gregorian calendar, then type the
appropriate keys.  The p is a mnemonic for ``print'' since Emacs ``prints'' the
equivalent date in the echo area.


ΓòÉΓòÉΓòÉ 32.8.3. Converting From Other Calendars ΓòÉΓòÉΓòÉ

 You can move to dates that you specify on the Commercial, Julian,
astronomical, Hebrew, Islamic, or French calendars:

g c
          Move to a date specified in the ISO commercial calendar
          (calendar-goto-iso-date).

g j
          Move to a date specified in the Julian calendar
          (calendar-goto-julian-date).

g a
          Move to a date specified in astronomical (Julian) day number
          (calendar-goto-astro-day-number).

g h
          Move to a date specified in the Hebrew calendar
          (calendar-goto-hebrew-date).

g i
          Move to a date specified in the Islamic calendar
          (calendar-goto-islamic-date).

g f
          Move to a date specified in the French Revolutionary calendar
          (calendar-goto-french-date).

 These commands ask you for a date on the other calendar, move point to the
Gregorian calendar date equivalent to that date, and display the other
calendar's date in the echo area.  Emacs uses strict completion (see
Completion) whenever it asks you to type a month name, so you don't have to
worry about the spelling of Hebrew, Islamic, or French names.

 One common question concerning the Hebrew calendar is the computation of the
anniversary of a date of death, called a ``yahrzeit.''  The Emacs calendar
includes a facility for such calculations.  If you are in the calendar, the
command M-x list-yahrzeit-dates asks you for a range of years and then displays
a list of the yahrzeit dates for those years for the date given by point.  If
you are not in the calendar, this command first asks you for the date of death
and the range of years, and then displays the list of yahrzeit dates.


ΓòÉΓòÉΓòÉ 32.8.4. Converting from the Mayan Calendar ΓòÉΓòÉΓòÉ

 Here are the commands to select dates based on the Mayan calendar:

g m l
          Move to a date specified by the long count calendar
          (calendar-goto-mayan-long-count-date).

g m p t
          Move to the previous occurrence of a place in the tzolkin calendar
          (calendar-previous-tzolkin-date).

g m n t
          Move to the next occurrence of a place in the tzolkin calendar
          (calendar-next-tzolkin-date).

g m p h
          Move to the previous occurrence of a place in the haab calendar
          (calendar-previous-haab-date).

g m n h
          Move to the next occurrence of a place in the haab calendar
          (calendar-next-haab-date).

g m p c
          Move to the previous occurrence of a place in the calendar round
          (calendar-previous-calendar-round-date).

g m n c
          Move to the next occurrence of a place in the calendar round
          (calendar-next-calendar-round-date).

 To understand these commands, you need to understand the Mayan calendars. The
long count is a counting of days with these units:

1 kin = 1 day@ @ @ 1 uinal = 20 kin@ @ @ 1 tun = 18 uinal
1 katun = 20 tun@ @ @ 1 baktun = 20 katun

Thus, the long count date 12.16.11.16.6 means 12 baktun, 16 katun, 11 tun, 16
uinal, and 6 kin.  The Emacs calendar can handle Mayan long count dates as
early as 7.17.18.13.1, but no earlier.  When you use the g m l command, type
the Mayan long count date with the baktun, katun, tun, uinal, and kin separated
by periods.

 The Mayan tzolkin calendar is a cycle of 260 days formed by a pair of
independent cycles of 13 and 20 days.  Since this cycle repeats endlessly,
Emacs provides commands to move backward and forward to the previous or next
point in the cycle.  Type g m p t to go to the previous tzolkin date; Emacs
asks you for a tzolkin date and moves point to the previous occurrence of that
date.  Similarly, type g m n t to go to the next occurrence of a tzolkin date.

 The Mayan haab calendar is a cycle of 365 days arranged as 18 months of 20
days each, followed a 5-day monthless period.  Like the tzolkin cycle, this
cycle repeats endlessly, and there are commands to move backward and forward to
the previous or next point in the cycle.  Type g m p h to go to the previous
haab date; Emacs asks you for a haab date and moves point to the previous
occurrence of that date. Similarly, type g m n h to go to the next occurrence
of a haab date.

 The Maya also used the combination of the tzolkin date and the haab date.
This combination is a cycle of about 52 years called a calendar round.  If you
type g m p c, Emacs asks you for both a haab and a tzolkin date and then moves
point to the previous occurrence of that combination.  Use g m p c to move
point to the next occurrence of a combination.  Emacs signals an error if the
haab/tzolkin date you have typed is impossible.

 Emacs uses strict completion (see Completion) whenever it asks you to type a
Mayan name, so you don't have to worry about spelling.


ΓòÉΓòÉΓòÉ 32.9. The Diary ΓòÉΓòÉΓòÉ

 The Emacs diary keeps track of appointments or other events on a daily basis,
in conjunction with the calendar.  To use the diary feature, you must first
create a diary file containing a list of events and their dates.  Then Emacs
can automatically pick out and display the events for today, for the immediate
future, or for any specified date.

 By default, Emacs uses `~/diary' as the diary file.  This is the same file
that the calendar utility uses.  A sample `~/diary' file is:

12/22/1988 Twentieth wedding anniversary!!
&1/1. Happy New Year!
10/22 Ruth's birthday.
* 21, *: Payday
Tuesday--weekly meeting with grad students at 10am
         Supowit, Shen, Bitner, and Kapoor to attend.
1/13/89 Friday the thirteenth!!
&thu 4pm squash game with Lloyd.
mar 16 Dad's birthday
April 15, 1989 Income tax due.
&* 15 time cards due.

 Although you probably will start by creating a diary manually, Emacs provides
a number of commands to let you view, add, and change diary entries.


ΓòÉΓòÉΓòÉ 32.9.1. Commands Displaying Diary Entries ΓòÉΓòÉΓòÉ

 Once you have created a `~/diary' file, you can view it from within the
calendar.  You can also view today's events outside of Calendar mode.

d
          Display any diary entries for the selected date (view-diary-entries).

s
          Display entire diary file (show-all-diary-entries).

m
          Mark all visible dates that have diary entries (mark-diary-entries).

u
          Unmark calendar window (calendar-unmark).

M-x print-diary-entries
          Print hard copy of the diary display as it appears.

M-x diary
          Display any diary entries for today's date.

 Displaying the diary entries with d shows in a separate window the diary
entries for the selected date in the calendar.  The mode line of the new window
shows the date of the diary entries and any holidays that fall on that date.

 If you specify a numeric argument with d, it shows all the diary entries for
that many successive days.  Thus, 2 d displays all the entries for the selected
date and for the following day.

 To get a broader view of which days are mentioned in the diary, use the m
command.  This places a `+' after each date which has a diary entry.  The
command applies both to the currently visible months and to other months that
subsequently become visible by scrolling.  To turn marking off and erase the
current marks, type u, which also turns off holiday marks (see Holidays).

 To see the full diary file, rather than just some of the entries, use the s
command.

 Display of selected diary entries uses the selective display feature to hide
entries that don't apply.  This is the same feature that Outline mode uses to
show part of an outline (see Outline Mode).  The diary buffer as you see it is
an illusion, so simply printing the buffer does not print what you see on your
screen.

  There is a special command to print hard copy of the diary buffer as it
appears; this command is M-x print-diary-entries.  It sends the data directly
to the printer.  You can customize it like lpr-region (see Hardcopy).

 The command M-x diary displays the diary entries for the current date,
independently of the calendar display, and optionally for the next few days as
well; the variable number-of-diary-entries specifies how many days to include.
See Calendar/Diary Options.

 If you put (diary) in your `.emacs' file, this automatically displays a window
with the day's diary entries, when you enter Emacs.  The mode line of the
displayed window shows the date and any holidays that fall on that date.


ΓòÉΓòÉΓòÉ 32.9.2. The Diary File ΓòÉΓòÉΓòÉ

 Your diary file is a file that records events associated with particular
dates.  The name of the diary file is specified by the variable diary-file;
`~/diary' is the default.  You can use the same file for the calendar utility
program, since its formats are a subset of the ones allowed by the Emacs diary
facilities.

 Each entry in the diary file describes one event and consists of one or more
lines.  An entry always begins with a date specification at the left margin.
The rest of the entry is simply text to describe the event.  If the entry has
more than one line, then the lines after the first must begin with whitespace
to indicate they continue a previous entry.  Lines that do not begin with valid
dates and do not continue a preceding entry are ignored.

 You can inhibit the marking of certain diary entries in the calendar window;
to do this, insert an ampersand (`&') at the beginning of the entry, before the
date.  This has no effect on display of the entry in the diary window; it
affects only marks on dates in the calendar window.  Nonmarking entries are
especially useful for generic entries that would otherwise mark many different
dates.

 If the first line of a diary entry consists only of the date or day name with
no following blanks or punctuation, then the diary window display doesn't
include that line; only the continuation lines appear. For example:

02/11/1989
      Bill B. visits Princeton today
      2pm Cognitive Studies Committee meeting
      2:30-5:30 Liz at Lawrenceville
      4:00pm Dentist appt
      7:30pm Dinner at George's
      8:00-10:00pm concert

appears in the diary window without the date line at the beginning. This style
of entry looks neater when you display just a single day's entries, but can
cause confusion if you ask for more than one day's entries.

 You can edit the diary entries as they appear in the window, but it is
important to remember that the buffer displayed contains the entire diary file,
with portions of it concealed from view.  This means, for instance, that the
C-f (forward-char) command can put point at what appears to be the end of the
line, but what is in reality the middle of some concealed line.

 Be careful when editing the diary entries!  Inserting additional lines or
adding/deleting characters in the middle of a visible line cannot cause
problems, but editing at the end of a line may not do what you expect.
Deleting a line may delete other invisible entries that follow it.  Before
editing the diary, it is best to display the entire file with s
(show-all-diary-entries).


ΓòÉΓòÉΓòÉ 32.9.3. Date Formats ΓòÉΓòÉΓòÉ

 Here are some sample diary entries, illustrating different ways of formatting
a date.  The examples all show dates in American order (month, day, year), but
Calendar mode supports European order (day, month, year) as an option.

4/20/93  Switch-over to new tabulation system
apr. 25  Start tabulating annual results
4/30  Results for April are due
*/25  Monthly cycle finishes
Friday  Don't leave without backing up files

 The first entry appears only once, on April 20, 1993.  The second and third
appear every year on the specified dates, and the fourth uses a wildcard
(asterisk) for the month, so it appears on the 25th of every month.  The final
entry appears every week on Friday.

 You can use just numbers to express a date, as in `month/day' or
`month/day/year'.  This must be followed by a nondigit.  In the date itself,
month and day are numbers of one or two digits.  year is a number and may be
abbreviated to the last two digits; that is, you can use `11/12/1989' or
`11/12/89'.

 Dates can also have the form `monthname day' or `monthname day, year', where
the month's name can be spelled in full or abbreviated to three characters
(with or without a period).  Case is not significant.

 A date may be generic, or partially unspecified.  Then the entry applies to
all dates that match the specification.  If the date does not contain a year,
it is generic and applies to any year.  Alternatively, month, day, or year can
be a `*'; this matches any month, day, or year, respectively.  Thus, a diary
entry `3/*/*' matches any day in March of any year; so does `march *'.

 If you prefer the European style of writing dates---in which the day comes
before the month---type M-x european-calendar while in the calendar, or set the
variable european-calendar-style to t before using any calendar or diary
command.  This mode interprets all dates in the diary in the European manner,
and also uses European style for displaying diary dates.  (Note that there is
no comma after the monthname in the European style.)  To go back to the
(default) American style of writing dates, type M-x american-calendar.

 You can use the name of a day of the week as a generic date which applies to
any date falling on that day of the week.  You can abbreviate the day of the
week to three letters (with or without a period) or spell it in full; case is
not significant.


ΓòÉΓòÉΓòÉ 32.9.4. Commands to Add to the Diary ΓòÉΓòÉΓòÉ

 While in the calendar, there are several commands to create diary entries:

i d
          Add a diary entry for the selected date (insert-diary-entry).

i w
          Add a diary entry for the selected day of the week
          (insert-weekly-diary-entry).

i m
          Add a diary entry for the selected day of the month
          (insert-monthly-diary-entry).

i y
          Add a diary entry for the selected day of the year
          (insert-yearly-diary-entry).

 You can make a diary entry for a specific date by selecting that date in the
calendar window and typing the i d command.  This command displays the end of
your diary file in another window and inserts the date; you can then type the
rest of the diary entry.

 If you want to make a diary entry that applies to a specific day of the week,
select that day of the week (any occurrence will do) and type i w.  This
inserts the day-of-week as a generic date; you can then type the rest of the
diary entry.

 You can make a monthly diary entry in the same fashion.  Select the day of the
month, use the i m command, and type rest of the entry.  Similarly, you can
insert a yearly diary entry with the i y command.

 All of the above commands make marking diary entries.  If you want the diary
entry to be nonmarking, give a prefix argument to the command. For example, C-u
i w makes a nonmarking, weekly diary entry.

 When you modify the diary file, be sure to save the file before exiting Emacs.


ΓòÉΓòÉΓòÉ 32.9.5. Special Diary Entries ΓòÉΓòÉΓòÉ

 In addition to entries based on calendar dates, your diary file can contain
special entries for regular events such as anniversaries. These entries are
based on Lisp expressions (sexps) that Emacs evaluates as it scans the diary
file.  Instead of a date, a special entry contains `%%' followed by a Lisp
expression which must begin and end with parentheses.  The Lisp expression
determines which dates the entry applies to.

 Calendar mode provides commands to insert certain commonly used special
entries:

i a
          Add an anniversary diary entry for the selected date
          (insert-anniversary-diary-entry).

i b
          Add a block diary entry for the current region
          (insert-block-diary-entry).

i c
          Add a cyclic diary entry starting at the date
          (insert-cyclic-diary-entry).

 If you want to make a diary entry that applies to the anniversary of a
specific date, move point to that date and use the i a command. This displays
the end of your diary file in another window and inserts the anniversary
description; you can then type the rest of the diary entry.  The entry looks
like this:

%%(diary-anniversary 10 31 1948) Arthur's birthday

This entry applies to October 31 in any year after 1948; `10 31 1948' specifies
the date.  (If you are using the European calendar style, the month and day are
interchanged.)  The reason this expression requires a beginning year is that
advanced diary functions can use it to calculate the number of elapsed years.

 You can make a diary entry entry for a block of dates by setting the mark at
the date at one end of the block, moving point to the date at the other end of
the block, and using the i b command.  This command causes the end of your
diary file to be displayed in another window and the block description to be
inserted; you can then type the diary entry.  Here is a block diary entry that
applies to all dates from June 24, 1990 through July 10, 1990:

%%(diary-block 6 24 1990 7 10 1990) Vacation

The `6 24 1990' indicates the starting date and the `7 10 1990' indicates the
stopping date.  (Again, if you are using the European calendar style, the month
and day are interchanged.)

  Cyclic diary entries repeat after a fixed interval of days.  To create one,
select the starting date and use the i c command.  The command prompts for the
length of interval, then inserts the entry. It looks like this:

%%(diary-cyclic 50 3 1 1990) Renew medication

which applies to March 1, 1990 and every 50th day following; `3 1 1990'
specifies the starting date.  (If you are using the European calendar style,
the month and day are interchanged.)

 All three of the these commands make marking diary entries.  If you want the
diary entry to be nonmarking, give a numeric argument to the command.  For
example, C-u i a makes a nonmarking anniversary diary entry.

 Marking sexp diary entries in the calendar is extremely time-consuming, since
every date visible in the calendar window must be individually checked.  So
it's a good idea to make sexp diary entries nonmarking (with `&') when
possible.

 Another sophisticated kind of sexp entry, a floating diary entry, specifies a
regularly-occurring event by offsets specified in days, weeks, and months.  It
is comparable to a crontab entry interpreted by the cron utility.  Here is a
nonmarking, floating diary entry that applies to the last Thursday in November:

&%%(diary-float 11 4 -1) American Thanksgiving

The 11 specifies November (the eleventh month), the 4 specifies Thursday (the
fourth day of the week, where Sunday is numbered zero), and the -1 specifies
``last'' (1 would mean ``first'', 2 would mean ``second'', -2 would mean
``second-to-last'', and so on).  The month can be a single month or a list of
months.  Thus you could change the 11 above to `'(1 2 3)' and have the entry
apply to the last Thursday of January, February, and March.  If the month is t,
the entry applies to all months of the year.

 Most generally, special diary entries can perform arbitrary computations to
determine when they apply. See Sexp Diary Entries.


ΓòÉΓòÉΓòÉ 32.10. Appointments ΓòÉΓòÉΓòÉ

 If you have a diary entry for an appointment, and that diary entry begins with
a recognizable time of day, Emacs can warn you, several minutes beforehand,
that that appointment is pending.  Emacs alerts you to the appointment by
displaying a message in the mode line.

 To enable appointment notification, you must enable the time display feature
of Emacs, M-x display-time (see Mode Line).  You must also add the function
appt-make-list to the diary-display-hook, like this:

(add-hook 'diary-display-hook 'appt-make-list)

 With these preparations done, when you display the diary (either with the d
command in the calendar window or with the M-x diary command), it sets up an
appointment list of all the diary entries found with recognizable times of day,
and reminds you just before each of them.

 For example, if you the diary file contains these lines:

Monday
  9:30am Coffee break
 12:00pm Lunch

Then on Mondays, after you have displayed the diary, you will be reminded at
9:20am about your coffee break and at 11:50am about lunch.

 Diary entries can have the time in the conventional American style, or in
``military'' style.  You need not be consistent; your diary file can have a
mixture of the two styles.

 Emacs updates the appointments list automatically just after midnight.  This
also displays the next days' diary entries in the diary buffer, unless you set
appt-display-diary to nil.

 You can also use the appointment notification facility like an alarm clock.
The command M-x appt-add adds entries to the appointment list without affecting
your diary file.  You delete entries from the appointment list with M-x
appt-delete.

 You can turn off the appointment notification feature at any time by setting
appt-issue-message to nil.


ΓòÉΓòÉΓòÉ 32.11. Daylight Savings Time ΓòÉΓòÉΓòÉ

 Emacs understands the difference between standard time and daylight savings
time---the times given for sunrise, sunset, solstices, equinoxes, and the
phases of the moon take that into account.  The rules for daylight savings time
vary from place to place and have also varied historically from year to year.
To do the job properly, Emacs needs to know which rules to use.

 Some operating systems keep track of the rules that apply to the place where
you are; on these systems, Emacs gets the information it needs from the system
automatically.  If the system does not know the rules, you can tell Emacs the
rules to use by setting certain variables.

 If the system's data indicate that your area currently uses daylight savings
time, the default starting and stopping dates for daylight savings time are the
present-day American rules of the first Sunday in April until the last Sunday
in October.  If this isn't right, you can specify whatever rules you want by
setting calendar-daylight-savings-starts and calendar-daylight-savings-ends.
Their values should be Lisp expressions that refer to the variable year, and
evaluate to the Gregorian date on which daylight savings time starts or
(respectively) ends, in the form of a list (month day year). The values should
be nil if your area does not use daylight savings time.

 Emacs uses these expressions to determine the starting date of daylight
savings time for the holiday list and for correcting times of day in the solar
and lunar calculations.

 The default value of calendar-daylight-savings-starts is this,

(calendar-nth-named-day 1 0 4 year)

which computes the first 0th day (Sunday) of the fourth month (April) in the
year specified by year.  If daylight savings time were changed to start on
October 1, you would set calendar-daylight-savings-starts to this:

(list 10 1 year)

 If there is no daylight savings time at your location, or if you want all
times in standard time, set calendar-daylight-savings-starts and
calendar-daylight-savings-ends to nil.

 In some areas, the difference between daylight savings time and standard time
is not one hour.  If this is so in your location, set the variable
calendar-daylight-time-offset to the difference, measured in minutes.

 If the transition to or from daylight savings time does not take place at 2AM,
you can specify when it takes place by setting the variable
calendar-daylight-savings-switchover-time.  Its value is the number of minutes
after midnight of the time when the transition should occur.


ΓòÉΓòÉΓòÉ 32.12. GNUS ΓòÉΓòÉΓòÉ

 gnus is an Emacs subsystem for reading and responding to netnews.  You can use
gnus to browse through news groups, look at summaries of articles in specific
group, and read articles of interest.  You can respond to authors or write
replies to all the readers of a news group.

 This section introduces gnus and describes several basic features.  Full
documentation will appear elsewhere.

To start gnus, type M-x gnus RET.


ΓòÉΓòÉΓòÉ 32.12.1. GNUS's Three Buffers ΓòÉΓòÉΓòÉ

gnus creates and uses three Emacs buffers, each with its own particular purpose
and its own major mode.

The Newsgroup buffer contains a list of newsgroups.  This is the first buffer
that gnus displays when it starts up.  Normally the list contains only the
newsgroups to which you subscribe (which are listed in your `.newsrc' file) and
which contain unread articles.  Use this buffer to select a specific newsgroup.

The Summary buffer lists the articles in a single newsgroup, including their
subjects, their numbers, and who posted them.  gnus creates a Summary buffer
for a newsgroup when you select the group in the Newsgroup buffer.  Use this
buffer to select an article, and to move around in an article.

The Article buffer displays the text of an article.  You rarely need to select
this buffer because you can read the text while keeping the Summary buffer
selected.


ΓòÉΓòÉΓòÉ 32.12.2. When GNUS Starts Up ΓòÉΓòÉΓòÉ

At startup, gnus reads your `.newsrc' news initialization file and attempts to
communicate with the local news server, which is a repository of news articles.
The news server need not be the same computer you are logged in on.

If you start gnus and connect to the server, but do not see any newsgroups
listed in the Newsgroup buffer, type L to get a listing of all the newsgroups.
Then type u to unsubscribe from particular newsgroups.  (Move the cursor using
n and p or the usual Emacs commands.)

When you quit gnus with q, it automatically records in your `.newsrc'
initialization file the subscribed or unsubscribed status of all newsgroups,
except for groups you have ``killed''.  (You do not need to edit this file
yourself, but you may.)  When new newsgroups come into existence, gnus adds
them automatically.


ΓòÉΓòÉΓòÉ 32.12.3. Summary of GNUS Commands ΓòÉΓòÉΓòÉ

Reading news is a two step process:

 1. Choose a newsgroup in the Newsgroup buffer.

 2. Select articles from the Summary buffer.  Each article selected is
    displayed in the Article buffer in a large window, below the Summary buffer
    in its small window.

Each buffer has commands particular to it, but commands that do the same things
have similar keybindings.  Here are commands for the Newsgroup and Summary
buffers:

z
          In the Newsgroup buffer, suspend gnus.  You can return to gnus later
          by selecting the Newsgroup buffer and typing g to get newly arrived
          articles.

q
          In the Newsgroup buffer, update your `.newsrc' initialization file
          and quit gnus.

          In the Summary buffer, exit the current newsgroup and return to the
          Newsgroup buffer.  Thus, typing q twice quits gnus.

L
          In the Newsgroup buffer, list all the newsgroups available on your
          news server.  This may be a long list!

l
          In the Newsgroup buffer, list only the newsgroups to which you
          subscribe and which contain unread articles.

u
          In the Newsgroup buffer, unsubscribe from (or subscribe to) the
          newsgroup listed in the line that point is on.  When you quit gnus by
          typing q, gnus lists your subscribed-to newsgroups in your `.newsrc'
          file.  The next time you start gnus, you see only the newsgroups
          listed in your `.newsrc' file.

C-k
          In the Newsgroup buffer, ``kill'' the current line's
          newsgroup---don't show it in the Newsgroup buffer from now on.  This
          affects future GNUS sessions as well as the present session.

          When you quit gnus by typing q, gnus writes information in the file
          `.newsrc' describing all newsgroups except those you have ``killed.''

SPC
          In the Newsgroup buffer, select the group on the line under the
          cursor and display the first unread article in that group.

          In the Summary buffer,

   o Select the article on the line under the cursor if none is selected.

   o Scroll the text of the selected article (if there is one).

   o Select the next unread article if at the end of the current article.

          Thus, you can move through all the articles by repeatedly typing SPC.

DEL
          In the Newsgroup Buffer, move point to the previous newsgroup
          containing unread articles.

          In the Summary buffer, scroll the text of the article backwards.

n
          Move point to the next unread newsgroup, or select the next unread
          article.

p
          Move point to the previous unread newsgroup, or select the previous
          unread article.
          C-n

C-p
          Move point to the next or previous item, even if it is marked as
          read. This does not select the article or newsgroup on that line.

s
          In the Summary buffer, do an incremental search of the current text
          in the Article buffer, just as if you switched to the Article buffer
          and typed C-s.

M-s regexp RET
          In the Summary buffer, search forward for articles containing a match
          for regexp.

C-c C-s C-n
C-c C-s C-s
C-c C-s C-d
C-c C-s C-a
          In the Summary buffer, sort the list of articles by number, subject,
          date, or author.

C-M-n
C-M-p
          In the Summary buffer, read the next or previous article with the
          same subject as the current article.


ΓòÉΓòÉΓòÉ 32.13. Sorting Text ΓòÉΓòÉΓòÉ

 Emacs provides several commands for sorting text in the buffer.  All operate
on the contents of the region (the text between point and the mark).  They
divide the text of the region into many sort records, identify a sort key for
each record, and then reorder the records into the order determined by the sort
keys.  The records are ordered so that their keys are in alphabetical order,
or, for numeric sorting, in numeric order.  In alphabetic sorting, all upper
case letters `A' through `Z' come before lower case `a', in accord with the
ASCII character sequence.

 The various sort commands differ in how they divide the text into sort records
and in which part of each record is used as the sort key.  Most of the commands
make each line a separate sort record, but some commands use paragraphs or
pages as sort records.  Most of the sort commands use each entire sort record
as its own sort key, but some use only a portion of the record as the sort key.

M-x sort-lines
          Divide the region into lines, and sort by comparing the entire text
          of a line.  A prefix argument means sort into descending order.

M-x sort-paragraphs
          Divide the region into paragraphs, and sort by comparing the entire
          text of a paragraph (except for leading blank lines).  A prefix
          argument means sort into descending order.

M-x sort-pages
          Divide the region into pages, and sort by comparing the entire text
          of a page (except for leading blank lines).  A prefix argument means
          sort into descending order.

M-x sort-fields
          Divide the region into lines, and sort by comparing the contents of
          one field in each line.  Fields are defined as separated by
          whitespace, so the first run of consecutive non-whitespace characters
          in a line constitutes field 1, the second such run constitutes field
          2, etc.

          Specify which field to sort by with a numeric argument: 1 to sort by
          field 1, etc.  A negative argument means sort into descending order.
          Thus, minus 2 means sort by field 2 in reverse-alphabetical order.
          If several lines have identical contents in the field being sorted,
          they keep same relative order that they had in the original buffer.

M-x sort-numeric-fields
          Like M-x sort-fields except the specified field is converted to a
          number for each line, and the numbers are compared.  `10' comes
          before `2' when considered as text, but after it when considered as a
          number.

M-x sort-columns
          Like M-x sort-fields except that the text within each line used for
          comparison comes from a fixed range of columns.  See below for an
          explanation.

 For example, if the buffer contains this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
whether the file has changed on disk since it was last visited or
saved.  If it has, you are asked to confirm that you want to change
the buffer.

then applying M-x sort-lines to the entire buffer produces this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
whether the file has changed on disk since it was last visited or

where the upper case `O' sorts before all lower case letters.  If you use C-u 2
M-x sort-fields instead, you get this:

implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
On systems where clash detection (locking of files being edited) is
whether the file has changed on disk since it was last visited or

where the sort keys were `Emacs', `If', `buffer', `systems' and `the'.

 M-x sort-columns requires more explanation.  You specify the columns by
putting point at one of the columns and the mark at the other column.  Because
this means you cannot put point or the mark at the beginning of the first line
to sort, this command uses an unusual definition of `region': all of the line
point is in is considered part of the region, and so is all of the line the
mark is in.

 For example, to sort a table by information found in columns 10 to 15, you
could put the mark on column 10 in the first line of the table, and point on
column 15 in the last line of the table, and then run sort-columns.
Equivalently, you could run it with the mark on column 15 in the first line and
point on column 10 in the last line.

 This can be thought of as sorting the rectangle specified by point and the
mark, except that the text on each line to the left or right of the rectangle
moves along with the text inside the rectangle. See Rectangles.


ΓòÉΓòÉΓòÉ 32.14. Running Shell Commands from Emacs ΓòÉΓòÉΓòÉ

 Emacs has commands for passing single command lines to inferior shell
processes; it can also run a shell interactively with input and output to an
Emacs buffer `*shell*'.

M-!
          Run a specified shell command line and display the output
          (shell-command).

M-|
          Run a specified shell command line with region contents as input;
          optionally replace the region with the output
          (shell-command-on-region).

M-x shell
          Run a subshell with input and output through an Emacs buffer. You can
          then give commands interactively.


ΓòÉΓòÉΓòÉ 32.14.1. Single Shell Commands ΓòÉΓòÉΓòÉ

 M-! (shell-command) reads a line of text using the minibuffer executes it as a
shell command in a subshell made just for this command.  Standard input for the
command comes from the null device.  If the shell command produces any output,
the output goes into an Emacs buffer named `*Shell Command Output*', which is
displayed in another window but not selected.  A numeric argument, as in M-1
M-!, directs this command to insert any output into the current buffer.  In
that case, point is left before the output and the mark is set after the
output.

 If the shell command line ends in `&', it runs asynchronously.

 M-| (shell-command-on-region) is like M-! but passes the contents of the
region as input to the shell command, instead of no input.  If a numeric
argument is used, meaning insert output in the current buffer, then the old
region is deleted first and the output replaces it as the contents of the
region.

 Both M-! and M-| use shell-file-name to specify the shell to use.  This
variable is initialized based on your SHELL environment variable when Emacs is
started.  If the file name does not specify a directory, the directories in the
list exec-path are searched; this list is initialized based on the environment
variable PATH when Emacs is started.  Your `.emacs' file can override either or
both of these default initializations.

 With M-! and M-|, Emacs has to wait until the shell command completes.  To
stop waiting, type C-g to quit; that also kills the shell command.


ΓòÉΓòÉΓòÉ 32.14.2. Interactive Inferior Shell ΓòÉΓòÉΓòÉ

 To run a subshell interactively, putting its typescript in an Emacs buffer,
use M-x shell.  This creates (or reuses) a buffer named `*shell*' and runs a
subshell with input coming from and output going to that buffer.  That is to
say, any ``terminal output'' from the subshell goes into the buffer, advancing
point, and any ``terminal input'' for the subshell comes from text in the
buffer.  To give input to the subshell, go to the end of the buffer and type
the input, terminated by RET.

 Emacs does not wait for the subshell to do anything.  You can switch windows
or buffers and edit them while the shell is waiting, or while it is running a
command.  Output from the subshell waits until Emacs has time to process it;
this happens whenever Emacs is waiting for keyboard input or for time to
elapse.

 To make multiple subshells, rename the buffer `*shell*' to something different
using M-x rename-uniquely.  Then type M-x shell again to create a new buffer
`*shell*' with its own subshell.  If you rename this buffer as well, you can
create a third one, and so on.  All the subshells run independently and in
parallel.

 The file name used to load the subshell is the value of the variable
explicit-shell-file-name, if that is non-nil.  Otherwise, the environment
variable ESHELL is used, or the environment variable SHELL if there is no
ESHELL.  If the file name specified is relative, the directories in the list
exec-path are searched (see Single Shell).

 As soon as the subshell is started, it is sent as input the contents of the
file `~/.emacs_shellname', if that file exists, where shellname is the name of
the file that the shell was loaded from. For example, if you use bash, the file
sent to it is `~/.emacs_bash'.

 cd, pushd and popd commands given to the inferior shell are watched by Emacs
so it can keep the `*shell*' buffer's default directory the same as the shell's
working directory.  These commands are recognized syntactically by examining
lines of input that are sent.  If you use aliases for these commands, you can
tell Emacs to recognize them also.  For example, if the value of the variable
shell-pushd-regexp matches the beginning of a shell command line, that line is
regarded as a pushd command.  Change this variable when you add aliases for
`pushd'.  Likewise, shell-popd-regexp and shell-cd-regexp are used to recognize
commands with the meaning of `popd' and `cd'.  These commands are recognized
only at the beginning of a shell command line.

 If Emacs gets an error while trying to handle what it believes is a `cd',
`pushd' or `popd' command, it runs the hook shell-set-directory-error-hook (see
Hooks).

 If Emacs does not properly track changes in the current directory of the
subshell, use the command M-x dirs to ask the shell what its current directory
is.  This command works for shells that support the most common command syntax;
it may not work for unusual shells.


ΓòÉΓòÉΓòÉ 32.14.3. Shell Mode ΓòÉΓòÉΓòÉ

 The shell buffer uses Shell mode, which defines several special keys attached
to the C-c prefix.  They are chosen to resemble the usual editing and job
control characters present in shells that are not under Emacs, except that you
must type C-c first.  Here is a complete list of the special key bindings of
Shell mode:

RET
          At end of buffer send line as input; otherwise, copy current line to
          end of buffer and send it (comint-send-input).  When a line is
          copied, any text at the beginning of the line that matches the
          variable shell-prompt-pattern is left out; this variable's value
          should be a regexp string that matches the prompts that your shell
          uses.

TAB
          Complete the file name before point in the shell buffer
          (comint-dynamic-complete).

M-?
          Display temporarily a list of the possible completions of the file
          name before point in the shell buffer
          (comint-dynamic-list-completions).

C-a
          Move to the beginning of the line, but after the prompt if any
          (comint-bol).

C-d
          Either delete a character or send EOF (comint-delchar-or-maybe-eof).
          Typed at the end of the shell buffer, C-d sends EOF to the subshell.
          Typed at any other position in the buffer, C-d deletes a character as
          usual.

C-c C-u
          Kill all text pending at end of buffer to be sent as input
          (comint-kill-input).

C-c C-w
          Kill a word before point (backward-kill-word).

C-c C-c
          Interrupt the shell or its current subjob if any
          (comint-interrupt-subjob).

C-c C-z
          Stop the shell or its current subjob if any (comint-stop-subjob).

C-c C-\
          Send quit signal to the shell or its current subjob if any
          (comint-quit-subjob).

C-c C-o
          Kill the last batch of output from a shell command
          (comint-kill-output).  This is useful if a shell command spews out
          lots of output that just gets in the way.

C-c C-r
          Scroll to display the beginning of the last batch of output at the
          top of the window; also move the cursor there (comint-show-output).

M-x dirs
          Ask the shell what its current directory is, so that Emacs can agree
          with the shell.

M-x send-invisible RET text RET
          Send text as input to the shell, after reading it without echoing.
          This is useful when a shell command runs a program that asks for a
          password.

M-x comint-continue-subjob
          Continue the shell process.  This is useful if you accidentally
          suspend the shell process. (You should not suspend the shell process.
          Suspending a subjob of the shell is a completely different
          matter--that is normal practice, but you must use the shell to
          continue the subjob; this command won't do it.)


ΓòÉΓòÉΓòÉ 32.14.4. Shell Command History ΓòÉΓòÉΓòÉ

 Shell buffers support history commands much like the minibuffer history
commands.

M-p
          Fetch the next earlier old shell command.

M-n
          Fetch the next later old shell command.

M-r regexp RET
M-s regexp RET
          Search backwards or forwards for old shell commands that match
          regexp.

 Shell buffers provide a history of previously entered shell commands.  To
reuse shell commands from the history, use the editing commands M-p, M-n, M-r
and M-s.  These work just like the minibuffer history commands except that they
operate on the text at the end of the shell buffer, the text that typing RET
will send to the shell.

 M-p fetches an earlier shell command to the end of the shell buffer.
Successive use of M-p fetches successively earlier shell commands, each
replacing any text that was already present as potential shell input. M-n does
likewise except that it finds successively more recent shell commands from the
buffer.

 The history search commands M-r and M-s read a regular expression and search
through the history for a matching command.  Aside from the choice of which
command to fetch, they work just like M-p and M-r.  If you enter an empty
regexp, these commands reuse the same regexp used last time.

 When you find the previous input you want, you can resubmit it by typing RET,
or you can edit it first and then resubmit it if you wish.

 These commands get the text of previous shell commands from a special history
list, not from the shell buffer itself.  Thus, editing the shell buffer, or
even killing large parts of it, does not affect the history that these commands
access.


ΓòÉΓòÉΓòÉ 32.15. Narrowing ΓòÉΓòÉΓòÉ

 Narrowing means focusing in on some portion of the buffer, making the rest
temporarily inaccessible.  The portion which you can still get to is called the
accessible portion.  Cancelling the narrowing, and making the entire buffer
once again accessible, is called widening.  The amount of narrowing in effect
in a buffer at any time is called the buffer's restriction.

C-x n n
          Narrow down to between point and mark (narrow-to-region).

C-x n w
          Widen to make the entire buffer accessible again (widen).

C-x n p
          Narrow down to the current page (narrow-to-page).

 When you have narrowed down to a part of the buffer, that part appears to be
all there is.  You can't see the rest, you can't move into it (motion commands
won't go outside the accessible part), you can't change it in any way.
However, it is not gone, and if you save the file all the inaccessible text
will be saved.  In addition to sometimes making it easier to concentrate on a
single subroutine or paragraph by eliminating clutter, narrowing can be used to
restrict the range of operation of a replace command or repeating keyboard
macro.  The word `Narrow' appears in the mode line whenever narrowing is in
effect.

 The primary narrowing command is C-x n n (narrow-to-region). It sets the
current buffer's restrictions so that the text in the current region remains
accessible but all text before the region or after the region is invisible.
Point and mark do not change.

 Alternatively, use C-x n p (narrow-to-page) to narrow down to the current
page.  See Pages, for the definition of a page.

 The way to undo narrowing is to widen with C-x n w (widen). This makes all
text in the buffer accessible again.

 You can get information on what part of the buffer you are narrowed down to
using the C-x = command.  See Position Info.

 Because narrowing can easily confuse users who do not understand it,
narrow-to-region is normally a disabled command.  Attempting to use this
command asks for confirmation and gives you the option of enabling it; once you
enable the command, confirmation will no longer be required for it.  See
Disabling.


ΓòÉΓòÉΓòÉ 32.16. Hardcopy Output ΓòÉΓòÉΓòÉ

 The Emacs commands for making hardcopy let you print either an entire buffer
or just part of one, either with or without page headers. See also the hardcopy
commands of Dired (see Misc File Ops) and the diary (see Diary Commands).

M-x print-buffer
          Print hardcopy of current buffer using Unix command `print' (`lpr
          -p').  This makes page headings containing the file name and page
          number.

M-x lpr-buffer
          Print hardcopy of current buffer using Unix command `lpr'. This makes
          no page headings.

M-x print-region
          Like print-buffer but prints only the current region.

M-x lpr-region
          Like lpr-buffer but prints only the current region.

 All the hardcopy commands pass extra switches to the lpr program based on the
value of the variable lpr-switches.  Its value should be a list of strings,
each string an option starting with `-'.  For example, to use a printer named
`nearme', set lpr-switches like this:

(setq lpr-switches '("-Pnearme"))


ΓòÉΓòÉΓòÉ 32.17. Two-Column Editing ΓòÉΓòÉΓòÉ

 Two-column mode lets you conveniently edit two side-by-side columns of text.
It uses two side-by-side windows, each showing its own buffer.

 There are three ways to enter two-column mode:

C-x 6 2
          Enter two-column mode with the current buffer on the left, and on the
          right, a buffer whose name is based on the current buffer's name
          (tc-two-columns).  If the right-hand buffer doesn't already exist, it
          starts out empty; the current buffer's contents are not changed.

          This command is appropriate when the current buffer contains just one
          column and you want to add another column.

C-x 6 s
          Split the current buffer, which contains two-column text, into two
          buffers, and display them side by side (tc-split).  The current
          buffer becomes the left-hand buffer, but the text in the right-hand
          column is moved into the right-hand buffer.  The current column
          specifies the split point.  Splitting starts with the current line
          and continues to the end of the buffer.

          This command is appropriate when you have a buffer that already
          contains two-column text, and you wish to separate the columns
          temporarily.

C-x 6 b buffer RET
          Enter two-column mode using the current buffer as the left-hand
          buffer, and using buffer buffer as the right-hand buffer
          (tc-associate-buffer).

 C-x 6 s looks for a column separator which is a string that appears on each
line between the two columns.  You can specify the width of the separator with
a numeric argument to C-x 6 s; that many characters, before point, constitute
the separator string.  By default, the width is 1, so the column separator is
the character before point.

 When a line has the separator at the proper place, C-x 6 s puts the text after
the separator into the right-hand buffer, and deletes the separator.  Lines
that don't have the column separator at the proper place remain unsplit; they
stay in the left-hand buffer, and the right-hand buffer gets an empty line to
correspond.  (This is the way to write a line which ``spans both columns while
in two-column mode: write it in the left-hand buffer, and put an empty line in
the right-hand buffer.)

 It's not a good idea to use ordinary scrolling commands during two-column
editing, because that separates the two parts of each split line.  Instead, use
these special scroll commands:

C-x 6 SPC
          Scroll both buffers up, in lockstep (tc-scroll-up).

C-x 6 DEL
          Scroll both buffers down, in lockstep (tc-scroll-down).

C-x 6 C-l
          Recenter both buffers, in lockstep (tc-recenter).

 When you have edited both buffers as you wish, merge them with C-x 6 1
(tc-merge).  This copies the text from the right-hand buffer as a second column
in the other buffer.  To go back to two-column editing, use C-x 6 s.

 Use C-x 6 d to disassociate the two buffers, leaving each as it stands
(tc-dissociate).  If the other buffer, the one not current when you type C-x 6
d, is empty, C-x 6 d kills it.


ΓòÉΓòÉΓòÉ 32.18. Editing Binary Files ΓòÉΓòÉΓòÉ

 There is a special major mode for editing binary files: Hexl mode.  To use it,
use M-x hexl-find-file instead of C-x C-f to visit the file.  This command
converts the file's contents to hexadecimal and lets you edit the translation.
When you save the file, it is converted automatically back to binary.

 You can also use M-x hexl-mode to translate an existing buffer into hex.  This
is useful if you visit a file normally and then discover it is a binary file.

 Ordinary text characters overwrite in Hexl mode.  This is to reduce the risk
of accidentally spoiling the alignment of data in the file. There are special
commands for insertion.  Here is a list of the commands of Hexl mode:

C-M-d
          Insert a byte with a code typed in decimal.

C-M-o
          Insert a byte with a code typed in octal.

C-M-x
          Insert a byte with a code typed in hex.

C-x [
          Move to the beginning of a 1k-byte ``page''.

C-x ]
          Move to the end of a 1k-byte ``page''.

M-g
          Move to an address specified in hex.

M-j
          Move to an address specified in decimal.

C-c C-c
          Leave Hexl mode, going back to the major mode this buffer had before
          you invoked hexl-mode.


ΓòÉΓòÉΓòÉ 32.19. Using Emacs as a Server ΓòÉΓòÉΓòÉ

 Various programs such as mail can invoke your choice of editor to edit a
particular piece of text, such as a message that you are sending.  By
convention, these programs use the environment variable EDITOR to specify which
editor to run.  If you set EDITOR to `emacs', they invoke Emacs---but in an
inconvenient fashion, by starting a new, separate Emacs process.  This is
inconvenient because it takes time and because the new Emacs process doesn't
share the buffers in the existing Emacs process.

 You can arrange to use your existing Emacs process as the editor for programs
like mail by using the Emacs client and Emacs server programs.  Here is how.

 First, the preparation.  Within Emacs, call the function server-start.  (Your
`.emacs' file can do this automatically if you add the expression
(server-start) to it.)  Then, outside Emacs, set the EDITOR environment
variable to `emacsclient'.

 Then, whenever any program invokes your specified EDITOR program, the effect
is to send a message to your principal Emacs telling it to visit a file.
(That's what the program emacsclient does.) Emacs obeys silently; it does not
immediately switch to the new file's buffer.  When you want to do that, type
C-x # (server-edit).

 When you've finished editing that buffer, type C-x # again. This saves the
file and sends a message back to the emacsclient program telling it to exit.
The programs that use EDITOR wait for the ``editor'' (actually, emacsclient) to
exit.  C-x # also checks to see if any other files are pending for you to edit,
and selects the next one.

 You can switch to a server buffer manually if you wish; you don't have to
arrive at it with C-x #.  But C-x # is the only way to say that you are
``finished'' with one.

 While mail or another application is waiting for emacsclient to finish,
emacsclient does not read terminal input.  So the terminal that mail was using
is effectively blocked for the duration.  In order to edit with your principal
Emacs, you need to be able to use it without using that terminal.  There are
two ways to do this:

o Using a window system, run mail and the principal Emacs in two separate
  windows.  While mail is waiting for emacsclient, the window where it was
  running is blocked, but you can use Emacs by switching windows.

o Use Shell mode in Emacs to run the other program such as mail; then,
  emacsclient blocks only the subshell under Emacs; you can still use Emacs to
  edit the file.


ΓòÉΓòÉΓòÉ 32.20. Recursive Editing Levels ΓòÉΓòÉΓòÉ

 A recursive edit is a situation in which you are using Emacs commands to
perform arbitrary editing while in the middle of another Emacs command.  For
example, when you type C-r inside of a query-replace, you enter a recursive
edit in which you can change the current buffer.  On exiting from the recursive
edit, you go back to the query-replace.

 Exiting the recursive edit means returning to the unfinished command, which
continues execution.  To exit, type C-M-c (exit-recursive-edit).

 You can also abort the recursive edit.  This is like exiting, but also quits
the unfinished command immediately.  Use the command C-] (abort-recursive-edit)
for this.  See Quitting.

 The mode line shows you when you are in a recursive edit by displaying square
brackets around the parentheses that always surround the major and minor mode
names.  Every window's mode line shows this, in the same way, since being in a
recursive edit is true of Emacs as a whole rather than any particular window or
buffer.

 It is possible to be in recursive edits within recursive edits.  For example,
after typing C-r in a query-replace, you may type a command that enters the
debugger.  This begins a recursive editing level for the debugger, within the
recursive editing level for C-r. Mode lines display a pair of square brackets
for each recursive editing level currently in progress.

 Exiting the inner recursive edit (such as, with the debugger c command)
resumes the command running in the next level up.  When that command finishes,
you can then use C-M-c to exit another recursive editing level, and so on.
Exiting applies to the innermost level only. Aborting also gets out of only one
level of recursive edit; it returns immediately to the command level of the
previous recursive edit.  If you wish, you can then abort the next recursive
editing level.

 Alternatively, the command M-x top-level aborts all levels of recursive edits,
returning immediately to the top level command reader.

 The text being edited inside the recursive edit need not be the same text that
you were editing at top level.  It depends on what the recursive edit is for.
If the command that invokes the recursive edit selects a different buffer
first, that is the buffer you will edit recursively.  In any case, you can
switch buffers within the recursive edit in the normal manner (as long as the
buffer-switching keys have not been rebound).  You could probably do all the
rest of your editing inside the recursive edit, visiting files and all.  But
this could have surprising effects (such as stack overflow) from time to time.
So remember to exit or abort the recursive edit when you no longer need it.

 In general, we try to minimize the use of recursive editing levels in GNU
Emacs.  This is because they constrain you to ``go back'' in a particular
order--from the innermost level toward the top level.  When possible, we
present different activities in separate buffers.  Some commands switch to a
new major mode but provide a way to switch back. These approaches give you more
flexibility to go back to unfinished tasks in the order you choose.


ΓòÉΓòÉΓòÉ 32.21. Dissociated Press ΓòÉΓòÉΓòÉ

 M-x dissociated-press is a command for scrambling a file of text either word
by word or character by character.  Starting from a buffer of straight English,
it produces extremely amusing output.  The input comes from the current Emacs
buffer.  Dissociated Press writes its output in a buffer named
`*Dissociation*', and redisplays that buffer after every couple of lines
(approximately) to facilitate reading it.

 Dissociated Press asks every so often whether to continue operating. Answer n
to stop it.  You can also stop at any time by typing C-g.  The dissociation
output remains in the `*Dissociation*' buffer for you to copy elsewhere if you
wish.

 Dissociated Press operates by jumping at random from one point in the buffer
to another.  In order to produce plausible output rather than gibberish, it
insists on a certain amount of overlap between the end of one run of
consecutive words or characters and the start of the next. That is, if it has
just printed out `president' and then decides to jump to a different point in
the file, it might spot the `ent' in `pentagon' and continue from there,
producing `presidentagon'. (This dissociword actually appeared during the
Vietnam War, when it was very appropriate.)  Long sample texts produce the best
results.

 A positive argument to M-x dissociated-press tells it to operate character by
character, and specifies the number of overlap characters.  A negative argument
tells it to operate word by word and specifies the number of overlap words.  In
this mode, whole words are treated as the elements to be permuted, rather than
characters.  No argument is equivalent to an argument of two.  For your
againformation, the output goes only into the buffer `*Dissociation*'.  The
buffer you start with is not changed.

 Dissociated Press produces nearly the same results as a Markov chain based on
a frequency table constructed from the sample text.  It is, however, an
independent, ignoriginal invention.  Dissociated Press techniquitously copies
several consecutive characters from the sample between random choices, whereas
a Markov chain would choose randomly for each word or character.  This makes
for more plausible sounding results, and runs faster.

 It is a mustatement that too much use of Dissociated Press can be a
developediment to your real work.  Sometimes to the point of outragedy. And
keep dissociwords out of your documentation, if you want it to be well
userenced and properbose.  Have fun.  Your buggestions are welcome.


ΓòÉΓòÉΓòÉ 32.22. Other Amusements ΓòÉΓòÉΓòÉ

 If you are a little bit bored, you can try M-x hanoi.  If you are considerably
bored, give it a numeric argument.  If you are very very bored, try an argument
of 9.  Sit back and watch.

 If you want a little more personal involvement, try M-x gomoku, which plays
the game Go Moku with you.

 M-x blackbox and M-x mpuz are two kinds of puzzles. blackbox challenges you to
determine the location of objects inside a box by tomography.  mpuz displays a
multiplication puzzle with letters standing for digits in a code that you must
guess---to guess a value, type a letter and then the digit you think it stands
for.

 When you are frustrated, try the famous Eliza program.  Just do M-x doctor.
End each input by typing RET twice.

 When you are feeling strange, type M-x yow.


ΓòÉΓòÉΓòÉ 32.23. Emulation ΓòÉΓòÉΓòÉ

 GNU Emacs can be programmed to emulate (more or less) most other editors.
Standard facilities can emulate these:

EDT (DEC VMS editor)
          Turn on EDT emulation with M-x edt-emulation-on.  M-x
          edt-emulation-off restores normal Emacs command bindings.

          Most of the EDT emulation commands are keypad keys, and most standard
          Emacs key bindings are still available.  The EDT emulation rebindings
          are done in the global keymap, so there is no problem switching
          buffers or major modes while in EDT emulation.

Gosling Emacs
          To turn on emulation of Gosling Emacs (alias Unipress Emacs), type
          the command M-x set-gosmacs-bindings.  This redefines many keys,
          mostly on the C-x and ESC prefixes, to work as they do in Gosmacs.
          M-x set-gnu-bindings returns to normal GNU Emacs by rebinding the
          same keys to the definitions they had before you used M-x
          set-gosmacs-bindings.

vi (Berkeley Unix editor)
          Turn on vi emulation with M-x vi-mode.  This is a major mode that
          replaces the previously established major mode.  All of the vi
          commands that, in real vi, enter ``input'' mode are programmed in the
          Emacs emulator to return to the previous major mode.  Thus, ordinary
          Emacs serves as vi's ``input'' mode.

          Because vi emulation works through major modes, it does not work to
          switch buffers during emulation.  Return to normal Emacs first.

          If you plan to use vi emulation much, you probably want to bind a key
          to the vi-mode command.

vi (alternate emulator)
          Another vi emulator said to resemble real vi more thoroughly is
          invoked by M-x vip-mode.  ``Input'' mode in this emulator is changed
          from ordinary Emacs so you can use ESC to go back to emulated vi
          command mode.  To get from emulated vi command mode back to ordinary
          Emacs, type C-z.

          This emulation does not work through major modes, and it is possible
          to switch buffers in various ways within the emulator.  It is not so
          necessary to assign a key to the command vip-mode as it is with
          vi-mode because terminating insert mode does not use it.

          For full information, see the long comment at the beginning of the
          source file, which is `lisp/vip.el' in the Emacs distribution.

I am interested in hearing which vi emulator users prefer, as well as in
receiving more complete user documentation for either or both emulators.
Warning: loading both at once may cause name conflicts; no one has checked.


ΓòÉΓòÉΓòÉ 33. Customization ΓòÉΓòÉΓòÉ

 This chapter talks about various topics relevant to adapting the behavior of
Emacs in minor ways.  See The Emacs Lisp Reference Manual for how to make more
far-reaching changes.

 All kinds of customization affect only the particular Emacs job that you do
them in.  They are completely lost when you kill the Emacs job, and have no
effect on other Emacs jobs you may run at the same time or later.  The only way
an Emacs job can affect anything outside of it is by writing a file; in
particular, the only way to make a customization `permanent' is to put
something in your `.emacs' file or other appropriate file to do the
customization in each session.  See Init File.


ΓòÉΓòÉΓòÉ 33.1. Minor Modes ΓòÉΓòÉΓòÉ

 Minor modes are optional features which you can turn on or off.  For example,
Auto Fill mode is a minor mode in which SPC breaks lines between words as you
type.  All the minor modes are independent of each other and of the selected
major mode.  Most minor modes say in the mode line when they are on; for
example, `Fill' in the mode line means that Auto Fill mode is on.

 Append -mode to the name of a minor mode to get the name of a command function
that turns the mode on or off.  Thus, the command to enable or disable Auto
Fill mode is called M-x auto-fill-mode.  These commands are usually invoked
with M-x, but you can bind keys to them if you wish.  With no argument, the
function turns the mode on if it was off and off if it was on.  This is known
as toggling.  A positive argument always turns the mode on, and an explicit
zero argument or a negative argument always turns it off.

 Enabling or disabling some minor modes applies only to the current buffer;
each buffer is independent of the other buffers.  Therefore, you can enable the
mode in particular buffers and disable it in others.

 Auto Fill mode allows you to enter filled text without breaking lines
explicitly.  Emacs inserts newlines as necessary to prevent lines from becoming
too long.  See Filling.

 Outline minor mode provides the same facilities as the major mode called
Outline mode; but since it is a minor mode instead, you can combine it with any
major mode.  See Outline Mode.

 Overwrite mode causes ordinary printing characters to replace existing text
instead of shoving it over.  For example, if the point is in front of the `B'
in `FOOBAR', then in Overwrite mode typing a G changes it to `FOOGAR', instead
of making it `FOOGBAR' as usual.

 Auto Save mode causes the contents of a buffer to be saved periodically to
reduce the amount you will lose in case of a system crash.  See Auto Save.

 The following minor modes normally apply to all buffers at once. Since each is
enabled or disabled by the value of a variable, you can set them differently
for particular buffers, by explicitly making the corresponding variables local
in those buffers. See Locals.

 Abbrev mode allows you to define abbreviations that automatically expand as
you type them.  For example, `amd' might expand to `abbrev mode'.  See Abbrevs,
for full information.

 Line Number mode enables continuous display in the mode line of the line
number of point.  See Mode Line.

 Scroll Bar mode gives each window a scroll bar (see Scroll Bars). Menu Bar
mode gives each frame a menu bar (see Menu Bars).  Both of these modes are
enabled by default when you use the X Window System.

 In Transient Mark mode, every change in the buffer ``deactivates'' the mark,
so that commands that operate on the region will get an error. This means you
must either set the mark, or explicitly ``reactivate'' it, before each command
that uses the region.  The advantage of Transient Mark mode is that Emacs can
display the region highlighted (currently only when using X).  See Setting
Mark.


ΓòÉΓòÉΓòÉ 33.2. Variables ΓòÉΓòÉΓòÉ

 A variable is a Lisp symbol which has a value.  The symbol's name is also
called the name of the variable.  A variable name can contain any characters
that can appear in a file, but conventionally variable names consist of words
separated by hyphens.  A variable can have a documentation string which
describes what kind of value it should have and how the value will be used.

 Lisp allows any variable to have any kind of value, but most variables that
Emacs uses require a value of a certain type.  Often the value should always be
a string, or should always be a number.  Sometimes we say that a certain
feature is turned on if a variable is ``non-nil,'' meaning that if the
variable's value is nil, the feature is off, but the feature is on for any
other value.  The conventional value to use to turn on the feature---since you
have to pick one particular value when you set the variable---is t.

 Emacs uses many Lisp variables for internal recordkeeping, as any Lisp program
must, but the most interesting variables for you are the ones that exist for
the sake of customization.  Emacs does not (usually) change the values of these
variables; instead, you set the values, and thereby alter and control the
behavior of certain Emacs commands.  These variables are called options.  Most
options are documented in this manual, and appear in the Variable Index (see
Variable Index).

 One example of a variable which is an option is fill-column, which specifies
the position of the right margin (as a number of characters from the left
margin) to be used by the fill commands (see Filling).


ΓòÉΓòÉΓòÉ 33.2.1. Examining and Setting Variables ΓòÉΓòÉΓòÉ

C-h v var RET
          Print the value and documentation of variable var
          (describe-variable).

M-x set-variable RET var RET value RET
          Change the value of variable var to value.

 To examine the value of a single variable, use C-h v (describe-variable),
which reads a variable name using the minibuffer, with completion.  It prints
both the value and the documentation of the variable.  For example,

C-h v fill-column RET

prints something like this:

fill-column's value is 75

Documentation:
*Column beyond which automatic line-wrapping should happen.
Automatically becomes buffer-local when set in any fashion.

The star at the beginning of the documentation indicates that this variable is
an option.  C-h v is not restricted to options; it allows any variable name.

 The most convenient way to set a specific option is with M-x set-variable.
This reads the variable name with the minibuffer (with completion), and then
reads a Lisp expression for the new value using the minibuffer a second time.
For example,

M-x set-variable RET fill-column RET 75 RET

sets fill-column to 75.

 You can set any variable with a Lisp expression using the function setq.
Here's how to use it to set fill-column:

(setq fill-column 75)

 Setting variables, like all means of customizing Emacs except where explicitly
stated, affects only the current Emacs session.


ΓòÉΓòÉΓòÉ 33.2.2. Editing Variable Values ΓòÉΓòÉΓòÉ

These two functions make it easy to display all the user edit options and
change some of them.

M-x list-options
          Display a buffer listing names, values and documentation of all
          options.

M-x edit-options
          Change option values by editing a list of options.

 M-x list-options displays a list of all Emacs option variables, in an Emacs
buffer named `*List Options*'.  Each option is shown with its documentation and
its current value.  Here is what a portion of it might look like:

;; exec-path:
("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc")
*List of directories to search programs to run in subprocesses.
Each element is a string (directory name)
or nil (try the default directory).
;;
;; fill-column:
75
*Column beyond which automatic line-wrapping should happen.
Automatically becomes buffer-local when set in any fashion.
;;

 M-x edit-options goes one step further and immediately selects the `*List
Options*' buffer; this buffer uses the major mode Options mode, which provides
commands that allow you to point at an option and change its value:

s
          Set the variable point is in or near to a new value read using the
          minibuffer.

x
          Toggle the variable point is in or near: if the value was nil, it
          becomes t; otherwise it becomes nil.

1
          Set the variable point is in or near to t.

0
          Set the variable point is in or near to nil.

n
p
          Move to the next or previous variable.

 Any changes take effect immediately, and last until you exit from Emacs.


ΓòÉΓòÉΓòÉ 33.2.3. Hooks ΓòÉΓòÉΓòÉ

 A hook is a variable where you can store a function or functions to be called
on a particular occasion by an existing program.  Emacs provides a number of
hooks for the sake of customization.

 Most of the hooks in Emacs are normal hooks.  These variables contain lists of
functions to be called with no arguments.  The reason most hooks are normal
hooks is so that you can use them in a uniform way.  Every variable in Emacs
whose name ends in `-hook' is a normal hook.

 Most major modes run hooks as the last step of initialization.  This makes it
easy for a user to customize the behavior of the mode, by overriding the local
variable assignments already made by the mode.  But hooks may also be used in
other contexts.  For example, the hook suspend-hook runs just before Emacs
suspends itself (see Exiting).

 The recommended way to add a hook function to a normal hook is by calling
add-hook.  You can use any valid Lisp function as the hook function.  For
example, here's how to set up a hook to turn on Auto Fill mode when entering
Text mode and other modes based on Text mode:

(add-hook 'text-mode-hook 'turn-on-auto-fill)

 The next example shows how to use a hook to customize the indentation of C
code.  (People often have strong personal preferences for one format compared
to another.)  Here the hook function is an anonymous lambda expression.

(add-hook 'c-mode-hook
  (function (lambda ()
              (setq c-indent-level 4
                    c-argdecl-indent 0
                    c-label-offset -4
                    c-continued-statement-indent 0
                    c-brace-offset 0
                    comment-column 40))))

(setq c++-mode-hook c-mode-hook)

 It is best to design your hook functions so that the order in which they are
executed does not matter.  Any dependence on the order is ``asking for
trouble.''  However, the order is predictable: the most recently added hook
functions are executed first.


ΓòÉΓòÉΓòÉ 33.2.4. Local Variables ΓòÉΓòÉΓòÉ

M-x make-local-variable RET var RET
          Make variable var have a local value in the current buffer.

M-x kill-local-variable RET var RET
          Make variable var use its global value in the current buffer.

M-x make-variable-buffer-local RET var RET
          Mark variable var so that setting it will make it local to the buffer
          that is current at that time.

 Any variable can be made local to a specific Emacs buffer.  This means that
its value in that buffer is independent of its value in other buffers.  A few
variables are always local in every buffer.  Every other Emacs variable has a
global value which is in effect in all buffers that have not made the variable
local.

 M-x make-local-variable reads the name of a variable and makes it local to the
current buffer.  Further changes in this buffer will not affect others, and
further changes in the global value will not affect this buffer.

 M-x make-variable-buffer-local reads the name of a variable and changes the
future behavior of the variable so that it will become local automatically when
it is set.  More precisely, once a variable has been marked in this way, the
usual ways of setting the variable automatically do make-local-variable first.
We call such variables per-buffer variables.

 Major modes (see Major Modes) always make the variables they set local to the
buffer.  This is why changing major modes in one buffer has no effect on other
buffers.  Minor modes also work by setting variables---normally, each minor
mode has one controlling variable which is non-nil when the mode is enabled
(see Minor Modes). For most minor modes, the controlling variable is per
buffer.

 Emacs contains a number of variables that are always per-buffer. These include
abbrev-mode, auto-fill-function, case-fold-search, comment-column, ctl-arrow,
fill-column, fill-prefix, indent-tabs-mode, left-margin, mode-line-format,
overwrite-mode,
selective-display-ellipses, selective-display, tab-width, and truncate-lines.
Some other variables are always local in every buffer, but they are used for
internal purposes.

 M-x kill-local-variable reads the name of a variable and makes it cease to be
local to the current buffer.  The global value of the variable henceforth is in
effect in this buffer.  Setting the major mode kills all the local variables of
the buffer except for a few specially marked variables that are permanent
locals.

 To set the global value of a variable, regardless of whether the variable has
a local value in the current buffer, you can use the Lisp function
setq-default.  It works like setq. If there is a local value in the current
buffer, the local value is not affected by setq-default; thus, the new global
value may not be visible until you switch to another buffer.  For example,

(setq-default fill-column 75)

setq-default is the only way to set the global value of a variable that has
been marked with make-variable-buffer-local.

 Lisp programs can look at a variable's default value with default-value.  This
function takes a symbol as argument and returns its default value.  The
argument is evaluated; usually you must quote it explicitly.  For example,

(default-value 'fill-column)


ΓòÉΓòÉΓòÉ 33.2.5. Local Variables in Files ΓòÉΓòÉΓòÉ

 A file can specify local variable values for use when you edit the file with
Emacs.  Visiting the file checks for local variables specifications; it
automatically makes these variables local to the buffer, and sets them to the
values specified in the file.

 There are two ways to specify local variable values: in the first line, or
with a local variables list.  Here's how to do this with the first line:

-*- mode: modename; var: value; ... -*-

You can specify any number of variables/value pairs in this way, each pair with
a colon and semicolon as shown above.  The major mode should come first, if it
is mentioned at all.  Here is an example that specifies Lisp mode and sets two
variables with numeric values:

;; -*-Mode: Lisp; fill-column: 75; comment-column: 50; -*-

 A local variables list goes near the end of the file, in the last page.  (It
is often best to put it on a page by itself.)  The local variables list starts
with a line containing the string `Local Variables:', and ends with a line
containing the string `End:'.  In between come the variable names and values,
one set per line, as `variable: value'.  The values are not evaluated; they are
used literally.

Here is an example of a local variables list:

;;; Local Variables: ***
;;; mode:lisp ***
;;; comment-column:0 ***
;;; comment-start: ";;; "  ***
;;; comment-end:"***" ***
;;; End: ***

 As you see, each line starts with the prefix `;;; ' and each line ends with
the suffix `***'.  Emacs recognizes these as the prefix and suffix based on the
first line of the list, by finding them surrounding the magic string `Local
Variables:'; so it automatically discards them from the other lines of the
list.

 The usual reason for using a prefix and/or suffix is to embed the local
variables list in a comment, so it won't confuse other programs that the file
is intended as input for.  The example above is for a language where comment
lines start with `;;; ' and end with `***'; the local values for comment-start
and comment-end customize the rest of Emacs for this unusual syntax. Don't use
a prefix (or a suffix) if you don't need one.

 Two ``variable names'' have special meanings in a local variables list: a
value for the variable mode really sets the major mode, and a value for the
variable eval is simply evaluated as an expression and the value is ignored.
mode and eval are not real variables; setting such variables in any other
context has no such effect.  If mode is used in a local variables list, it
should be the first entry in the list.

 The start of the local variables list must be no more than 3000 characters
from the end of the file, and must be in the last page if the file is divided
into pages.  Otherwise, Emacs will not notice it is there. The purpose of this
is so that a stray `Local Variables:' not in the last page does not confuse
Emacs, and so that visiting a long file that is all one page and has no local
variables list need not take the time to search the whole file.

 You may be tempted to try to turn on Auto Fill mode with a local variable
list.  That is a mistake.  The choice of Auto Fill mode or not is a matter of
individual taste, not a matter of the contents of particular files. If you want
to use Auto Fill, set up major mode hooks with your `.emacs' file to turn it on
(when appropriate) for you alone (see Init File). Don't try to use a local
variable list that would impose your taste on everyone.

 The variable enable-local-variables controls whether to process local
variables lists, and thus gives you a chance to override them. Its default
value is t, which means to process local variables lists.  If you set the value
to nil, Emacs simply ignores local variables lists.  Any other value says to
query you about each local variables list, showing you the local variables list
to consider.

 The eval ``variable'' creates special risks, so there is a separate variable
enable-local-eval to control whether Emacs processes eval variables.  The three
possibilities for the value are t, nil, and anything else, just as for
enable-local-variables.  The default is maybe, which is neither t nor nil, so
normally Emacs queries about eval variable settings.

 Use the command normal-mode to reset the local variables and major mode of a
buffer according to the file name and contents, including the local variables
list if any.  See Choosing Modes.


ΓòÉΓòÉΓòÉ 33.3. Keyboard Macros ΓòÉΓòÉΓòÉ

 A keyboard macro is a command defined by the user to abbreviate a sequence of
keys.  For example, if you discover that you are about to type C-n C-d forty
times, you can speed your work by defining a keyboard macro to do C-n C-d and
calling it with a repeat count of forty.

C-x (
          Start defining a keyboard macro (start-kbd-macro).

C-x )
          End the definition of a keyboard macro (end-kbd-macro).

C-x e
          Execute the most recent keyboard macro (call-last-kbd-macro).

C-u C-x (
          Re-execute last keyboard macro, then add more keys to its definition.

C-x q
          When this point is reached during macro execution, ask for
          confirmation (kbd-macro-query).

M-x name-last-kbd-macro
          Give a command name (for the duration of the session) to the most
          recently defined keyboard macro.

M-x insert-kbd-macro
          Insert in the buffer a keyboard macro's definition, as Lisp code.

 Keyboard macros differ from ordinary Emacs commands in that they are written
in the Emacs command language rather than in Lisp.  This makes it easier for
the novice to write them, and makes them more convenient as temporary hacks.
However, the Emacs command language is not powerful enough as a programming
language to be useful for writing anything intelligent or general.  For such
things, Lisp must be used.

 You define a keyboard macro while executing the commands which are the
definition.  Put differently, as you define a keyboard macro, the definition is
being executed for the first time.  This way, you can see what the effects of
your commands are, so that you don't have to figure them out in your head.
When you are finished, the keyboard macro is defined and also has been, in
effect, executed once.  You can then do the whole thing over again by invoking
the macro.


ΓòÉΓòÉΓòÉ 33.3.1. Basic Use ΓòÉΓòÉΓòÉ

 To start defining a keyboard macro, type the C-x ( command (start-kbd-macro).
From then on, your keys continue to be executed, but also become part of the
definition of the macro.  `Def' appears in the mode line to remind you of what
is going on.  When you are finished, the C-x ) command (end-kbd-macro)
terminates the definition (without becoming part of it!).  For example

C-x ( M-f foo C-x )

defines a macro to move forward a word and then insert `foo'.

 The macro thus defined can be invoked again with the C-x e command
(call-last-kbd-macro), which may be given a repeat count as a numeric argument
to execute the macro many times.  C-x ) can also be given a repeat count as an
argument, in which case it repeats the macro that many times right after
defining it, but defining the macro counts as the first repetition (since it is
executed as you define it).  So, giving C-x ) an argument of 4 executes the
macro immediately 3 additional times.  An argument of zero to C-x e or C-x )
means repeat the macro indefinitely (until it gets an error or you type C-g).

 If you wish to repeat an operation at regularly spaced places in the text,
define a macro and include as part of the macro the commands to move to the
next place you want to use it.  For example, if you want to change each line,
you should position point at the start of a line, and define a macro to change
that line and leave point at the start of the next line. Then repeating the
macro will operate on successive lines.

 After you have terminated the definition of a keyboard macro, you can add to
the end of its definition by typing C-u C-x (.  This is equivalent to plain C-x
( followed by retyping the whole definition so far.  As a consequence it
re-executes the macro as previously defined.

 You can use function keys in a keyboard macro, just like keyboard keys.  You
can even use mouse events, but be careful about that: when the macro replays
the mouse event, it uses the original mouse position of that event, the
position that the mouse had while you were defining the macro.  The effect of
this may be hard to predict.  (Using the current mouse position would be even
less predictable.)

 One thing that doesn't always work well in a keyboard macro is the command
C-M-c (exit-recursive-edit).  When this command exits a recursive edit that
started within the macro, it works as you'd expect.  But if it exits a
recursive edit that started before you invoked the keyboard macro, it also
necessarily exits the keyboard macro as part of the process.


ΓòÉΓòÉΓòÉ 33.3.2. Naming and Saving Keyboard Macros ΓòÉΓòÉΓòÉ

 If you wish to save a keyboard macro for longer than until you define the next
one, you must give it a name using M-x name-last-kbd-macro. This reads a name
as an argument using the minibuffer and defines that name to execute the macro.
The macro name is a Lisp symbol, and defining it in this way makes it a valid
command name for calling with M-x or for binding a key to with global-set-key
(see Keymaps).  If you specify a name that has a prior definition other than
another keyboard macro, an error message is printed and nothing is changed.

 Once a macro has a command name, you can save its definition in a file. Then
it can be used in another editing session.  First, visit the file you want to
save the definition in.  Then use this command:

M-x insert-kbd-macro RET macroname RET

This inserts some Lisp code that, when executed later, will define the same
macro with the same definition it has now.  (You need not understand Lisp code
to do this, because insert-kbd-macro writes the Lisp code for you.)  Then save
the file.  You can load the file later with load-file (see Lisp Libraries).  If
the file you save in is your init file `~/.emacs' (see Init File) then the
macro will be defined each time you run Emacs.

 If you give insert-kbd-macro a prefix argument, it makes additional Lisp code
to record the keys (if any) that you have bound to the keyboard macro, so that
the macro will be reassigned the same keys when you load the file.


ΓòÉΓòÉΓòÉ 33.3.3. Executing Macros with Variations ΓòÉΓòÉΓòÉ

 Using C-x q (kbd-macro-query), you can get an effect similar to that of
query-replace, where the macro asks you each time around whether to make a
change.  When you are defining the macro, type C-x q at the point where you
want the query to occur.  During macro definition, the C-x q does nothing, but
when you run the macro later, C-x q asks you interactively whether to continue.

 The valid responses when C-x q asks are SPC (or y), DEL (or n), ESC (or q),
C-l and C-r.  The answers are the same as in query replace, though not all of
the query-replace options are meaningful.

 Specifically, SPC means to continue.  DEL means to skip the remainder of this
repetition of the macro and start right away with the next repetition.  ESC
means to skip the remainder of this repetition and cancel further repetition.
C-l redraws the screen and asks you again for a character to say what to do.

 C-r enters a recursive editing level, in which you can perform editing which
is not part of the macro.  When you exit the recursive edit using C-M-c, you
are asked again how to continue with the keyboard macro.  If you type a SPC at
this time, the rest of the macro definition is executed.  It is up to you to
leave point and the text in a state such that the rest of the macro will do
what you want.

 C-u C-x q, which is C-x q with a numeric argument, performs a different
function.  It enters a recursive edit reading input from the keyboard, both
when you type it during the definition of the macro, and when it is executed
from the macro.  During definition, the editing you do inside the recursive
edit does not become part of the macro.  During macro execution, the recursive
edit gives you a chance to do some particularized editing.  See Recursive Edit.


ΓòÉΓòÉΓòÉ 33.4. Customizing Key Bindings ΓòÉΓòÉΓòÉ

 This section describes key bindings which map keys to commands, and the
keymaps which record key bindings.  It also explains how to customize key
bindings.

 Recall that a command is a Lisp function whose definition provides for
interactive use.  Like every Lisp function, a command has a function name which
usually consists of lower case letters and hyphens.


ΓòÉΓòÉΓòÉ 33.4.1. Keymaps ΓòÉΓòÉΓòÉ

 The bindings between key sequences and command functions are recorded in data
structures called keymaps.  Emacs has many of these, each used on particular
occasions.

 Recall that a key sequence (key, for short) is a sequence of input events that
have a meaning as a unit.  Input events include characters, function keys and
mouse buttons---all the inputs that you can send to the computer with your
terminal.  A key sequence gets its meaning from its binding, which says what
command it runs.  The function of keymaps is to record these bindings.

 The global keymap is the most important keymap because it is always in effect.
The global keymap defines keys for Fundamental mode; most of these definitions
are common to all (or most) major modes.  Each major or minor mode can have its
own keymap which overrides the definitions of some keys.

 For example, a self-inserting character such as g is self-inserting because
the global keymap binds it to the command self-insert-command.  The standard
Emacs editing characters such as C-a also get their standard meanings from the
global keymap. Commands to rebind keys, such as M-x global-set-key, actually
work by storing the new binding in the proper place in the global map. See
Rebinding.

  Meta characters work differently; Emacs translates each Meta character into a
pair of characters starting with ESC.  When you type the character M-a in a key
sequence, Emacs replaces it with ESC a.  A meta key comes in as a single input
event, but becomes two events for purposes of key bindings.  The reason for
this is historical, and we might change in someday.

 Most modern keyboards have function keys as well as character keys. Function
keys send input events just as character keys do, and keymaps can have bindings
for them.

 On many terminals, typing a function key actually sends the computer a
sequence of characters; the precise details of the sequence depends on which
function key and on the model of terminal you are using.  (Often he sequence
starts with ESC [.)  If Emacs understands your terminal type properly, it
recognizes the character sequences forming function keys wherever they occur in
a key sequence (not just at the beginning).  Thus, for most purposes, you can
pretend the function keys reach Emacs directly and ignore their encoding as
character sequences.

 Mouse buttons also produce input events.  These events come with other
data---the window and position where you pressed or released the button, and a
timestamp.  But only the choice of button matters for key bindings; the other
data matters only if a command looks at it. (Commands designed for mouse
invocation usually do look at the other data.)

 A keymap records definitions for single events.  Interpreting a key sequence
of multiple events involves a chain of keymaps.  The first keymap gives a
definition for the first event; this definition is another keymap, which is
used to look up the second event in the sequence, and so on.

 Key sequences can mix function keys and characters.  For example, C-x SELECT
makes sense.  If you make SELECT a prefix key, then SELECT C-n makes sense.
You can even mix mouse events with keyboard events, but we recommend against
it, because such sequences are inconvenient to type in.


ΓòÉΓòÉΓòÉ 33.4.2. Prefix Keymaps ΓòÉΓòÉΓòÉ

 A prefix key such as C-x or ESC has its own keymap, which holds the definition
for the event that immediately follows that prefix.

 The definition of a prefix key is the keymap to use for looking up the
following event.  The definition can also be a Lisp symbol whose function
definition is the following keymap; the effect is the same, but it provides a
command name for the prefix key that can be used as a description of what the
prefix key is for.  Thus, the binding of C-x is the symbol Ctl-X-Prefix, whose
function definition is the keymap for C-x commands.  The definitions of C-c,
C-x, C-h and ESC as prefix keys appear in the global map, so these prefix keys
are always available.

 Some prefix keymaps are stored in variables with names:

o ctl-x-map is the variable name for the map used for characters that follow
  C-x.

o help-map is for characters that follow C-h.

o esc-map is for characters that follow ESC.  Thus, all Meta characters are
  actually defined by this map.

o ctl-x-4-map is for characters that follow C-x 4.

o mode-specific-map is for characters that follow C-c.


ΓòÉΓòÉΓòÉ 33.4.3. Local Keymaps ΓòÉΓòÉΓòÉ

 So far we have explained the ins and outs of the global map.  Major modes
customize Emacs by providing their own key bindings in local keymaps.  For
example, C mode overrides TAB to make it indent the current line for C code.
Portions of text in the buffer can specify their own keymaps to substitute for
the keymap of the buffer's major mode.

 Minor modes can also have local keymaps.  Whenever a minor mode is in effect,
the definitions in its keymap override both the major mode's local keymap and
the global keymap.

 The local keymaps for Lisp mode, C mode, and several other major modes always
exist even when not in use.  These are kept in variables named lisp-mode-map,
c-mode-map, and so on.  For major modes less often used, the local keymap is
normally constructed only when the mode is used for the first time in a
session.  This is to save space.

 All minor mode keymaps are created in advance.  There is no way to defer their
creation until the minor mode is enabled.

 A local keymap can locally redefine a key as a prefix key by defining it as a
prefix keymap.  If the key is also defined globally as a prefix, then its local
and global definitions (both keymaps) effectively combine: both of them are
used to look up the event that follows the prefix key.  Thus, if the mode's
local keymap defines C-c as another keymap, and that keymap defines C-z as a
command, this provides a local meaning for C-c C-z.  This does not affect other
sequences that start with C-c; If those sequences don't have their own local
bindings, their global bindings remain in effect.

 Another way to think of this is that Emacs handles a multi-event key sequence
by looking in several keymaps, one by one, for a binding of the whole key
sequence.  First it checks the minor mode keymaps for minor modes that are
enabled, then it checks the major mode's keymap, and then it checks the global
keymap.  This is not precisely how key lookup works, but it's good enough for
understanding ordinary circumstances.


ΓòÉΓòÉΓòÉ 33.4.4. Minibuffer Keymaps ΓòÉΓòÉΓòÉ

 The minibuffer has its own set of local keymaps; they contain various
completion and exit commands.

o minibuffer-local-map is used for ordinary input (no completion).

o minibuffer-local-ns-map is similar, except that SPC exits just like RET.
  This is used mainly for Mocklisp compatibility.

o minibuffer-local-completion-map is for permissive completion.

o minibuffer-local-must-match-map is for strict completion and for cautious
  completion.


ΓòÉΓòÉΓòÉ 33.4.5. Changing Key Bindings Interactively ΓòÉΓòÉΓòÉ

 The way to redefine an Emacs key is to change its entry in a keymap. You can
change the global keymap, in which case the change is effective in all major
modes (except those that have their own overriding local definitions for the
same key).  Or you can change the current buffer's local map, which affects all
buffers using the same major mode.

M-x global-set-key RET key cmd RET
          Define key globally to run cmd.

M-x local-set-key RET key cmd RET
          Define key locally (in the major mode now in effect) to run cmd.

M-x global-unset-key RET key
          Make key undefined in the global map.

M-x local-unset-key RET key
          Make key undefined locally (in the major mode now in effect).

 For example, suppose you like to execute commands in a subshell within an
Emacs buffer, instead of suspending Emacs and executing commands in your login
shell.  Normally, C-z is bound to the function suspend-emacs, but you can
change C-z to invoke an interactive subshell within Emacs, by binding it to
shell as follows:

M-x global-set-key RET C-z shell RET

global-set-key reads the command name after the key.  After you press the key,
a message like this appears so that you can confirm that you are binding the
key you want:

Set key C-z to command:

 You can redefine function keys and mouse events in the same way; just type the
function key or click the mouse when it's time to specify the key to rebind.

 You can rebind a key that contains more than one event in the same way.  Emacs
keeps reading the key to rebind until it is a complete key (that is, not a
prefix key).  Thus, if you type C-f for key, that's the end; the minibuffer is
entered immediately to read cmd.  But if you type C-x, another character is
read; if that is 4, another character is read, and so on.  For example,

M-x global-set-key RET C-x 4 $ spell-other-window RET

would redefine C-x 4 $ to run the (fictitious) command spell-other-window.

 You can remove the global definition of a key with global-unset-key.  This
makes the key undefined; if you type it, Emacs will just beep.  Similarly,
local-unset-key makes a key undefined in the current major mode keymap, which
makes the global definition (or lack of one) come back into effect in that
major mode.

 If you have redefined (or undefined) a key and you subsequently wish to
retract the change, undefining the key will not do the job---you need to
redefine the key with its standard definition.  To find the name of the
standard definition of a key, go to a Fundamental mode buffer and use C-h c.
The documentation of keys in this manual also lists their command names.

 If you want to prevent yourself from invoking a command by mistake, it is
better to disable the command than to undefine the key.  A disabled command is
less work to invoke when you really want to. See Disabling.


ΓòÉΓòÉΓòÉ 33.4.6. Rebinding Keys in Your Init File ΓòÉΓòÉΓòÉ

 If you have a set of default definitions that you like to use all the time,
you can put commands in your `.emacs' file by using their Lisp syntax. Thus,
the first global-set-key command in this section could be put in an `.emacs'
file in either of the two following formats:

(global-set-key "\C-z" 'shell)

or as:

(global-set-key [?\C-z] 'shell)

When the key sequence consists of characters, like this one, you can write it
as a string or as a vector.  The first format specifies the key sequence as a
string, "\C-z".  The second format uses a vector to specify the key sequence.
The square brackets (`[...]') delimit the contents of the vector.  The vector
in this example contains just one element, which is the integer code
corresponding to C-z. The question mark is the Lisp syntax for a character
constant; the character must follow with no intervening spaces.

 The single-quote before shell marks it as a constant symbol rather than a
variable.  If you omit the quote, Emacs tries to evaluate shell immediately as
a variable.  This probably causes an error; it certainly isn't what you want.

 Here is another example that binds a key sequence two characters long:

(global-set-key "\C-xl" 'make-symbolic-link)

or:

(global-set-key [?\C-x ?l] 'make-symbolic-link)


ΓòÉΓòÉΓòÉ 33.4.7. Rebinding Function Keys ΓòÉΓòÉΓòÉ

 Key sequences can contain function keys as well as ordinary characters. Just
as Lisp characters (actually integers) represent keyboard characters, Lisp
symbols represent function keys.  If the function key has a word as its label,
then that word is also the name of the corresponding Lisp symbol.  Here are the
Lisp names for other function keys:

left, up, right, down
          Cursor arrow keys.

begin, end, home, next, prior
          Other cursor repositioning keys.

select, print, execute, backtab
insert, undo, redo, clearline
insertline, deleteline, insertchar, deletechar,
          Miscellaneous function keys.

f1 ... f35
          Numbered function keys (across the top of the keyboard).

kp-add, kp-subtract, kp-multiply, kp-divide
kp-backtab, kp-space, kp-tab, kp-enter
kp-separator, kp-decimal, kp-equal
          Keypad keys (to the right of the regular keyboard), with names or
          punctuation.

kp-0, kp-1, ... kp-9
          Keypad keys with digits.

kp-f1, kp-f2, kp-f3, kp-f4
          Keypad PF keys.

A key sequence which contains non-characters must be a vector rather than a
string.  To write a vector, write square brackets containing the vector
elements.  Write spaces to separate the elements.  If an element is a symbol,
simply write the symbol's name---no delimiters or punctuation are needed.  If
an element is a character, write a Lisp character constant, which is `?'
followed by the character as it would appear in a string.

Thus, to bind function key `f1' to the command rmail, write the following:

(global-set-key [f1] 'rmail)

To bind the right-arrow key to the command forward-char, you can use this
expression:

(global-set-key [right] 'forward-char)

using the Lisp syntax for a vector containing the symbol right. (This binding
is present in Emacs by default.)

 You can mix function keys and characters in a key sequence.  This example
binds C-x RIGHT to the command forward-page.

(global-set-key [?\C-x right] 'forward-page)

where ?\C-x is the Lisp character constant for the character C-x.  The vector
element right is a symbol and therefore does not take a question mark.

 You can use the modifier keys CTRL, META, HYPER, SUPER, ALT and SHIFT with
function keys.  To represent these modifiers, prepend the strings `C-', `M-',
`H-', `s-', `A-' and `S-' to the symbol name.  Thus, here is how to make
Hyper-Meta-RIGHT move forward a word:

(global-set-key [H-M-right] 'forward-word)


ΓòÉΓòÉΓòÉ 33.4.8. Rebinding Mouse Buttons ΓòÉΓòÉΓòÉ

 Emacs uses Lisp symbols to designate mouse buttons, too.  The ordinary mouse
events in Emacs are click events; these happen when you press a button and
release it without moving the mouse.  You can also get drag events, when you
move the mouse while holding the button down.  Drag events happen when you
finally let go of the button.

 The symbols for basic click events are mouse-1 for the leftmost button,
mouse-2 for the next, and so on.  Here is how you can redefine the second mouse
button to split the current window:

(global-set-key [mouse-2] 'split-window-vertically)

 The symbols for drag events are similar, but have the prefix `drag-' before
the word `mouse'.  For example, dragging the left button generates a
drag-mouse-1 event.

 You can also request events when the mouse button is pressed down. These
events start with `down-' instead of `drag-'.  Such events are generated only
if they have key bindings.  When you get a button-down event, a corresponding
click or drag event will always follow.

 The symbols for mouse events also indicate the status of the modifier keys,
with the usual prefixes `C-', `M-', `H-', `s-', `A-' and `S-'.  These always
follow `drag-' or `down-'.

 A frame includes areas that don't show text from the buffer, such as the mode
line and the scroll bar.  You can tell whether a mouse button comes from a
special area of the screen by means of dummy ``prefix keys.''  For example, if
you click the mouse in the mode line, you get the prefix key mode-line before
the ordinary mouse-button symbol.  Thus, here is how to define the command for
clicking the left button in a mode line to run scroll-up:

(global-set-key [mode-line mouse-1] 'scroll-up)

 Here is the complete list of these dummy prefix keys and their meanings:

mode-line
          The mouse was in the mode line of a window.

vertical-line
          The mouse was in the vertical line separating side-by-side windows.

vertical-scroll-bar
          The mouse was in a horizontal scroll bar.  This is the kind of scroll
          bar people normally use.

horizontal-scroll-bar
          The mouse was in a horizontal scroll bar.  Horizontal scroll bars do
          horizontal scrolling, and people don't use them often.

 You can put more than one mouse button in a key sequence, but it isn't usual
to do so.


ΓòÉΓòÉΓòÉ 33.4.9. Disabling Commands ΓòÉΓòÉΓòÉ

 Disabling a command marks the command as requiring confirmation before it can
be executed.  The purpose of disabling a command is to prevent beginning users
from executing it by accident and being confused.

 Attempting to invoke a disabled command interactively in Emacs causes the
display of a window containing the command's name, its documentation, and some
instructions on what to do immediately; then Emacs asks for input saying
whether to execute the command as requested, enable it and execute, or cancel
it.  If you decide to enable the command, you are asked whether to do this
permanently or just for the current session.  Enabling permanently works by
automatically editing your `.emacs' file.

 The direct mechanism for disabling a command is to have a non-nil disabled
property on the Lisp symbol for the command.  Here is the Lisp program to do
this:

(put 'delete-region 'disabled t)

 If the value of the disabled property is a string, that string is included in
the message printed when the command is used:

(put 'delete-region 'disabled
     "Text deleted this way cannot be yanked back!\n")

 You can make a command disabled either by editing the `.emacs' file directly
or with the command M-x disable-command, which edits the `.emacs' file for you.
Likewise, M-x enable-command edits `.emacs' to enable a command permanently.
See Init File.

 Whether a command is disabled is independent of what key is used to invoke it;
it also applies if the command is invoked using M-x. Disabling a command has no
effect on calling it as a function from Lisp programs.


ΓòÉΓòÉΓòÉ 33.5. Keyboard Translations ΓòÉΓòÉΓòÉ

 Some keyboards do not make it convenient to send all the special characters
that Emacs uses.  The most common problem case is the DEL character.  Some
keyboards provide no convenient way to type this very important
character---usually because they were designed to expect the character C-h to
be used for deletion.  On these keyboard, if you press the key normally used
for deletion, Emacs handles the C-h as a prefix character and offers you a list
of help options, which is not what you want.

 You can work around this problem within Emacs by setting up keyboard
translations to turn C-h into DEL and DEL into C-h, as follows:

;; Translate C-h to DEL.
(keyboard-translate ?\C-h ?\C-?)
;; Translate DEL to C-h.
(keyboard-translate ?\C-? ?\C-h)

 Keyboard translations are not the same as key bindings in keymaps (see
Keymaps).  Emacs contains numerous keymaps that apply in different situations,
but there is only one set of keyboard translations, and it applies to every
character that Emacs reads from the terminal.  Keyboard translations take place
at the lowest level of input processing; the keys that are looked up in keymaps
contain the characters that result from keyboard translation.

 For full information about how to use keyboard translations, see Translating
Input.


ΓòÉΓòÉΓòÉ 33.6. The Syntax Table ΓòÉΓòÉΓòÉ

 All the Emacs commands which parse words or balance parentheses are controlled
by the syntax table.  The syntax table says which characters are opening
delimiters, which are parts of words, which are string quotes, and so on.  Each
major mode has its own syntax table (though sometimes related major modes use
the same one) which it installs in each buffer that uses that major mode.  The
syntax table installed in the current buffer is the one that all commands use,
so we call it ``the'' syntax table.  A syntax table is a Lisp object, a vector
of length 256 whose elements are numbers.

 To display a description of the contents of the current syntax table, type C-h
s (describe-syntax).  The description of each character includes both the
string you would have to give to modify-syntax-entry to set up that character's
current syntax, and some English to explain that string if necessary.

 For full information on the syntax table, see Syntax Table.


ΓòÉΓòÉΓòÉ 33.7. The Init File, ~/.emacs ΓòÉΓòÉΓòÉ

 When Emacs is started, it normally loads a Lisp program from the file `.emacs'
in your home directory.  We call this file your init file because it specifies
how to initialize Emacs for you.  You can use the command line switches `-q'
and `-u' to tell Emacs whether to load an init file, and which one (see
Entering Emacs).

 There can also be a default init file, which is the library named
`default.el', found via the standard search path for libraries.  The Emacs
distribution contains no such library; your site may create one for local
customizations.  If this library exists, it is loaded whenever you start Emacs
(except when you specify `-q'). But your init file, if any, is loaded first; if
it sets inhibit-default-init non-nil, then `default' is not loaded.

 If you have a large amount of code in your `.emacs' file, you should move it
into another file such as `~/something.el', byte-compile it, and make your
`.emacs' file load it with (load "~/something"). See Byte Compilation, for more
information about compiling Emacs Lisp programs.


ΓòÉΓòÉΓòÉ 33.7.1. Init File Syntax ΓòÉΓòÉΓòÉ

 The `.emacs' file contains one or more Lisp function call expressions.  Each
of these consists of a function name followed by arguments, all surrounded by
parentheses.  For example, (setq fill-column 60) calls the function setq to set
the variable fill-column (see Filling) to 60.

 The second argument to setq is an expression for the new value of the
variable.  This can be a constant, a variable, or a function call expression.
In `.emacs', constants are used most of the time.  They can be:

Numbers:
          Numbers are written in decimal, with an optional initial minus sign.

Strings:
          Lisp string syntax is the same as C string syntax with a few extra
          features.  Use a double-quote character to begin and end a string
          constant.

          In a string, you can include newlines and special characters
          literally. But often it is cleaner to use backslash sequences for
          them: `\n' for newline, `\b' for backspace, `\r' for carriage return,
          `\t' for tab, `\f' for formfeed (control-L), `\e' for escape, `\\'
          for a backslash, `\"' for a double-quote, or `\ooo' for the character
          whose octal code is ooo. Backslash and double-quote are the only
          characters for which backslash sequences are mandatory.

          `\C-' can be used as a prefix for a control character, as in `\C-s'
          for ASCII control-S, and `\M-' can be used as a prefix for a Meta
          character, as in `\M-a' for Meta-A or `\M-\C-a' for Control-Meta-A.

Characters:
          Lisp character constant syntax consists of a `?' followed by either a
          character or an escape sequence starting with `\'. Examples: ?x, ?\n,
          ?\", ?\).  Note that strings and characters are not interchangeable
          in Lisp; some contexts require one and some contexts require the
          other.

True:
          t stands for `true'.

False:
          nil stands for `false'.

Other Lisp objects:
          Write a single-quote (') followed by the Lisp object you want.


ΓòÉΓòÉΓòÉ 33.7.2. Init File Examples ΓòÉΓòÉΓòÉ

 Here are some examples of doing certain commonly desired things with Lisp
expressions:

o Make TAB in C mode just insert a tab if point is in the middle of a line.

    (setq c-tab-always-indent nil)

  Here we have a variable whose value is normally t for `true' and the
  alternative is nil for `false'.

o Make searches case sensitive by default (in all buffers that do not override
  this).

    (setq-default case-fold-search nil)

  This sets the default value, which is effective in all buffers that do not
  have local values for the variable.  Setting case-fold-search with setq
  affects only the current buffer's local value, which is not what you probably
  want to do in an init file.

o Make Text mode the default mode for new buffers.

    (setq default-major-mode 'text-mode)

  Note that text-mode is used because it is the command for entering Text mode.
  The single-quote before it makes the symbol a constant; otherwise, text-mode
  would be treated as a variable name.

o Turn on Auto Fill mode automatically in Text mode and related modes.

    (add-hook 'text-mode-hook
      '(lambda () (auto-fill-mode 1)))

  This shows how to add a hook function to a normal hook variable (see Hooks).
  The function we supply is a list starting with lambda, with a single-quote in
  front of it to make it a list constant rather than an expression.

  It's beyond the scope of this manual to explain Lisp functions, but for this
  example it is enough to know that the effect is to execute (auto-fill-mode 1)
  when Text mode is entered.  You can replace it with any other expression that
  you like, or with several expressions in a row.

  Emacs comes with a function named turn-on-auto-fill whose definition is
  (lambda () (auto-fill-mode 1)).  Thus, a simpler way to write the above
  example is as follows:

    (add-hook 'text-mode-hook 'turn-on-auto-fill)

o Load the installed Lisp library named `foo' (actually a file `foo.elc' or
  `foo.el' in a standard Emacs directory).

    (load "foo")

  When the argument to load is a relative file name, not starting with `/' or
  `~', load searches the directories in load-path (see Lisp Libraries).

o Load the compiled Lisp file `foo.elc' from your home directory.

    (load "~/foo.elc")

  Here an absolute file name is used, so no searching is done.

o Rebind the key C-x l to run the function make-symbolic-link.

    (global-set-key "\C-xl" 'make-symbolic-link)

  or

    (define-key global-map "\C-xl" 'make-symbolic-link)

  Note once again the single-quote used to refer to the symbol
  make-symbolic-link instead of its value as a variable.

o Do the same thing for C mode only.

    (define-key c-mode-map "\C-xl" 'make-symbolic-link)

o Redefine all keys which now run next-line in Fundamental mode so that they
  run forward-line instead.

    (substitute-key-definition 'next-line 'forward-line
                               global-map)

o Make C-x C-v undefined.

    (global-unset-key "\C-x\C-v")

  One reason to undefine a key is so that you can make it a prefix. Simply
  defining C-x C-v anything will make C-x C-v a prefix, but C-x C-v must first
  be freed of its usual non-prefix definition.

o Make `$' have the syntax of punctuation in Text mode. Note the use of a
  character constant for `$'.

    (modify-syntax-entry ?\$ "." text-mode-syntax-table)

o Enable the use of the command eval-expression without confirmation.

    (put 'eval-expression 'disabled nil)


ΓòÉΓòÉΓòÉ 33.7.3. Terminal-specific Initialization ΓòÉΓòÉΓòÉ

 Each terminal type can have a Lisp library to be loaded into Emacs when it is
run on that type of terminal.  For a terminal type named termtype, the library
is called `term/termtype' and it is found by searching the directories
load-path as usual and trying the suffixes `.elc' and `.el'.  Normally it
appears in the subdirectory `term' of the directory where most Emacs libraries
are kept.

 The usual purpose of the terminal-specific library is to define the escape
sequences used by the terminal's function keys using the library `keypad.el'.
See the file `term/vt100.el' for an example of how this is done.

 When the terminal type contains a hyphen, only the part of the name before the
first hyphen is significant in choosing the library name. Thus, terminal types
`aaa-48' and `aaa-30-rv' both use the library `term/aaa'.  The code in the
library can use (getenv "TERM") to find the full terminal type name.

 The library's name is constructed by concatenating the value of the variable
term-file-prefix and the terminal type.  Your `.emacs' file can prevent the
loading of the terminal-specific library by setting term-file-prefix to nil.

 Emacs runs the hook term-setup-hook at the end of initialization, after both
your `.emacs' file and any terminal-specific library have been read in.  Add
hook functions to this hook if you wish to override part of any of the
terminal-specific libraries and to define initializations for terminals that do
not have a library.  See Hooks.


ΓòÉΓòÉΓòÉ 33.7.4. How Emacs Finds Your Init File ΓòÉΓòÉΓòÉ

 Normally Emacs uses the environment variable HOME to find `.emacs'; that's
what `~' means in a file name.  But if you have done su, Emacs tries to find
your own `.emacs', not that of the user you are currently pretending to be.
The idea is that you should get your own editor customizations even if you are
running as the super user.

 More precisely, Emacs first determines which user's init file to use. It gets
the user name from the environment variables USER and LOGNAME; if neither of
those exists, it uses effective user-ID. If that user name matches the real
user-ID, then Emacs uses HOME; otherwise, it looks up the home directory
corresponding to that user name in the system's data base of users.


ΓòÉΓòÉΓòÉ 33.8. Quitting and Aborting ΓòÉΓòÉΓòÉ

C-g
          Quit.  Cancel running or partially typed command.

C-]
          Abort innermost recursive editing level and cancel the command which
          invoked it (abort-recursive-edit).

M-x top-level
          Abort all recursive editing levels that are currently executing.

C-x u
          Cancel an already-executed command, usually (undo).

 There are two ways of cancelling commands which are not finished executing:
quitting with C-g, and aborting with C-] or M-x top-level.  Quitting cancels a
partially typed command or one which is already running.  Aborting exits a
recursive editing level and cancels the command that invoked the recursive
edit. (See Recursive Edit.)

 Quitting with C-g is used for getting rid of a partially typed command, or a
numeric argument that you don't want.  It also stops a running command in the
middle in a relatively safe way, so you can use it if you accidentally give a
command which takes a long time.  In particular, it is safe to quit out of
killing; either your text will all still be in the buffer, or it will all be in
the kill ring (or maybe both).  Quitting an incremental search does special
things documented under searching; in general, it may take two successive C-g
characters to get out of a search.

 C-g works by setting the variable quit-flag to t the instant C-g is typed;
Emacs Lisp checks this variable frequently and quits if it is non-nil.  C-g is
only actually executed as a command if you type it while Emacs is waiting for
input.

 If you quit with C-g a second time before the first C-g is recognized, you
activate the ``emergency escape'' feature and return to the shell.  See
Emergency Escape.

 There may be times when you cannot quit.  When Emacs is waiting for the
operating system to do something, quitting is impossible unless special pains
are taken for the particular system call within Emacs where the waiting occurs.
We have done this for the system calls that users are likely to want to quit
from, but it's possible you will find another.  In one very common
case---waiting for file input or output using NFS---Emacs itself knows how to
quit, but most NFS implementations simply do not allow user programs to stop
waiting for NFS when the NFS server is hung.

 Aborting with C-] (abort-recursive-edit) is used to get out of a recursive
editing level and cancel the command which invoked it.  Quitting with C-g does
not do this, and could not do this, because it is used to cancel a partially
typed command within the recursive editing level.  Both operations are useful.
For example, if you are in a recursive edit and type C-u 8 to enter a numeric
argument, you can cancel that argument with C-g and remain in the recursive
edit.

 The command M-x top-level is equivalent to ``enough'' C-] commands to get you
out of all the levels of recursive edits that you are in.  C-] gets you out one
level at a time, but M-x top-level goes out all levels at once.  Both C-] and
M-x top-level are like all other commands, and unlike C-g, in that they are
effective only when Emacs is ready for a command.  C-] is an ordinary key and
has its meaning only because of its binding in the keymap. See Recursive Edit.

 C-x u (undo) is not strictly speaking a way of cancelling a command, but you
can think of it as cancelling a command already finished executing.  See Undo.


ΓòÉΓòÉΓòÉ 33.9. Dealing with Emacs Trouble ΓòÉΓòÉΓòÉ

 This section describes various conditions in which Emacs fails to work
normally, and how to recognize them and correct them.


ΓòÉΓòÉΓòÉ 33.9.1. If DEL Fails to Delete ΓòÉΓòÉΓòÉ

 If you find that DEL enters Help like Control-h instead of deleting a
character, your terminal is sending the wrong code for DEL.  You can work
around this problem by changing the keyboard translation table (see Keyboard
Translations).


ΓòÉΓòÉΓòÉ 33.9.2. Recursive Editing Levels ΓòÉΓòÉΓòÉ

 Recursive editing levels are important and useful features of Emacs, but they
can seem like malfunctions to the user who does not understand them.

 If the mode line has square brackets `[...]' around the parentheses that
contain the names of the major and minor modes, you have entered a recursive
editing level.  If you did not do this on purpose, or if you don't understand
what that means, you should just get out of the recursive editing level.  To do
so, type M-x top-level.  This is called getting back to top level.  See
Recursive Edit.


ΓòÉΓòÉΓòÉ 33.9.3. Garbage on the Screen ΓòÉΓòÉΓòÉ

 If the data on the screen looks wrong, the first thing to do is see whether
the text is really wrong.  Type C-l, to redisplay the entire screen.  If the
screen appears correct after this, the problem was entirely in the previous
screen update.

 Display updating problems often result from an incorrect termcap entry for the
terminal you are using.  The file `etc/TERMS' in the Emacs distribution gives
the fixes for known problems of this sort. `INSTALL' contains general advice
for these problems in one of its sections.  Very likely there is simply
insufficient padding for certain display operations.  To investigate the
possibility that you have this sort of problem, try Emacs on another terminal
made by a different manufacturer. If problems happen frequently on one kind of
terminal but not another kind, it is likely to be a bad termcap entry, though
it could also be due to a bug in Emacs that appears for terminals that have or
that lack specific features.


ΓòÉΓòÉΓòÉ 33.9.4. Garbage in the Text ΓòÉΓòÉΓòÉ

 If C-l shows that the text is wrong, try undoing the changes to it using C-x u
until it gets back to a state you consider correct.  Also try C-h l to find out
what command you typed to produce the observed results.

 If a large portion of text appears to be missing at the beginning or end of
the buffer, check for the word `Narrow' in the mode line. If it appears, the
text is still present, but temporarily off-limits. To make it accessible again,
type C-x n w.  See Narrowing.


ΓòÉΓòÉΓòÉ 33.9.5. Spontaneous Entry to Incremental Search ΓòÉΓòÉΓòÉ

 If Emacs spontaneously displays `I-search:' at the bottom of the screen, it
means that the terminal is sending C-s and C-q according to the poorly designed
xon/xoff ``flow control'' protocol.

 If this happens to you, your best recourse is to put the terminal in a mode
where it will not use flow control, or give it so much padding that it will
never send a C-s.  (One way to increase the amount of padding is to set the
variable baud-rate to a larger value.  Its value is the terminal output speed,
measured in the conventional units of baud.)

 If you don't succeed in turning off flow control, the next best thing is to
tell Emacs to cope with it.  To do this, call the function enable-flow-control.

 Typically there are particular terminal types with which you must use flow
control.  You can conveniently ask for flow control on those terminal types
only, using enable-flow-control-on.  For example, if you find you must use flow
control on VT-100 and H19 terminals, put the following in your `.emacs' file:

(enable-flow-control-on "vt100" "h19")

 When flow control is enabled, you must type C-\ to get the effect of a C-s,
and type C-^ to get the effect of a C-q.  (These aliases work by means of
keyboard translations; see Keyboard Translations.)


ΓòÉΓòÉΓòÉ 33.9.6. Emergency Escape ΓòÉΓòÉΓòÉ

 Because at times there have been bugs causing Emacs to loop without checking
quit-flag, a special feature causes Emacs to be suspended immediately if you
type a second C-g while the flag is already set, so you can always get out of
GNU Emacs.  Normally Emacs recognizes and clears quit-flag (and quits!) quickly
enough to prevent this from happening.

 When you resume Emacs after a suspension caused by multiple C-g, it asks two
questions before going back to what it had been doing:

Auto-save? (y or n)
Abort (and dump core)? (y or n)

Answer each one with y or n followed by RET.

 Saying y to `Auto-save?' causes immediate auto-saving of all modified buffers
in which auto-saving is enabled.

 Saying y to `Abort (and dump core)?' causes an illegal instruction to be
executed, dumping core.  This is to enable a wizard to figure out why Emacs was
failing to quit in the first place.  Execution does not continue after a core
dump.  If you answer n, execution does continue.  With luck, GNU Emacs will
ultimately check quit-flag and quit normally. If not, and you type another C-g,
it is suspended again.

 If Emacs is not really hung, just slow, you may invoke the double C-g feature
without really meaning to.  Then just resume and answer n to both questions,
and you will arrive at your former state. Presumably the quit you requested
will happen soon.

 The double-C-g feature is turned off when Emacs is running under the X Window
System, since the you can use the window manager to kill Emacs or to create
another window and run another program.


ΓòÉΓòÉΓòÉ 33.9.7. Help for Total Frustration ΓòÉΓòÉΓòÉ

 If using Emacs (or something else) becomes terribly frustrating and none of
the techniques described above solve the problem, Emacs can still help you.

 First, if the Emacs you are using is not responding to commands, type C-g C-g
to get out of it and then start a new one.

 Second, type M-x doctor RET.

 The doctor will help you feel better.  Each time you say something to the
doctor, you must end it by typing RET RET.  This lets the doctor know you are
finished.


ΓòÉΓòÉΓòÉ 33.10. Reporting Bugs ΓòÉΓòÉΓòÉ

 Sometimes you will encounter a bug in Emacs.  Although we cannot promise we
can or will fix the bug, and we might not even agree that it is a bug, we want
to hear about bugs you encounter in case we do want to fix them.

 To make it possible for us to fix a bug, you must report it.  In order to do
so effectively, you must know when and how to do it.


ΓòÉΓòÉΓòÉ 33.10.1. When Is There a Bug ΓòÉΓòÉΓòÉ

 If Emacs executes an illegal instruction, or dies with an operating system
error message that indicates a problem in the program (as opposed to something
like ``disk full''), then it is certainly a bug.

 If Emacs updates the display in a way that does not correspond to what is in
the buffer, then it is certainly a bug.  If a command seems to do the wrong
thing but the problem corrects itself if you type C-l, it is a case of
incorrect display updating.

 Taking forever to complete a command can be a bug, but you must make certain
that it was really Emacs's fault.  Some commands simply take a long time.  Type
C-g and then C-h l to see whether the input Emacs received was what you
intended to type; if the input was such that you know it should have been
processed quickly, report a bug.  If you don't know whether the command should
take a long time, find out by looking in the manual or by asking for
assistance.

 If a command you are familiar with causes an Emacs error message in a case
where its usual definition ought to be reasonable, it is probably a bug.

 If a command does the wrong thing, that is a bug.  But be sure you know for
certain what it ought to have done.  If you aren't familiar with the command,
or don't know for certain how the command is supposed to work, then it might
actually be working right.  Rather than jumping to conclusions, show the
problem to someone who knows for certain.

 Finally, a command's intended definition may not be best for editing with.
This is a very important sort of problem, but it is also a matter of judgment.
Also, it is easy to come to such a conclusion out of ignorance of some of the
existing features.  It is probably best not to complain about such a problem
until you have checked the documentation in the usual ways, feel confident that
you understand it, and know for certain that what you want is not available.
If you are not sure what the command is supposed to do after a careful reading
of the manual, check the index and glossary for any terms that may be unclear.

 If you still do not understand, that indicates a bug in the manual, which you
should report.  The manual's job is to make everything clear to people who are
not Emacs experts---including you.  It is just as important to report
documentation bugs as program bugs.

 If the on-line documentation string of a function or variable disagrees with
the manual, one of them must be wrong; that is a bug.


ΓòÉΓòÉΓòÉ 33.10.2. Understanding Bug Reporting ΓòÉΓòÉΓòÉ

 When you decide that there is a bug, it is important to report it and to
report it in a way which is useful.  What is most useful is an exact
description of what commands you type, starting with the shell command to run
Emacs, until the problem happens.

 The most important principle in reporting a bug is to report facts, not
hypotheses or categorizations.  It is always easier to report the facts, but
people seem to prefer to strain to posit explanations and report them instead.
If the explanations are based on guesses about how Emacs is implemented, they
will be useless; we will have to try to figure out what the facts must have
been to lead to such speculations.  Sometimes this is impossible.  But in any
case, it is unnecessary work for us.

 For example, suppose that you type C-x C-f /glorp/baz.ugh RET, visiting a file
which (you know) happens to be rather large, and Emacs prints out `I feel
pretty today'.  The best way to report the bug is with a sentence like the
preceding one, because it gives all the facts and nothing but the facts.

 Do not assume that the problem is due to the size of the file and say, ``When
I visit a large file, Emacs prints out `I feel pretty today'.'' This is what we
mean by ``guessing explanations''.  The problem is just as likely to be due to
the fact that there is a `z' in the file name.  If this is so, then when we got
your report, we would try out the problem with some ``large file'', probably
with no `z' in its name, and not find anything wrong.  There is no way in the
world that we could guess that we should try visiting a file with a `z' in its
name.

 Alternatively, the problem might be due to the fact that the file starts with
exactly 25 spaces.  For this reason, you should make sure that you inform us of
the exact contents of any file that is needed to reproduce the bug.  What if
the problem only occurs when you have typed the C-x C-a command previously?
This is why we ask you to give the exact sequence of characters you typed since
starting to use Emacs.

 You should not even say ``visit a file'' instead of C-x C-f unless you know
that it makes no difference which visiting command is used. Similarly, rather
than saying ``if I have three characters on the line,'' say ``after I type RET
A B C RET C-p,'' if that is the way you entered the text.


ΓòÉΓòÉΓòÉ 33.10.3. Checklist for Bug Reports ΓòÉΓòÉΓòÉ

 The best way to send a bug report is to mail it electronically to the Emacs
maintainers at `[e-mail]'.

 If you'd like to read the bug reports, you can find them on the repeater
newsgroup `gnu.emacs.bugs'; keep in mind, however, that as a spectator you
should not criticize anything about what you see there. The purpose of bug
reports is to give information to the Emacs maintainers.  Spectators are
welcome only as long as they do not interfere with this.

 Please do not post bug reports using netnews; mail is more reliable than
netnews about reporting your correct address, which we may need in order to ask
you for more information.

 If you can't send electronic mail, then mail the bug report on paper to this
address:

GNU Emacs Bugs Free Software Foundation 675 Mass Ave Cambridge, MA 02139

 We do not promise to fix the bug; but if the bug is serious, or ugly, or easy
to fix, chances are we will want to.

 To enable maintainers to investigate a bug, your report should include all
these things:

o The version number of Emacs.  Without this, we won't know whether there is
  any point in looking for the bug in the current version of GNU Emacs.

  You can get the version number by typing M-x emacs-version RET.  If that
  command does not work, you probably have something other than GNU Emacs, so
  you will have to report the bug somewhere else.

o The type of machine you are using, and the operating system name and version
  number.

o The operands you gave to the configure command when you installed Emacs.

o A complete list of any modifications you have made to the Emacs source. (We
  may not have time to investigate the bug unless it happens in an unmodified
  Emacs.  But if you've made modifications and don't tell us, then you are
  sending us on a wild goose chase.)

  Be precise about these changes.  A description in English is not
  enough---send a context diff for them.

  Adding files of your own (such as a machine description for a machine we
  don't support) is a modification of the source.

o Details of any other deviations from the standard procedure for installing
  GNU Emacs.

o The complete text of any files needed to reproduce the bug.

   If you can tell us a way to cause the problem without visiting any files,
  please do so.  This makes it much easier to debug.  If you do need files,
  make sure you arrange for us to see their exact contents.  For example, it
  can often matter whether there are spaces at the ends of lines, or a newline
  after the last line in the buffer (nothing ought to care whether the last
  line is terminated, but try telling the bugs that).

o The precise commands we need to type to reproduce the bug.

   The easy way to record the input to Emacs precisely is to to write a dribble
  file.  To start the file, execute the Lisp expression

    (open-dribble-file "~/dribble")

  using M-ESC or from the `*scratch*' buffer just after starting Emacs.  From
  then on, Emacs copies all your input to the specified dribble file until the
  Emacs process is killed.

o For possible display bugs, the terminal type (the value of environment
  variable TERM), the complete termcap entry for the terminal from
  `/etc/termcap' (since that file is not identical on all machines), and the
  output that Emacs actually sent to the terminal.

  The way to collect the terminal output is to execute the Lisp expression

    (open-termscript "~/termscript")

  using M-ESC or from the `*scratch*' buffer just after starting Emacs.  From
  then on, Emacs copies all terminal output to the specified termscript file as
  well, until the Emacs process is killed. If the problem happens when Emacs
  starts up, put this expression into your `.emacs' file so that the termscript
  file will be open when Emacs displays the screen for the first time.

  Be warned: it is often difficult, and sometimes impossible, to fix a
  terminal-dependent bug without access to a terminal of the type that
  stimulates the bug.

o A description of what behavior you observe that you believe is incorrect.
  For example, ``The Emacs process gets a fatal signal,'' or, ``The resulting
  text is as follows, which I think is wrong.''

  Of course, if the bug is that Emacs gets a fatal signal, then one can't miss
  it.  But if the bug is incorrect text, the maintainer might fail to notice
  what is wrong.  Why leave it to chance?

  Even if the problem you experience is a fatal signal, you should still say so
  explicitly.  Suppose something strange is going on, such as, your copy of the
  source is out of sync, or you have encountered a bug in the C library on your
  system.  (This has happened!)  Your copy might crash and the copy here would
  not.  If you said to expect a crash, then when Emacs here fails to crash, we
  would know that the bug was not happening.  If you don't say to expect a
  crash, then we would not know whether the bug was happening.  We would not be
  able to draw any conclusion from our observations.

  If the manifestation of the bug is an Emacs error message, it is important to
  report not just the text of the error message but a backtrace showing how the
  Lisp program in Emacs arrived at the error. To make the backtrace, execute
  the Lisp expression (setq debug-on-error t) before the error happens (that is
  to say, you must execute that expression and then make the bug happen).  This
  causes the Lisp debugger to run, showing you a backtrace.  Copy the text of
  the debugger's backtrace into the bug report.

  This use of the debugger is possible only if you know how to make the bug
  happen again.  Do note the error message the first time the bug happens, so
  if you can't make it happen again, you can report at least the error message.

o Check whether any programs you have loaded into the Lisp world, including
  your `.emacs' file, set any variables that may affect the functioning of
  Emacs.  Also, see whether the problem happens in a freshly started Emacs
  without loading your `.emacs' file (start Emacs with the -q switch to prevent
  loading the init file.)  If the problem does not occur then, you must report
  the precise contents of any programs that you must load into the Lisp world
  in order to cause the problem to occur.

o If the problem does depend on an init file or other Lisp programs that are
  not part of the standard Emacs system, then you should make sure it is not a
  bug in those programs by complaining to their maintainers first.  After they
  verify that they are using Emacs in a way that is supposed to work, they
  should report the bug.

o If you wish to mention something in the GNU Emacs source, show the portion in
  its context.  Don't just give a line number.

  The line numbers in the development sources don't match those in your
  sources.  It would take extra work for the maintainers to determine what code
  is in your version at a given line number, and we could not be certain.

o Additional information from a debugger might enable someone to find a problem
  on a machine which he does not have available.  However, you need to think
  when you collect this information if you want it to be useful.

  For example, many people send just a backtrace, but that is never useful by
  itself.  A simple backtrace with arguments conveys little about what is
  happening inside GNU Emacs, because most of the arguments listed in the
  backtrace are pointers to Lisp objects.  The numeric values of these pointers
  have no significance whatever; all that matters is the contents of the
  objects they point to (and most of the contents are themselves pointers).

  To provide useful information, you need to show the values of Lisp objects in
  Lisp notation.  Do this for each variable which is a Lisp object, in several
  stack frames near the bottom of the stack.  Look at the source to see which
  variables are Lisp objects, because the debugger thinks of them as integers.

  To show a variable's value in Lisp syntax, first print its value, then use
  the GDB command pr to print the Lisp object in Lisp syntax. (If you must use
  another debugger, call the function debug_print with the object as an
  argument.)

Here are some things that are not necessary:

o A description of the envelope of the bug---this is not necessary for a
  reproducible bug.

  Often people who encounter a bug spend a lot of time investigating which
  changes to the input file will make the bug go away and which changes will
  not affect it.

  This is often time consuming and not very useful, because the way we will
  find the bug is by running a single example under the debugger with
  breakpoints, not by pure deduction from a series of examples.  You might as
  well save time by not doing this.

  Of course, if you can find a simpler example to report instead of the
  original one, that is a convenience.  Errors in the output will be easier to
  spot, running under the debugger will take less time, etc.

  However, simplification is not vital; if you don't want to do this, please
  report the bug with your original test case.

o A patch for the bug.

  A patch for the bug is useful if it is a good one.  But don't omit the
  necessary information, such as the test case, on the assumption that a patch
  is all we need.  We might see problems with your patch and decide to fix the
  problem another way, or we might not understand it at all.

  And if we can't understand what bug you are trying to fix, or why your patch
  should be an improvement, we mustn't install it.  A test case will help us to
  understand.

  See Sending Patches, for guidelines on how to make it easy for us to
  understand and install your patches.

o A guess about what the bug is or what it depends on.

  Such guesses are usually wrong.  Even experts can't guess right about such
  things without first using the debugger to find the facts.


ΓòÉΓòÉΓòÉ 33.10.4. Sending Patches for GNU Emacs ΓòÉΓòÉΓòÉ

 If you would like to write bug fixes or improvements for GNU Emacs, that is
very helpful.  When you send your changes, please follow these guidelines to
make it easy for the maintainers to use them.

 If you don't follow these guidelines, your information might still be useful,
but using it will take extra work.  Maintaining GNU Emacs is a lot of work in
the best of circumstances, and we can't keep up unless you do your best to
help.

o Send an explanation with your changes of what problem they fix or what
  improvement they bring about.  For a bug fix, just include a copy of the bug
  report, and explain why the change fixes the bug.

  (Referring to a bug report is not as good as including it, because then we
  will have to look it up, and we have probably already deleted it if we've
  already fixed the bug.)

o Always include a proper bug report for the problem you think you have fixed.
  We need to convince ourselves that the change is right before installing it.
  Even if it is correct, we might have trouble understanding it if we don't
  have a way to reproduce the problem.

o Include all the comments that are appropriate to help people reading the
  source in the future understand why this change was needed.

o Don't mix together changes made for different reasons. Send them
  individually.

  If you make two changes for separate reasons, then we might not want to
  install them both.  We might want to install just one.  If you send them all
  jumbled together in a single set of diffs, we have to do extra work to
  disentangle them---to figure out which parts of the change serve which
  purpose.  If we don't have time for this, we might have to ignore your
  changes entirely.

  If you send each change as soon as you have written it, with its own
  explanation, then the two changes never get tangled up, and we can consider
  each one properly without any extra work to disentangle them.

o Send each change as soon as that change is finished.  Sometimes people think
  they are helping us by accumulating many changes to send them all together.
  As explained above, this is absolutely the worst thing you could do.

  Since you should send each change separately, you might as well send it right
  away.  That gives us the option of installing it immediately if it is
  important.

o Use `diff -c' to make your diffs.  Diffs without context are hard to install
  reliably.  More than that, they are hard to study; we must always study a
  patch to decide whether we want to install it.  Unidiff format is better than
  contextless diffs, but not as easy to read as `-c' format.

  If you have GNU diff, use `diff -cp', which shows the name of the function
  that each change occurs in.

o Write the change log entries for your changes.  This is both to save us the
  extra work of writing them, and to help explain your changes so we can
  understand them.

  The purpose of the change log is to show people where to find what was
  changed.  So you need to be specific about what functions you changed; in
  large functions, it's often helpful to indicate where within the function the
  change was.

  On the other hand, once you have shown people where to find the change, you
  need not explain its purpose. Thus, if you add a new function, all you need
  to say about it is that it is new.  If you feel that the purpose needs
  explaining, it probably does---but the explanation will be much more useful
  if you put it in comments in the code.

  Please read the `ChangeLog' file to see what sorts of information to put in,
  and to learn the style that we use.  If you would like your name to appear in
  the header line showing who made the change, send us the header line.

o When you write the fix, keep in mind that we can't install a change that
  would break other systems.  Please think about what effect your change will
  have if compiled on another type of system.

  Sometimes people send fixes that might be an improvement in general---but it
  is hard to be sure of this.  It's hard to install such changes because we
  have to study them very carefully.  Of course, a good explanation of the
  reasoning by which you concluded the change was correct can help convince us.

  The safest changes are changes to the configuration files for a particular
  machine.  These are safe because they can't create new bugs on other
  machines.

  Please help us keep up with the workload by designing the patch in a form
  that is clearly safe to install.


ΓòÉΓòÉΓòÉ 33.11. How To Get Help with GNU Emacs ΓòÉΓòÉΓòÉ

If you need help installing, using or changing GNU Emacs, there are two ways to
find it:

o Send a message to a suitable network mailing list.  First try
  [e-mail], and if that brings no response, try
  [e-mail].

o Look in the service directory for someone who might help you for a fee. The
  service directory is found in the file named `etc/SERVICE' in the Emacs
  distribution.


ΓòÉΓòÉΓòÉ 34. Command Line Options and Arguments ΓòÉΓòÉΓòÉ

 GNU Emacs supports command line arguments to request various actions when
invoking Emacs.  These are for compatibility with other editors and for
sophisticated activities.  We don't recommend using them for ordinary editing.

 Arguments that are not options specify files to visit.  Emacs visits the
specified files while it starts up.  (The last file name on your command line
is the one you see displayed, but the rest are all there in other buffers.)

 You can use options to specify other things, such as the size and position of
the Emacs window if you are running it under the X Window System.  A few
arguments support advanced usage, like running Lisp functions on files in batch
mode.

 There are two kinds of options: ordinary options and initial options.
Ordinary options can appear in any order and can be intermixed with file names
to visit.  These and file names are called ordinary arguments.  Emacs processes
all of these in the order they are written.  Initial options must come at the
beginning of the command line.


ΓòÉΓòÉΓòÉ 34.1. Ordinary Arguments ΓòÉΓòÉΓòÉ

 Here is a table of the ordinary arguments and options:

`file'
          Visit file using find-file.  See Visiting.

`+linenum file'
          Visit file using find-file, then go to line number linenum in it.

`-l file'
`-load file'
          Load a file file of Lisp code with the function load. See Lisp
          Libraries.

`-f function'
`-funcall function'
          Call Lisp function function with no arguments.

`-insert file'
          Insert the contents of file into the current buffer. This is like
          what M-x insert-buffer does; See Misc File Ops.

`-kill'
          Exit from Emacs without asking for confirmation.


ΓòÉΓòÉΓòÉ 34.2. Initial Options ΓòÉΓòÉΓòÉ

 The initial options are recognized only at the beginning of the command line.
If you use more than one of them, they must appear in the order that they
appear in this table.

`-t device'
          Use device as the device for terminal input and output.

`-d display'
          When running with the X window system, use the display named display
          to make the window that serves as Emacs's terminal.

`-batch'
          Run Emacs in batch mode, which means that the text being edited is
          not displayed and the standard Unix interrupt characters such as C-z
          and C-c continue to have their normal effect.  Emacs in batch mode
          outputs to stdout only what would normally be printed in the echo
          area under program control.

          Batch mode is used for running programs written in Emacs Lisp from
          shell scripts, makefiles, and so on.  Normally the `-l' option or
          `-f' option will be used as well, to invoke a Lisp program to do the
          batch processing.

          `-batch' implies `-q' (do not load an init file).  It also causes
          Emacs to kill itself after all command options have been processed.
          In addition, auto-saving is not done except in buffers for which it
          has been explicitly requested.

`-q'
`-no-init-file'
          Do not load your Emacs init file `~/.emacs'.

`-u user'
`-user user'
          Load user's Emacs init file `~user/.emacs' instead of your own.

 The init file can get access to the values of the command line arguments as
the elements of a list in the variable command-line-args.  (The list contains
only the arguments from the first table above.  Emacs processes the arguments
from the second table before building the list.)  The init file can override
the normal processing of the other arguments by setting this variable.


ΓòÉΓòÉΓòÉ 34.3. Command Argument Example ΓòÉΓòÉΓòÉ

 Here is an example of using Emacs with arguments and options.  It assumes you
have a Lisp program file called `hack-c.el' which, when loaded, performs some
useful operation on current buffer, expected to be a C program.

emacs -batch foo.c -l hack-c -f save-buffer -kill > log

This says to visit `foo.c', load `hack-c.el' (which makes changes in the
visited file), save `foo.c' (note that save-buffer is the function that C-x C-s
is bound to), and then exit to the shell that this command was done with.  The
initial option `-batch' guarantees there will be no problem redirecting output
to `log', because Emacs will not assume that it has a display terminal to work
with.


ΓòÉΓòÉΓòÉ 34.4. Resuming Emacs with Arguments ΓòÉΓòÉΓòÉ

 You can specify ordinary arguments for Emacs when you resume it after a
suspension.  To prepare for this, put the following code in your `.emacs' file
(see Hooks):

(add-hook 'suspend-hook 'resume-suspend-hook)

 As further preparation, you must execute the shell script `emacs.csh' (if you
use CSH as your shell) or `emacs.bash' (if you use BASH as your shell).  These
scripts define an alias named edit, which will resume Emacs give it new command
line arguments such as files to visit.

 Only ordinary arguments work properly when you resume Emacs.  Initial
arguments are not recognized.  It's too late to execute them anyway.

 Note that resuming Emacs (with or without arguments) must be done from within
the shell that is the parent of the Emacs job.  This is why edit is an alias
rather than a program or a shell script.  It is not possible to implement a
resumption command that could be run from other subjobs of the shell; no way to
define a command that could be made the value of EDITOR, for example.
Therefore, this feature does not take the place of the the Emacs Server
feature. See Emacs Server.

 The aliases use the Emacs Server feature if you appear to have a server Emacs
running.  However, they cannot determine this with complete accuracy.  They may
think that a server is still running when in actuality you have killed that
Emacs, because the file `/tmp/.esrv...' still exists.  If this happens, find
that file and delete it.


ΓòÉΓòÉΓòÉ 34.5. Specifying the Display Name ΓòÉΓòÉΓòÉ

 The environment variable DISPLAY tells all X clients where to display their
windows.  Its value is set up by default in ordinary circumstances, when you
start an X server and run jobs locally. Occasionally you may need to specify
the display yourself; for example, if you do a remote login and want to run a
client program remotely, displaying on your local screen.

 With Emacs, the main reason people change the default display is to let them
log into another system, run Emacs on that system, but have the window
displayed at their local terminal.  You might need to use login to another
system because the files you want to edit are there, or because the Emacs
executable file you want to run is there.

 The syntax of the DISPLAY environment variable is:

host:display.screen

where host is the host name of the X Window System server machine, display is
an arbitrarily-assigned number that distinguishes your server (X terminal) from
other servers on the same machine, and screen is a rarely-used field that
allows an X server to control multiple terminal screens.  The period and the
screen field are optional.  If included, screen is usually zero.

 If your host is named `glasperle' and your server is the first (or perhaps the
only) server listed in the configuration, your DISPLAY is `glasperle:0.0'.

 You can specify the display name explicitly when you run Emacs, either by
changing the DISPLAY variable, or with the option `-d display' or `-display
display'.  These are initial options; they must come at the beginning of the
command line. See Initial Options.  Here is an example:

emacs -display glasperle:0 &

 You can inhibit the direct use of X with the `-nw' option.  This is also an
initial option.  This option tells Emacs to display using ordinary ASCII on its
controlling terminal.

 Sometimes, security arrangements prevent a program on a remote system from
displaying on your local system.  In this case, trying to run Emacs produces
messages like:

Xlib:  connection to "glasperle:0.0" refused by server

 You might be able to overcome this problem by using the xhost command on the
local system to give permission for access from your remote machine.


ΓòÉΓòÉΓòÉ 34.6. Font Specification Options ΓòÉΓòÉΓòÉ

 By default, Emacs displays text in the font named `9x15', which makes each
character nine pixels wide and fifteen pixels high.  You can specify a
different font on your command line through the option `-fn name'.  The `-font'
option is a synonym for `-fn'.

 Here is how to specify the font `6x13':

emacs -fn 6x13 &

You can also do this in your `.Xdefaults' file:

emacs.font:      6x13

 Use only fixed width fonts---that is, fonts in which all characters have the
same width.  Emacs cannot yet handle display properly for variable width fonts.
Fixed width fonts include the one named `fixed', and fonts with names in the
form nxn, such as `6x13', `8x13', and `9x15'.  Under the font-naming
conventions in X11 Release 4 or later, any font with `m' or `c' in the eleventh
field of the name is a fixed width font.

 Here's how to use the xlsfonts program to list all the fixed width fonts
available on your system:

xlsfonts -fn '*x*'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-m*'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-c*'

To see what a particular font looks like, use the xfd command. For example:

xfd -fn 6x13

displays the entire font `6x13'.

 While running Emacs, you can set the font of the current frame (see Frame
Parameters) or for a specific kind of text (see Faces).


ΓòÉΓòÉΓòÉ 34.7. Window Color Options ΓòÉΓòÉΓòÉ

 On a color display, you can specify which color to use for various parts of
the Emacs display.  To find out what colors are available on your system, look
at the `/usr/lib/X11/rgb.txt' file.  If you do not specify colors, the default
for the background is white and the default for all other colors is black.

 On a monochrome (black and white) display, the foreground is black, the
background is white, and the border is grey.  You can reverse the foreground
and background colors through the `-r' option or the `reverseVideo' resource.

 Here is a list of the options for specifying colors:

`-fg color'
          Specify the foreground color.

`-bg color'
          Specify the background color.

`-bd color'
          Specify the color of the border of the X window.

`-cr color'
          Specify the color of the Emacs cursor which indicates where point is.

`-ms color'
          Specify the color for the mouse cursor when the mouse is in the Emacs
          window.

 For example, to use a coral mouse cursor and a slate blue text cursor, enter:

emacs -ms coral -cr 'slate blue' &


ΓòÉΓòÉΓòÉ 34.8. Options for Window Geometry ΓòÉΓòÉΓòÉ

 The `-geometry' option controls the size and position of the initial Emacs
frame.  Here is the format for specifying the window geometry:

widthxheight{+-}xoffset{+-}yoffset

where width specifies the number of characters displayed on a line, height
specifies the number of lines displayed, a positive xoffset specifies the
distance from the left side of the screen, a negative xoffset specifies the
distance from the right side of the screen, a positive yoffset specifies the
distance from the top of the screen, and a negative yoffset specifies the
distance from the bottom of the screen.

 Emacs uses the same units as xterm does to interpret the geometry. The width
and height are measured in characters, so a large font creates a larger frame
than a small font.  The xoffset and yoffset are measured in pixels.

 Since the the mode line and the echo area occupy the last 2 lines of the
frame, the height of the initial text window is 2 less than the height
specified in your geometry.

 You do not have to specify all of the fields in the geometry specification.
The default width for Emacs is 80 characters and the default height is 24
characters.  You can omit either the width or the height or both.

 If you omit both xoffset nor yoffset, the window manager decides where to put
the Emacs frame, possibly by letting you place it with the mouse.  For example,
`164x55' specifies a window 164 columns wide, enough for two ordinary width
windows side by side, and 55 lines tall.

 If you start the geometry with an integer, Emacs interprets it as the width.
If you start with an `x' followed by an integer, Emacs interprets it as the
height.  Thus, `81' specifies just the width; `x45' specifies just the height.

 If you start with `+' or `-', that introduces an offset, which means both
sizes are omitted.  Thus, `-3' specifies the xoffset only.  (If you give just
one offset, it is always xoffset.)  `+3-3' specifies both the xoffset and the
yoffset, placing the frame near the bottom left of the screen.

 You can specify a default for any or all of the fields in `.Xdefaults' file,
and then override selected fields through a `-geometry' option.


ΓòÉΓòÉΓòÉ 34.9. Internal and External Borders ΓòÉΓòÉΓòÉ

 An Emacs frame has an internal border and an external border.  The internal
border is an extra strip of the background color around all four edges of the
frame.  Emacs itself adds the internal border.  The external border is added by
the window manager outside the internal border; it may contain various boxes
you can click on to move or iconify the window.

 When you specify the size of the frame, that does not count the borders.  The
frame's position is measured from the outside edge of the external border.

 Use the `-ib n' option to specify an internal border n pixels wide.  The
default is 1.  Use `-b n' to specify the width of the external border (though
the window manager may add to this on certain edges).  The default width of the
external border is 2.


ΓòÉΓòÉΓòÉ 34.10. Icons ΓòÉΓòÉΓòÉ

 Most window managers allow the user to ``iconify'' a frame, removing it from
sight, and leaving a small, distinctive ``icon'' window in its place.  Clicking
on the icon window will make the original frame visible again.  If a user has
many clients running at once, they can avoid cluttering up their screen by
iconifying all but the clients currently in use.

 The `-i' and `-itype' option tells Emacs to use an icon window containing a
picture of the GNU gnu.  If omitted, Emacs lets the window manager choose what
sort of icon to use --- usually just a small rectangle containing the frame's
title.

 The `-iconic' option tells Emacs to begin running as an icon, rather than
opening a frame right away.  In this situation, the icon window provides only
indication that Emacs has started; the usual text frame doesn't appear until
you de-iconify it.


ΓòÉΓòÉΓòÉ 34.11. X Resources ΓòÉΓòÉΓòÉ

 Programs running under the X Window System organize their user options under a
hierarchy of classes and resources.  You can specify default values for these
options in your X resources file, usually named `~/.Xdefaults'.

 Each line in the file specifies a value for one option or for a collection of
related options, for one program or for several programs (perhaps even all
programs).

 Programs define named resources with particular meanings.  They also define
how to group resources into named classes.  For instance, in Emacs, the
`internalBorder' resource controls the width of the internal border, and the
`borderWidth' resource controls the width of the external border.  Both of
these resources are part of the `BorderWidth' class.  Case distinctions are
significant in these names.

 In `~/.Xdefaults', you can specify a value for a single resource on one line,
like this:

emacs.borderWidth: 2

Or you can use a class name to specify the same value for all resources in that
class.  Here's an example:

emacs.BorderWidth: 2

 If you specify a value for a class, it becomes the default for all resources
in that class.  You can specify values for individual resources as well; these
override the class value, for those particular resources.  Thus, this example
specifies 2 as the default width for all borders, but overrides this value with
4 for the external border:

emacs.Borderwidth: 2
emacs.borderwidth: 4

 The order in which the lines appear in the file does not matter. Also,
command-line options always override the X resources file.

 The string `emacs' in the examples above is also a resource name.  It actually
represents the name of the executable file that you invoke to run Emacs.  If
Emacs is installed under a different name, it look for resources under that
name instead of `emacs'.

 You can tell Emacs to use a different name instead of the name of the
executable file, with the option `-rn name'.  Then that Emacs job uses name
instead of `Emacs' to look up all of its option values in the X resource file.

 The resources that name Emacs invocations also belong to a class; its name is
`Emacs'.  To specify options for all Emacs jobs, no matter what name is used to
run them, write `Emacs' instead of `emacs', like this:

Emacs.BorderWidth: 2
Emacs.borderWidth: 4

 The following table lists the resource names that designate options for Emacs,
each with the class that it belongs to:

background (class Background)
          Background color name.

bitmapIcon (class BitMapIcon)
          Use kitchen sink icon if `on', let the window manager choose an icon
          if `off'.

borderColor (class BorderColor)
          Color name for external border.

borderWidth (class BorderWidth)
          Width in pixels of external border.

cursorColor (class Foreground)
          Color name for text cursor (point).

font (class Font)
          Font name for text.

foreground (class Foreground)
          Color name for text.

geometry (class Geometry)
          Window size and position.

iconName (class Title)
          Name to display in icon.

internalBorder (class BorderWidth)
          Width in pixels of internal border.

paneFont (class Font)
          Font name for menu pane titles.

pointerColor (class Foreground)
          Color of mouse cursor.

reverseVideo (class ReverseVideo)
          Switch foreground and background default colors if `on', use colors
          as specified if `off'.

selectionFont (class Font)
          Font name for menu items.

title (class Title)
          Name to display in title bar of initial Emacs frame.


ΓòÉΓòÉΓòÉ 35. Emacs 18 Antinews ΓòÉΓòÉΓòÉ

For those users who live backwards in time, here is information about
downgrading to Emacs version 18.  We hope you will enjoy the greater simplicity
that results from the absence of many Emacs 19 features.


ΓòÉΓòÉΓòÉ 35.1. Packages Removed ΓòÉΓòÉΓòÉ

To reduce the size of the distribution, we have eliminated numerous packages
including GNUS, VC (version control), Hexl (for editing binary files), Edebug,
Emerge, Mpuz, Spook, and Gomoku.

Major modes removed in Emacs 18 include C++ mode, Awk mode, Icon mode, Asm
mode, Makefile mode, Perl mode and SGML mode.

The function enable-flow-control does not exist; see the file `PROBLEMS' in the
Emacs distribution for directions for coping with flow control.

The Calendar feature provided is a very simple one.  All it can do is display
three months, by default centered around the current month. If you give it a
numeric argument, that specifies the number of months forward or back.


ΓòÉΓòÉΓòÉ 35.2. Fundamental Changes ΓòÉΓòÉΓòÉ

Auto save and garbage collection happen only while you are typing, never while
you are idle.  This is to make them more like affectionate pets.  Think of them
as cats that like to sit on your terminal only when you are working there.

Transient Mark mode and Line Number mode are absent in Emacs 18.  If you are an
Emacs user, you are smart enough to keep track of the mark in your head, and
you don't need line numbers because you can search for precisely the text you
want.

There are no menu bars or scroll bars; no faces, text properties or overlays.

There are no minibuffer history commands.

There is only one frame, so the Emacs 19 C-x 5 command series is meaningless.
Instead, C-x 5 in Emacs 18 splits the selected window horizontally (like C-x 3
in Emacs 19).

Another simplification in Emacs 18 is that all input events are characters.
Function keys and arrow keys are represented as sequences of characters; the
terminal-specific Emacs Lisp file for your terminal is responsible for defining
them.  Mouse buttons are defined by a special keymap, mouse-map.  See the file
`x-mouse.el' for how to bind mouse clicks.

Character codes 128 and above always display using `\nnn' notation.  For codes
0 through 31, you can choose between `\nnn' and `^c' by setting the variable
ctl-arrow; but that is the only thing you can specify about how character codes
should display.

You can't refer to files on other machines using special ``magic'' file names.
Instead, you must use the ftp library with commands such as M-x ftp-find-file
and M-x ftp-write-file.

The character for terminating an incremental search is now ESC, not RET as in
Emacs 19.  If you type RET, that searches for a newline; thus, you can insert a
newline in the search string just as you would insert it in the text.


ΓòÉΓòÉΓòÉ 35.3. Key Binding Changes ΓòÉΓòÉΓòÉ

The key for backward-paragraph is now M-[.  The key for forward-paragraph is
now M-].

The command repeat-complex-command is now on C-x ESC.

The register commands have different key bindings:

C-x /
          point-to-register

C-x j
          jump-to-register

C-x x
          copy-to-register

C-x g
          insert-register

C-x r
          copy-rectangle-to-register

The narrowing commands have also been moved:

C-x n
          narrow-to-region

C-x p
          narrow-to-page

C-x w
          widen

And the abbrev commands as well:

C-x C-a
          add-mode-abbrev

C-x +
          add-global-abbrev

C-x C-h
          inverse-add-mode-abbrev

C-x -
          inverse-add-global-abbrev

C-x `
          expand-abbrev

There are no key bindings for the rectangle commands.

C-x a now runs the command append-to-buffer.

The key bindings C-x 4 r and C-x 4 C-o do not exist.

The help commands C-h C-f, C-h C-k and C-h p do not exist in Emacs 18.

The command C-M-l (reposition-window) is absent. Likewise C-M-r
(isearch-backward-regexp).

The ``two column'' commands starting with C-x 6 don't exist in Emacs 18.

The TeX mode bindings of C-c { and C-c } have been moved to M-{ and M-}.
(These commands are up-list and tex-insert-braces; they are the TeX equivalents
of M-( and M-).)


ΓòÉΓòÉΓòÉ 35.4. Incremental Search Changes ΓòÉΓòÉΓòÉ

As mentioned above, the character for terminating an incremental search is now
ESC, not RET as in Emacs 19.  If you type RET, that searches for a newline;
thus, you can insert a newline in the search string just as you would insert it
in the text.

There is no ring of previous search strings in Emacs 18.  You can reuse the
most recent search string, but that's all.

If case-fold-search is non-nil, then incremental search is always
case-insensitive.  Typing an upper-case letter in the search string has no
effect on this.

Spaces in the incremental search string match only spaces.

The meanings of the special search characters are no longer controlled by a
keymap.  Instead, particular variables named search-...-char specify the
character that should have a particular function. For example, C-s repeats the
search because the value of search-repeat-char is ?\C-s.


ΓòÉΓòÉΓòÉ 35.5. Editing Command Changes ΓòÉΓòÉΓòÉ

C-n (next-line) does not check the variable next-line-add-newlines.

The sexp commands such as C-M-f no longer know anything about comments, in
modes such as Lisp mode where the end of a comment is the end of the line.
They treat the text inside a comment as if it were actual code.  If comments
containing unbalanced parentheses cause trouble, you can use the commands C-M-n
and C-M-p, which do ignore comments.

You can't store file names in registers, and there are no frame configurations
at all.  The command M-x string-rectangle does not exist either.

The undo command in Emacs 18 is not careful about where to leave point when you
undo a deletion.  It ends up at one end or the other of the text just
undeleted.  You must be on the lookout for this, and move point appropriately.

Kill commands do nothing useful in read-only buffers.  They just beep.

M-z c in Emacs 18 kills up to but not including the first occurrence of c.  If
c does not occur in the buffer after point, M-z kills the whole rest of the
buffer.

The function erase-buffer is not a command in Emacs 18.  You can call it from a
Lisp program, but not interactively.  The motivation for this is to protect you
from accidentally deleting (not killing) the entire text of a buffer that you
want to keep.  With subsequent changes in even earlier Emacs versions (such as
version 18.54), you might be unable to undo the erase-buffer.

M-x fill-nonuniform-paragraphs and Adaptive Fill mode do not exist.


ΓòÉΓòÉΓòÉ 35.6. Other Brief Notes ΓòÉΓòÉΓòÉ

Outline mode exists only as a major mode, not as a minor mode.

M-! (shell-command) always runs the command synchronously, even if the command
ends with `&'.

Emacs 18 has no special mode for change log files.  It is a good idea to use
Indented Text mode, and specify 8 as the value of the variable left-margin.

The command M-x comment-region does not exist. The command M-x super-apropos
does not exist.

C-x q (kbd-macro-query) now uses C-d to terminate all iterations of the
keyboard macro, rather than ESC.

The M-x setenv command is missing in Emacs 18.

M-$ now uses the Unix spell program instead of the GNU program Ispell.  If the
word around point is a misspelling, it asks you for a replacement.

To check spelling of larger units of text, use M-x spell-region or M-x
spell-buffer.  These commands check all words in the specified piece of text.
For each word that is not correct, they ask you to specify a replacement, and
then replace each occurrence.

M-x gdb still exists in Emacs 18.  M-x dbx exists, but is somewhat different
(use C-h m to find the details).  M-x sdb does not exist at all, but who wants
to use SDB?

In Buffer Menu mode, the commands % and C-o don't work in Emacs 18.  The v
command has been eliminated and merged with the q command, which now exits the
buffer menu, displaying all the buffers that you have marked.

The View commands (such as M-x view-buffer and M-x view-file) now use recursive
edits.  When you exit viewing, the recursive edit returns to its caller.

Emacs 18, like most programs, interprets command line options only when it is
started--not later on.

The variable to control whether files can set local variables is called
inhibit-local-variables.  A non-nil value means ask the user before obeying any
local variables lists.

The user option for controlling use of the eval local variable is now called
inhibit-local-eval.  A non-nil value means to ask the user before obeying any
eval local variable.


ΓòÉΓòÉΓòÉ 35.7. File Handling Changes ΓòÉΓòÉΓòÉ

As mentioned above, you can't refer to files on other machines using special
``magic'' file names.  Instead, you must use the ftp library with commands such
as M-x ftp-find-file and M-x ftp-write-file.

When you run M-x revert-buffer with no prefix argument, if the buffer has an
auto save file more recent that the visited file, revert-buffer asks whether to
revert from the auto save file instead.

When C-x s (save-some-buffers) offers to save each buffer, you have only two
choices: save it, or don't save it.

M-x recover-file turns off Auto Save mode in the current buffer. To turn it on
again, use M-x auto-save-mode.

The command M-x rename-uniquely does not exist; instead, use M-x rename-buffer
and try various names until you find one that isn't in use.  Completion can
make this easier.

The directory name abbreviation feature is gone in Emacs 18.

Emacs 18 has no idea of file truenames, and does not try to detect when you
visit a file via a symbolic link.  You should check manually when you visit a
file, so as to edit it in the directory where it is actually stored.  This way
you can make sure that backup files and change log entries go in the proper
directory.

M-x compare-windows ignores any prefix argument and always considers case and
whitespace differences significant.  As for the other ways of comparing files,
M-x diff and M-x diff-backup, they don't exist at all.


ΓòÉΓòÉΓòÉ 35.8. Mail Changes ΓòÉΓòÉΓòÉ

`%' is now a word-component character in Mail mode.  This is to be compatible
with Text mode.

The variable mail-signature is not meaningful; if you wish to insert your
signature in a mail message, you must type C-c C-w.

Mail aliases expand only when you send the message---never when you type them
in.

Rmail now gets new mail into your primary mail file from `~/mbox' as well as
from your system inbox file.  This is handy if you occasionally check your
newest mail with the mail program; whatever you have looked at and saved with
mail will be brought into Rmail the next time you run Rmail.

The Rmail summary buffer is now much simpler.  Only a few special commands are
available there: n, p, and j for motion, d and u for deletion, and SPC and DEL
for scrolling the message.  To do anything else, you must go to the Rmail
buffer.  Also, changes in the Rmail buffer don't update the summary; to do
that, you must make a new summary.

The Rmail command rmail-resend (accessible via f with a prefix argument in
Emacs 19) does not exist in Emacs 18.  Neither does rmail-retry-failure (M-m in
Emacs 19).

The e command is now ``expunge'', just like x.  To edit the current message,
type w, which works in Emacs 19 as well. If you type e meaning to edit, and it
expunges instead---well, you shouldn't have deleted those messages if you still
wanted them.

The < and b commands have been removed in Emacs 18. Likewise C-M-t
(rmail-summarize-by-topic) and M-x unrmail.  Rmail in Emacs 18 is so good, that
we can't imagine anyone who has tried it would ever wish to use another mail
reader.

The default output file for o is now always the last file that you used with o.
The variable rmail-output-file-alist has no special meaning.

Emacs 18 Rmail does not know anything about Content Length fields in messages.


ΓòÉΓòÉΓòÉ 35.9. C Mode Changes ΓòÉΓòÉΓòÉ

In C mode, the keys M-a and M-e now have their usual meanings: motion by
sentences.  This is useful while editing the comments in a C program, but not
useful for editing code.  We hope this will encourage you to write lots of
comments.

The commands M-x c-up-conditional and M-x c-backslash-region have been removed
entirely in Emacs 18.


ΓòÉΓòÉΓòÉ 35.10. Compilation Changes ΓòÉΓòÉΓòÉ

M-x compile now has a much simpler and faster parser for error messages.
However, it understands fewer different formats for error messages, and is not
as easy to customize.

There is no special mode for compilation buffers.  When you select the
compilation buffer itself, it is just ordinary text.

Speaking of selecting the compilation buffer, you do need to do that from time
to time to see whether the compilation has finished, because Emacs 18 does not
display `Compiling' in the mode line to tell you the compilation is still
going.


ΓòÉΓòÉΓòÉ 35.11. Shell Mode ΓòÉΓòÉΓòÉ

Shell mode in Emacs 18 does nothing special for the keys TAB, M-?, C-a, C-d.
The commands M-x dirs and M-x send-invisible are also gone.

The history commands M-p and so on are not available either; instead, use C-c
C-y (copy-last-shell-input).  This copies the previous bunch of shell input,
and inserts it into the buffer before point.  No final newline is inserted, and
the input copied is not resubmitted until you type RET.

Use C-c C-d to send an ``end of file'' to the shell process.


ΓòÉΓòÉΓòÉ 35.12. Dired Changes ΓòÉΓòÉΓòÉ

For simplicity, Dired in Emacs 18 supports just one kind of mark: the deletion
flag, `*'.  The Emacs 19 Dired commands for flagging files do work in Emacs 18,
but all the other mark-related commands do not.

The Dired subdirectory commands don't exist in Emacs 18.  A Dired buffer can
contain only one directory.  In particular, this means that the variable
dired-listing-switches must not contain the `R' option.  (The `F' option is
also not allowed.)

The commands for using find with Dired have been removed for simplicity, also.

Emacs 18 Dired provides the following commands for manipulating files
immediately, and no others.  All of these commands apply to the file listed on
the current line.

c
          Copies the file described on the current line.  You must supply a
          file name to copy to, using the minibuffer.

f
          Visits the file described on the current line.  It is just like
          typing C-x C-f and supplying that file name.  If the file on this
          line is a subdirectory, f actually causes Dired to be invoked on that
          subdirectory.

G
          Change the group of the file described on the current line.

M
          Change the file mode of the file described on the current line.

o
          Like f, but uses another window to display the file's buffer.  The
          Dired buffer remains visible in the first window.  This is like using
          C-x 4 C-f to visit the file.

O
          Change the owner of the file described on the current line. (On most
          systems, you must be a superuser to do this.)

r
          Renames the file described on the current line.  You must supply a
          file name to rename to, using the minibuffer.

v
          Views the file described on this line using M-x view-file.  Viewing a
          file is like visiting it, but is slanted toward moving around in the
          file conveniently and does not allow changing the file.


ΓòÉΓòÉΓòÉ 36. The GNU Manifesto ΓòÉΓòÉΓòÉ

The GNU Manifesto which appears below was written by Richard Stallman at the
beginning of the GNU project, to ask for participation and support. For the
first few years, it was updated in minor ways to account for developments, but
now it seems best to leave it unchanged as most people have seen it.

Since that time, we have learned about certain common misunderstandings that
different wording could help avoid.  Footnotes help clarify these points.

For up-to-date information about the available GNU software, please see the
latest issue of the GNU's Bulletin.  The list is much too long to include here.


ΓòÉΓòÉΓòÉ 36.1. What's GNU?  Gnu's Not Unix! ΓòÉΓòÉΓòÉ

GNU, which stands for Gnu's Not Unix, is the name for the complete
Unix-compatible software system which I am writing so that I can give it away
free to everyone who can use it. (The wording here was careless.  The intention
was that nobody would have to pay for permission to use the GNU system.  But
the words don't make this clear, and people often interpret them as saying that
copies of GNU should always be distributed at little or no charge.  That was
never the intent; later on, the manifesto mentions the possibility of companies
providing the service of distribution for a profit.  Subsequently I have
learned to distinguish carefully between ``free'' in the sense of freedom and
``free'' in the sense of price.  Free software is software that users have the
freedom to distribute and change.  Some users may obtain copies at no charge,
while others pay to obtain copies---and if the funds help support improving the
software, so much the better.  The important thing is that everyone who has a
copy has the freedom to cooperate with others in using it.)  Several other
volunteers are helping me.  Contributions of time, money, programs and
equipment are greatly needed.

So far we have an Emacs text editor with Lisp for writing editor commands, a
source level debugger, a yacc-compatible parser generator, a linker, and around
35 utilities.  A shell (command interpreter) is nearly completed.  A new
portable optimizing C compiler has compiled itself and may be released this
year.  An initial kernel exists but many more features are needed to emulate
Unix.  When the kernel and compiler are finished, it will be possible to
distribute a GNU system suitable for program development.  We will use TeX as
our text formatter, but an nroff is being worked on.  We will use the free,
portable X window system as well.  After this we will add a portable Common
Lisp, an Empire game, a spreadsheet, and hundreds of other things, plus on-line
documentation.  We hope to supply, eventually, everything useful that normally
comes with a Unix system, and more.

GNU will be able to run Unix programs, but will not be identical to Unix. We
will make all improvements that are convenient, based on our experience with
other operating systems.  In particular, we plan to have longer file names,
file version numbers, a crashproof file system, file name completion perhaps,
terminal-independent display support, and perhaps eventually a Lisp-based
window system through which several Lisp programs and ordinary Unix programs
can share a screen.  Both C and Lisp will be available as system programming
languages.  We will try to support UUCP, MIT Chaosnet, and Internet protocols
for communication.

GNU is aimed initially at machines in the 68000/16000 class with virtual
memory, because they are the easiest machines to make it run on.  The extra
effort to make it run on smaller machines will be left to someone who wants to
use it on them.

To avoid horrible confusion, please pronounce the `G' in the word `GNU' when it
is the name of this project.


ΓòÉΓòÉΓòÉ 36.2. Why I Must Write GNU ΓòÉΓòÉΓòÉ

I consider that the golden rule requires that if I like a program I must share
it with other people who like it.  Software sellers want to divide the users
and conquer them, making each user agree not to share with others.  I refuse to
break solidarity with other users in this way.  I cannot in good conscience
sign a nondisclosure agreement or a software license agreement.  For years I
worked within the Artificial Intelligence Lab to resist such tendencies and
other inhospitalities, but eventually they had gone too far: I could not remain
in an institution where such things are done for me against my will.

So that I can continue to use computers without dishonor, I have decided to put
together a sufficient body of free software so that I will be able to get along
without any software that is not free.  I have resigned from the AI lab to deny
MIT any legal excuse to prevent me from giving GNU away.


ΓòÉΓòÉΓòÉ 36.3. Why GNU Will Be Compatible with Unix ΓòÉΓòÉΓòÉ

Unix is not my ideal system, but it is not too bad.  The essential features of
Unix seem to be good ones, and I think I can fill in what Unix lacks without
spoiling them.  And a system compatible with Unix would be convenient for many
other people to adopt.


ΓòÉΓòÉΓòÉ 36.4. How GNU Will Be Available ΓòÉΓòÉΓòÉ

GNU is not in the public domain.  Everyone will be permitted to modify and
redistribute GNU, but no distributor will be allowed to restrict its further
redistribution.  That is to say, proprietary modifications will not be allowed.
I want to make sure that all versions of GNU remain free.


ΓòÉΓòÉΓòÉ 36.5. Why Many Other Programmers Want to Help ΓòÉΓòÉΓòÉ

I have found many other programmers who are excited about GNU and want to help.

Many programmers are unhappy about the commercialization of system software.
It may enable them to make more money, but it requires them to feel in conflict
with other programmers in general rather than feel as comrades.  The
fundamental act of friendship among programmers is the sharing of programs;
marketing arrangements now typically used essentially forbid programmers to
treat others as friends.  The purchaser of software must choose between
friendship and obeying the law.  Naturally, many decide that friendship is more
important.  But those who believe in law often do not feel at ease with either
choice.  They become cynical and think that programming is just a way of making
money.

By working on and using GNU rather than proprietary programs, we can be
hospitable to everyone and obey the law.  In addition, GNU serves as an example
to inspire and a banner to rally others to join us in sharing. This can give us
a feeling of harmony which is impossible if we use software that is not free.
For about half the programmers I talk to, this is an important happiness that
money cannot replace.


ΓòÉΓòÉΓòÉ 36.6. How You Can Contribute ΓòÉΓòÉΓòÉ

I am asking computer manufacturers for donations of machines and money. I'm
asking individuals for donations of programs and work.

One consequence you can expect if you donate machines is that GNU will run on
them at an early date.  The machines should be complete, ready to use systems,
approved for use in a residential area, and not in need of sophisticated
cooling or power.

I have found very many programmers eager to contribute part-time work for GNU.
For most projects, such part-time distributed work would be very hard to
coordinate; the independently-written parts would not work together. But for
the particular task of replacing Unix, this problem is absent.  A complete Unix
system contains hundreds of utility programs, each of which is documented
separately.  Most interface specifications are fixed by Unix compatibility.  If
each contributor can write a compatible replacement for a single Unix utility,
and make it work properly in place of the original on a Unix system, then these
utilities will work right when put together. Even allowing for Murphy to create
a few unexpected problems, assembling these components will be a feasible task.
(The kernel will require closer communication and will be worked on by a small,
tight group.)

If I get donations of money, I may be able to hire a few people full or part
time.  The salary won't be high by programmers' standards, but I'm looking for
people for whom building community spirit is as important as making money.  I
view this as a way of enabling dedicated people to devote their full energies
to working on GNU by sparing them the need to make a living in another way.


ΓòÉΓòÉΓòÉ 36.7. Why All Computer Users Will Benefit ΓòÉΓòÉΓòÉ

Once GNU is written, everyone will be able to obtain good system software free,
just like air. (This is another place I failed to distinguish carefully between
the two different meanings of ``free''. The statement as it stands is not
false---you can get copies of GNU software at no charge, from your friends or
over the net.  But it does suggest the wrong idea.)

This means much more than just saving everyone the price of a Unix license. It
means that much wasteful duplication of system programming effort will be
avoided.  This effort can go instead into advancing the state of the art.

Complete system sources will be available to everyone.  As a result, a user who
needs changes in the system will always be free to make them himself, or hire
any available programmer or company to make them for him.  Users will no longer
be at the mercy of one programmer or company which owns the sources and is in
sole position to make changes.

Schools will be able to provide a much more educational environment by
encouraging all students to study and improve the system code.  Harvard's
computer lab used to have the policy that no program could be installed on the
system if its sources were not on public display, and upheld it by actually
refusing to install certain programs.  I was very much inspired by this.

Finally, the overhead of considering who owns the system software and what one
is or is not entitled to do with it will be lifted.

Arrangements to make people pay for using a program, including licensing of
copies, always incur a tremendous cost to society through the cumbersome
mechanisms necessary to figure out how much (that is, which programs) a person
must pay for.  And only a police state can force everyone to obey them.
Consider a space station where air must be manufactured at great cost: charging
each breather per liter of air may be fair, but wearing the metered gas mask
all day and all night is intolerable even if everyone can afford to pay the air
bill.  And the TV cameras everywhere to see if you ever take the mask off are
outrageous.  It's better to support the air plant with a head tax and chuck the
masks.

Copying all or parts of a program is as natural to a programmer as breathing,
and as productive.  It ought to be as free.


ΓòÉΓòÉΓòÉ 36.8. Some Easily Rebutted Objections to GNU's Goals ΓòÉΓòÉΓòÉ

``Nobody will use it if it is free, because that means they can't rely on any
support.''

``You have to charge for the program to pay for providing the support.''

If people would rather pay for GNU plus service than get GNU free without
service, a company to provide just service to people who have obtained GNU free
ought to be profitable. (Several such companies now exist.)

We must distinguish between support in the form of real programming work and
mere handholding.  The former is something one cannot rely on from a software
vendor.  If your problem is not shared by enough people, the vendor will tell
you to get lost.

If your business needs to be able to rely on support, the only way is to have
all the necessary sources and tools.  Then you can hire any available person to
fix your problem; you are not at the mercy of any individual. With Unix, the
price of sources puts this out of consideration for most businesses.  With GNU
this will be easy.  It is still possible for there to be no available competent
person, but this problem cannot be blamed on distribution arrangements.  GNU
does not eliminate all the world's problems, only some of them.

Meanwhile, the users who know nothing about computers need handholding: doing
things for them which they could easily do themselves but don't know how.

Such services could be provided by companies that sell just hand-holding and
repair service.  If it is true that users would rather spend money and get a
product with service, they will also be willing to buy the service having got
the product free.  The service companies will compete in quality and price;
users will not be tied to any particular one.  Meanwhile, those of us who don't
need the service should be able to use the program without paying for the
service.

``You cannot reach many people without advertising, and you must charge for the
program to support that.''

``It's no use advertising a program people can get free.''

There are various forms of free or very cheap publicity that can be used to
inform numbers of computer users about something like GNU.  But it may be true
that one can reach more microcomputer users with advertising.  If this is
really so, a business which advertises the service of copying and mailing GNU
for a fee ought to be successful enough to pay for its advertising and more.
This way, only the users who benefit from the advertising pay for it.

On the other hand, if many people get GNU from their friends, and such
companies don't succeed, this will show that advertising was not really
necessary to spread GNU.  Why is it that free market advocates don't want to
let the free market decide this? (The Free Software Foundation raises most of
its funds from a distribution service, although it is a charity rather than a
company.  If no one chooses to obtain copies by ordering the from the FSF, it
will be unable to do its work.  But this does not mean that proprietary
restrictions are justified to force every user to pay.  If a small fraction of
all the users order copies from the FSF, that is sufficient to keep the FSF
afloat.  So we ask users to choose to support us in this way.  Have you done
your part?)

``My company needs a proprietary operating system to get a competitive edge.''

GNU will remove operating system software from the realm of competition. You
will not be able to get an edge in this area, but neither will your competitors
be able to get an edge over you.  You and they will compete in other areas,
while benefiting mutually in this one.  If your business is selling an
operating system, you will not like GNU, but that's tough on you.  If your
business is something else, GNU can save you from being pushed into the
expensive business of selling operating systems.

I would like to see GNU development supported by gifts from many manufacturers
and users, reducing the cost to each. (A group of computer companies recently
pooled funds to support maintenance of the GNU C Compiler.)

``Don't programmers deserve a reward for their creativity?''

If anything deserves a reward, it is social contribution.  Creativity can be a
social contribution, but only in so far as society is free to use the results.
If programmers deserve to be rewarded for creating innovative programs, by the
same token they deserve to be punished if they restrict the use of these
programs.

``Shouldn't a programmer be able to ask for a reward for his creativity?''

There is nothing wrong with wanting pay for work, or seeking to maximize one's
income, as long as one does not use means that are destructive.  But the means
customary in the field of software today are based on destruction.

Extracting money from users of a program by restricting their use of it is
destructive because the restrictions reduce the amount and the ways that the
program can be used.  This reduces the amount of wealth that humanity derives
from the program.  When there is a deliberate choice to restrict, the harmful
consequences are deliberate destruction.

The reason a good citizen does not use such destructive means to become
wealthier is that, if everyone did so, we would all become poorer from the
mutual destructiveness.  This is Kantian ethics; or, the Golden Rule. Since I
do not like the consequences that result if everyone hoards information, I am
required to consider it wrong for one to do so. Specifically, the desire to be
rewarded for one's creativity does not justify depriving the world in general
of all or part of that creativity.

``Won't programmers starve?''

I could answer that nobody is forced to be a programmer.  Most of us cannot
manage to get any money for standing on the street and making faces.  But we
are not, as a result, condemned to spend our lives standing on the street
making faces, and starving.  We do something else.

But that is the wrong answer because it accepts the questioner's implicit
assumption: that without ownership of software, programmers cannot possibly be
paid a cent.  Supposedly it is all or nothing.

The real reason programmers will not starve is that it will still be possible
for them to get paid for programming; just not paid as much as now.

Restricting copying is not the only basis for business in software.  It is the
most common basis because it brings in the most money.  If it were prohibited,
or rejected by the customer, software business would move to other bases of
organization which are now used less often.  There are always numerous ways to
organize any kind of business.

Probably programming will not be as lucrative on the new basis as it is now.
But that is not an argument against the change.  It is not considered an
injustice that sales clerks make the salaries that they now do.  If programmers
made the same, that would not be an injustice either.  (In practice they would
still make considerably more than that.)

``Don't people have a right to control how their creativity is used?''

``Control over the use of one's ideas'' really constitutes control over other
people's lives; and it is usually used to make their lives more difficult.

People who have studied the issue of intellectual property rights carefully
(such as lawyers) say that there is no intrinsic right to intellectual
property.  The kinds of supposed intellectual property rights that the
government recognizes were created by specific acts of legislation for specific
purposes.

For example, the patent system was established to encourage inventors to
disclose the details of their inventions.  Its purpose was to help society
rather than to help inventors.  At the time, the life span of 17 years for a
patent was short compared with the rate of advance of the state of the art.
Since patents are an issue only among manufacturers, for whom the cost and
effort of a license agreement are small compared with setting up production,
the patents often do not do much harm.  They do not obstruct most individuals
who use patented products.

The idea of copyright did not exist in ancient times, when authors frequently
copied other authors at length in works of non-fiction.  This practice was
useful, and is the only way many authors' works have survived even in part.
The copyright system was created expressly for the purpose of encouraging
authorship.  In the domain for which it was invented---books, which could be
copied economically only on a printing press---it did little harm, and did not
obstruct most of the individuals who read the books.

All intellectual property rights are just licenses granted by society because
it was thought, rightly or wrongly, that society as a whole would benefit by
granting them.  But in any particular situation, we have to ask: are we really
better off granting such license?  What kind of act are we licensing a person
to do?

The case of programs today is very different from that of books a hundred years
ago.  The fact that the easiest way to copy a program is from one neighbor to
another, the fact that a program has both source code and object code which are
distinct, and the fact that a program is used rather than read and enjoyed,
combine to create a situation in which a person who enforces a copyright is
harming society as a whole both materially and spiritually; in which a person
should not do so regardless of whether the law enables him to.

``Competition makes things get done better.''

The paradigm of competition is a race: by rewarding the winner, we encourage
everyone to run faster.  When capitalism really works this way, it does a good
job; but its defenders are wrong in assuming it always works this way.  If the
runners forget why the reward is offered and become intent on winning, no
matter how, they may find other strategies---such as, attacking other runners.
If the runners get into a fist fight, they will all finish late.

Proprietary and secret software is the moral equivalent of runners in a fist
fight.  Sad to say, the only referee we've got does not seem to object to
fights; he just regulates them (``For every ten yards you run, you can fire one
shot'').  He really ought to break them up, and penalize runners for even
trying to fight.

``Won't everyone stop programming without a monetary incentive?''

Actually, many people will program with absolutely no monetary incentive.
Programming has an irresistible fascination for some people, usually the people
who are best at it.  There is no shortage of professional musicians who keep at
it even though they have no hope of making a living that way.

But really this question, though commonly asked, is not appropriate to the
situation.  Pay for programmers will not disappear, only become less.  So the
right question is, will anyone program with a reduced monetary incentive?  My
experience shows that they will.

For more than ten years, many of the world's best programmers worked at the
Artificial Intelligence Lab for far less money than they could have had
anywhere else.  They got many kinds of non-monetary rewards: fame and
appreciation, for example.  And creativity is also fun, a reward in itself.

Then most of them left when offered a chance to do the same interesting work
for a lot of money.

What the facts show is that people will program for reasons other than riches;
but if given a chance to make a lot of money as well, they will come to expect
and demand it.  Low-paying organizations do poorly in competition with
high-paying ones, but they do not have to do badly if the high-paying ones are
banned.

``We need the programmers desperately.  If they demand that we stop helping our
neighbors, we have to obey.''

You're never so desperate that you have to obey this sort of demand. Remember:
millions for defense, but not a cent for tribute!

``Programmers need to make a living somehow.''

In the short run, this is true.  However, there are plenty of ways that
programmers could make a living without selling the right to use a program.
This way is customary now because it brings programmers and businessmen the
most money, not because it is the only way to make a living.  It is easy to
find other ways if you want to find them.  Here are a number of examples.

A manufacturer introducing a new computer will pay for the porting of operating
systems onto the new hardware.

The sale of teaching, hand-holding and maintenance services could also employ
programmers.

People with new ideas could distribute programs as freeware, asking for
donations from satisfied users, or selling hand-holding services.  I have met
people who are already working this way successfully.

Users with related needs can form users' groups, and pay dues.  A group would
contract with programming companies to write programs that the group's members
would like to use.

All sorts of development can be funded with a Software Tax:

Suppose everyone who buys a computer has to pay x percent of the price as a
software tax.  The government gives this to an agency like the NSF to spend on
software development.

But if the computer buyer makes a donation to software development himself, he
can take a credit against the tax.  He can donate to the project of his own
choosing---often, chosen because he hopes to use the results when it is done.
He can take a credit for any amount of donation up to the total tax he had to
pay.

The total tax rate could be decided by a vote of the payers of the tax,
weighted according to the amount they will be taxed on.

The consequences:

o The computer-using community supports software development.

o This community decides what level of support is needed.

o Users who care which projects their share is spent on can choose this for
  themselves.

In the long run, making programs free is a step toward the post-scarcity world,
where nobody will have to work very hard just to make a living. People will be
free to devote themselves to activities that are fun, such as programming,
after spending the necessary ten hours a week on required tasks such as
legislation, family counseling, robot repair and asteroid prospecting.  There
will be no need to be able to make a living from programming.

We have already greatly reduced the amount of work that the whole society must
do for its actual productivity, but only a little of this has translated itself
into leisure for workers because much nonproductive activity is required to
accompany productive activity.  The main causes of this are bureaucracy and
isometric struggles against competition.  Free software will greatly reduce
these drains in the area of software production.  We must do this, in order for
technical gains in productivity to translate into less work for us.


ΓòÉΓòÉΓòÉ 37. Glossary ΓòÉΓòÉΓòÉ

Abbrev
          An abbrev is a text string which expands into a different text string
          when present in the buffer.  For example, you might define a short
          word as an abbrev for a long phrase that you want to insert
          frequently.  See Abbrevs.

Aborting
          Aborting means getting out of a recursive edit (q.v.).  The commands
          C-] and M-x top-level are used for this. See Quitting.

Alt
          Alt is the name of a modifier bit which a keyboard input character
          may have.  To make a character Alt, type it while holding down the
          ALT key.  Such characters are given names that start with Alt-
          (usually written A- for short). See User Input.

Auto Fill Mode
          Auto Fill mode is a minor mode in which text that you insert is
          automatically broken into lines of fixed width.  See Filling.

Auto Saving
          Auto saving is the practice of saving the contents of an Emacs buffer
          in a specially-named file, so that the information will not be lost
          if the buffer is lost due to a system error or user error.  See Auto
          Save.

Backup File
          A backup file records the contents that a file had before the current
          editing session.  Emacs makes backup files automatically to help you
          track down or cancel changes you later regret making.  See Backup.

Balance Parentheses
          Emacs can balance parentheses manually or automatically.  Manual
          balancing is done by the commands to move over balanced expressions
          (see Lists).  Automatic balancing is done by blinking the parenthesis
          that matches one just inserted ( see Matching Parens).

Bind
          To bind a key sequence means to give it a binding (q.v.). See
          Rebinding.

Binding
          A key sequence gets its meaning in Emacs by having a binding, which
          is a command (q.v.), a Lisp function that is run when the user types
          that sequence.  See Commands.  Customization often involves rebinding
          a character to a different command function.  The bindings of all key
          sequences are recorded in the keymaps (q.v.).  See Keymaps.

Blank Lines
          Blank lines are lines that contain only whitespace.  Emacs has
          several commands for operating on the blank lines in the buffer.

Buffer
          The buffer is the basic editing unit; one buffer corresponds to one
          piece of text being edited.  You can have several buffers, but at any
          time you are editing only one, the `selected' buffer, though several
          can be visible when you are using multiple windows.  See Buffers.

Buffer Selection History
          Emacs keeps a buffer selection history which records how recently
          each Emacs buffer has been selected.  This is used for choosing a
          buffer to select.  See Buffers.

Button Down Event
          A button down event is the kind of input event generated right away
          when you press a mouse button.  See Mouse Buttons.

C-
          `C' in the name of a character is an abbreviation for Control. See
          User Input.

C-M-
          `C-M-' in the name of a character is an abbreviation for
          Control-Meta.  See User Input.

Case Conversion
          Case conversion means changing text from upper case to lower case or
          vice versa.  See Case, for the commands for case conversion.

Characters
          Characters form the contents of an Emacs buffer; see Text Characters.
          Also, key sequences (q.v.) are usually made up of characters (though
          they may include other input events as well). See User Input.

Click Event
          A click event is the kind of input event generated when you press a
          mouse button and let it go without moving the mouse.  See Mouse
          Buttons.

Command
          A command is a Lisp function specially defined to be able to serve as
          a key binding in Emacs.  When you type a key sequence (q.v.), its
          binding (q.v.) is looked up in the relevant keymaps (q.v.) to find
          the command to run.  See Commands.

Command Name
          A command name is the name of a Lisp symbol which is a command (see
          Commands).  You can invoke any command by its name using M-x (see
          M-x).

Comments
          A comment is text in a program which is intended only for humans
          reading the program, and which is marked specially so that it will be
          ignored when the program is loaded or compiled.  Emacs offers special
          commands for creating, aligning and killing comments.  See Comments.

Compilation
          Compilation is the process of creating an executable program from
          source code.  Emacs has commands for compiling files of Emacs Lisp
          code ( see Byte Compilation) and programs in C and other languages
          (see Compilation).

Complete Key
          A complete key is a key sequence which fully specifies one action to
          be performed by Emacs.  For example, X and C-f and C-x m are complete
          keys.  Complete keys derive their meanings from being bound (q.v.) to
          commands (q.v.).  Thus, X is conventionally bound to a command to
          insert `X' in the buffer; C-x m is conventionally bound to a command
          to begin composing a mail message. See Keys.

Completion
          Completion is what Emacs does when it automatically fills out an
          abbreviation for a name into the entire name.  Completion is done for
          minibuffer (q.v.) arguments when the set of possible valid inputs is
          known; for example, on command names, buffer names, and file names.
          Completion occurs when TAB, SPC or RET is typed.  See Completion.

Continuation Line
          When a line of text is longer than the width of the window, it takes
          up more than one screen line when displayed.  We say that the text
          line is continued, and all screen lines used for it after the first
          are called continuation lines. See Basic Editing.

Control Character
          ASCII characters with octal codes 0 through 037, and also code 0177,
          do not have graphic images assigned to them.  These are the Control
          characters.  To type a Control character, hold down the CTRL key and
          type the corresponding non-Control character.  RET, TAB, ESC, LFD and
          DEL are all control characters. See User Input.

          When you are using the X Window System, every non-control character
          has a corresponding control character variant.

Copyleft
          A copyleft is a notice giving the public legal permission to
          redistribute a program or other work of art.  Copylefts are used by
          left-wing programmers to give people equal rights, just as copyrights
          are used by right-wing programmers to gain power over other people.

Current Buffer
          The current buffer in Emacs is the Emacs buffer on which most editing
          commands operate.  You can select any Emacs buffer as the current
          one. See Buffers.

Current Line
          The line point is on (see Point).

Current Paragraph
          The paragraph that point is in.  If point is between paragraphs, the
          current paragraph is the one that follows point.  See Paragraphs.

Current Defun
          The defun (q.v.) that point is in.  If point is between defuns, the
          current defun is the one that follows point.  See Defuns.

Cursor
          The cursor is the rectangle on the screen which indicates the
          position called point (q.v.) at which insertion and deletion takes
          place. The cursor is on or under the character that follows point.
          Often people speak of `the cursor' when, strictly speaking, they mean
          `point'.  See Basic Editing.

Customization
          Customization is making minor changes in the way Emacs works.  It is
          often done by setting variables (see Variables) or by rebinding key
          sequences (see Keymaps).

Default Argument
          The default for an argument is the value that will be assumed if you
          do not specify one.  When the minibuffer is used to read an argument,
          the default argument is used if you just type RET. See Minibuffer.

Default Directory
          When you specify a file name that does not start with `/' or `~', it
          is interpreted relative to the current buffer's default directory.
          See Minibuffer File.

Defun
          A defun is a list at the top level of parenthesis or bracket
          structure in a program.  It is so named because most such lists in
          Lisp programs are calls to the Lisp function defun.  See Defuns.

DEL
          DEL is a character that runs the command to delete one character of
          text.  See Basic Editing.

Deletion
          Deletion means erasing text without copying it into the kill ring
          (q.v.).  The alternative is killing (q.v.).  See Killing.

Deletion of Files
          Deleting a file means erasing it from the file system. See Misc File
          Ops.

Deletion of Messages
          Deleting a message means flagging it to be eliminated from your mail
          file.  Until you expunge (q.v.) the mail file, you can still undelete
          the messages you have deleted.  See Rmail Deletion.

Deletion of Windows
          Deleting a window means eliminating it from the screen.  Other
          windows expand to use up the space.  The deleted window can never
          come back, but no actual text is thereby lost.  See Windows.

Directory
          File directories are named collections in the file system, within
          which you can place individual files or subdirectories. See
          Directories.

Dired
          Dired is the Emacs facility that displays the contents of a file
          directory and allows you to ``edit the directory'', performing
          operations on the files in the directory.  See Dired.

Disabled Command
          A disabled command is one that you may not run without special
          confirmation.  The usual reason for disabling a command is that it is
          confusing for beginning users.  See Disabling.

Down Event
          Short for `button down event'.

Drag Event
          A drag event is the kind of input event generated when you press a
          mouse button, move the mouse, and then release the button. See Mouse
          Buttons.

Dribble File
          A file into which Emacs writes all the characters that the user types
          on the keyboard.  Dribble files are used to make a record for
          debugging Emacs bugs.  Emacs does not make a dribble file unless you
          tell it to.  See Bugs.

Echo Area
          The echo area is the bottom line of the screen, used for echoing the
          arguments to commands, for asking questions, and printing brief
          messages (including error messages).  See Echo Area.

Echoing
          Echoing is acknowledging the receipt of commands by displaying them
          (in the echo area).  Emacs never echoes single-character key
          sequences; longer key sequences echo only if you pause while typing
          them.

Error
          An error occurs when an Emacs command cannot execute in the current
          circumstances.  When an error occurs, execution of the command stops
          (unless the command has been programmed to do otherwise) and Emacs
          reports the error by printing an error message (q.v.).  Type-ahead is
          discarded.  Then Emacs is ready to read another editing command.

Error Messages
          Error messages are single lines of output printed by Emacs when the
          user asks for something impossible to do (such as, killing text
          forward when point is at the end of the buffer).  They appear in the
          echo area, accompanied by a beep.

ESC
          ESC is a character used as a prefix for typing Meta characters on
          keyboards lacking a META key.  Unlike the META key (which, like the
          SHIFT key, is held down while another character is typed), the ESC
          key is pressed once and applies to the next character typed.

Expunging
          Expunging a mail file or Dired buffer means really discarding the
          messages or files you have previously flagged for deletion.

Fill Prefix
          The fill prefix is a string that should be expected at the beginning
          of each line when filling is done.  It is not regarded as part of the
          text to be filled.  See Filling.

Filling
          Filling text means moving text from line to line so that all the
          lines are approximately the same length.  See Filling.

Frame
          A frame is a rectangular cluster of Emacs windows.  When using X
          Windows, you can create more than one Emacs frame, each having its
          own X window, and then you can subdivide each frame into Emacs
          windows as you wish. See Frames.

Function Key
          A function key is a key on the keyboard that does not correspond to
          any character.  See Function Keys.

Global
          Global means `independent of the current environment; in effect
          throughout Emacs'.  It is the opposite of local (q.v.).  Particular
          examples of the use of `global' appear below.

Global Abbrev
          A global definition of an abbrev (q.v.) is effective in all major
          modes that do not have local (q.v.) definitions for the same abbrev.
          See Abbrevs.

Global Keymap
          The global keymap (q.v.) contains key bindings that are in effect
          except when overridden by local key bindings in a major mode's local
          keymap (q.v.).  See Keymaps.

Global Substitution
          Global substitution means replacing each occurrence of one string by
          another string through a large amount of text.  See Replace.

Global Variable
          The global value of a variable (q.v.) takes effect in all buffers
          that do not have their own local (q.v.) values for the variable. See
          Variables.

Graphic Character
          Graphic characters are those assigned pictorial images rather than
          just names.  All the non-Meta (q.v.) characters except for the
          Control (q.v.) characters are graphic characters.  These include
          letters, digits, punctuation, and spaces; they do not include RET or
          ESC.  In Emacs, typing a graphic character inserts that character (in
          ordinary editing modes).  See Basic Editing.

Hardcopy
          Hardcopy means printed output.  Emacs has commands for making printed
          listings of text in Emacs buffers.  See Hardcopy.

HELP
          You can type HELP at any time to ask what options you have, or to ask
          what any command does.  The character HELP is really C-h. See Help.

Hyper
          Hyper is the name of a modifier bit which a keyboard input character
          may have.  To make a character Hyper, type it while holding down the
          HYPER key.  Such characters are given names that start with Hyper-
          (usually written H- for short). See User Input.

Inbox
          An inbox is a file in which mail is delivered by the operating
          system. Rmail transfers mail from inboxes to mail files (q.v.) in
          which the mail is then stored permanently or until explicitly
          deleted. See Rmail Inbox.

Indentation
          Indentation means blank space at the beginning of a line.  Most
          programming languages have conventions for using indentation to
          illuminate the structure of the program, and Emacs has special
          commands to adjust indentation. See Indentation.

Insertion
          Insertion means copying text into the buffer, either from the
          keyboard or from some other place in Emacs.

Justification
          Justification means adding extra spaces to lines of text to make them
          come exactly to a specified width.  See Filling.

Keyboard Macros
          Keyboard macros are a way of defining new Emacs commands from
          sequences of existing ones, with no need to write a Lisp program. See
          Keyboard Macros.

Key Sequence
          A key sequence (key, for short) is a sequence of characters that,
          when input to Emacs, is meaningful as a single unit.  If the key
          sequence is enough to specify one action, it is a complete key
          (q.v.); if it is not enough, it is a prefix key (q.v.).  See Keys.

Keymap
          The keymap is the data structure that records the bindings (q.v.) of
          key sequences to the commands that they run.  For example, the global
          keymap binds the character C-n to the command function next-line.
          See Keymaps.

Keyboard Translation Table
          The keyboard translation table is an array that translates the
          character codes that come from the terminal into the character codes
          that make up key sequences.  See Keyboard Translations.

Kill Ring
          The kill ring is where all text you have killed recently is saved.
          You can reinsert any of the killed text still in the ring; this is
          called yanking (q.v.).  See Yanking.

Killing
          Killing means erasing text and saving it on the kill ring so it can
          be yanked (q.v.) later.  Some other systems call this ``cutting''.
          Most Emacs commands to erase text do killing, as opposed to deletion
          (q.v.).  See Killing.

Killing Jobs
          Killing a job (such as, an invocation of Emacs) means making it cease
          to exist.  Any data within it, if not saved in a file, is lost. See
          Exiting.

List
          A list is, approximately, a text string beginning with an open
          parenthesis and ending with the matching close parenthesis.  In C
          mode and other non-Lisp modes, groupings surrounded by other kinds of
          matched delimiters appropriate to the language, such as braces, are
          also considered lists.  Emacs has special commands for many
          operations on lists.  See Lists.

Local
          Local means `in effect only in a particular context'; the relevant
          kind of context is a particular function execution, a particular
          buffer, or a particular major mode.  It is the opposite of `global'
          (q.v.).  Specific uses of `local' in Emacs terminology appear below.

Local Abbrev
          A local abbrev definition is effective only if a particular major
          mode is selected.  In that major mode, it overrides any global
          definition for the same abbrev.  See Abbrevs.

Local Keymap
          A local keymap is used in a particular major mode; the key bindings
          (q.v.) in the current local keymap override global bindings of the
          same key sequences.  See Keymaps.

Local Variable
          A local value of a variable (q.v.) applies to only one buffer. See
          Locals.

M-
          M- in the name of a character is an abbreviation for META, one of the
          modifier keys that can accompany any character. See User Input.

M-C-
          `M-C-' in the name of a character is an abbreviation for
          Control-Meta; it means the same thing as `C-M-'.  If your terminal
          lacks a real META key, you type a Control-Meta character by typing
          ESC and then typing the corresponding Control character. See User
          Input.

M-x
          M-x is the key sequence which is used to call an Emacs command by
          name.  This is how you run commands that are not bound to key
          sequences. See M-x.

Mail
          Mail means messages sent from one user to another through the
          computer system, to be read at the recipient's convenience.  Emacs
          has commands for composing and sending mail, and for reading and
          editing the mail you have received.  See Sending Mail.  See Rmail,
          for how to read mail.

Mail File
          A mail file is a file which is edited using Rmail and in which Rmail
          stores mail.  See Rmail.

Major Mode
          The Emacs major modes are a mutually exclusive set of options, each
          of which configures Emacs for editing a certain sort of text.
          Ideally, each programming language has its own major mode.  See Major
          Modes.

Mark
          The mark points to a position in the text.  It specifies one end of
          the region (q.v.), point being the other end.  Many commands operate
          on all the text from point to the mark.  Each buffer has its own
          mark. See Mark.

Mark Ring
          The mark ring is used to hold several recent previous locations of
          the mark, just in case you want to move back to them.  Each buffer
          has its own mark ring.  See Mark Ring.

Message
          See `mail'.

Meta
          Meta is the name of a modifier bit which a command character may
          have. It is present in a character if the character is typed with the
          META key held down.  Such characters are given names that start with
          Meta- (usually written M- for short).  For example, M-< is typed by
          holding down META and at the same time typing < (which itself is
          done, on most terminals, by holding down SHIFT and typing ,).  See
          User Input.

Meta Character
          A Meta character is one whose character code includes the Meta bit.

Minibuffer
          The minibuffer is the window that appears when necessary inside the
          echo area (q.v.), used for reading arguments to commands. See
          Minibuffer.

Minibuffer History
          The minibuffer history records the text you have specified in the
          past for minibuffer arguments, so you can conveniently use the same
          text again.  See Minibuffer History.

Minor Mode
          A minor mode is an optional feature of Emacs which can be switched on
          or off independently of all other features.  Each minor mode has a
          command to turn it on or off.  See Minor Modes.

Minor Mode Keymap
          A keymap that belongs to a minor mode and is active when that mode is
          enabled.  Minor mode keymaps take precedence over the buffer's local
          keymap, just as the local keymap takes precedence over the global
          keymap.  See Keymaps.

Mode Line
          The mode line is the line at the bottom of each window (q.v.), giving
          status information on the buffer displayed in that window. See Mode
          Line.

Modified Buffer
          A buffer (q.v.) is modified if its text has been changed since the
          last time the buffer was saved (or since when it was created, if it
          has never been saved).  See Saving.

Moving Text
          Moving text means erasing it from one place and inserting it in
          another.  The usual way to move text by killing (q.v.) and then
          yanking (q.v.).  See Killing.

Named Mark
          A named mark is a register (q.v.) in its role of recording a location
          in text so that you can move point to that location. See Registers.

Narrowing
          Narrowing means creating a restriction (q.v.) that limits editing in
          the current buffer to only a part of the text in the buffer.  Text
          outside that part is inaccessible to the user until the boundaries
          are widened again, but it is still there, and saving the file saves
          it all.  See Narrowing.

Newline
          LFD characters in the buffer terminate lines of text and are called
          newlines.  See Text Characters.

Numeric Argument
          A numeric argument is a number, specified before a command, to change
          the effect of the command.  Often the numeric argument serves as a
          repeat count.  See Arguments.

Option
          An option is a variable (q.v.) that exists so that you can customize
          Emacs by giving it a new value.  See Variables.

Overwrite Mode
          Overwrite mode is a minor mode.  When it is enabled, ordinary text
          characters replace the existing text after point rather than pushing
          it to the right.  See Minor Modes.

Page
          A page is a unit of text, delimited by formfeed characters (ASCII
          control-L, code 014) coming at the beginning of a line.  Some Emacs
          commands are provided for moving over and operating on pages. See
          Pages.

Paragraphs
          Paragraphs are the medium-size unit of English text.  There are
          special Emacs commands for moving over and operating on paragraphs.
          See Paragraphs.

Parsing
          We say that certain Emacs commands parse words or expressions in the
          text being edited.  Really, all they know how to do is find the other
          end of a word or expression.  See Syntax.

Point
          Point is the place in the buffer at which insertion and deletion
          occur.  Point is considered to be between two characters, not at one
          character.  The terminal's cursor (q.v.) indicates the location of
          point.  See Basic.

Prefix Argument
          See `numeric argument'.

Prefix Key
          A prefix key is a key sequence (q.v.) whose sole function is to
          introduce a set of longer key sequences.  C-x is an example of prefix
          key; any two-character sequence starting with C-x is therefore a
          legitimate key sequence.  See Keys.

Primary Mail File
          Your primary mail file is the file named `RMAIL' in your home
          directory, where all mail that you receive is stored by Rmail unless
          you make arrangements to do otherwise.  See Rmail.

Prompt
          A prompt is text printed to ask the user for input.  Printing a
          prompt is called prompting.  Emacs prompts always appear in the echo
          area (q.v.).  One kind of prompting happens when the minibuffer is
          used to read an argument (see Minibuffer); the echoing which happens
          when you pause in the middle of typing a multicharacter key sequence
          is also a kind of prompting (see Echo Area).

Quitting
          Quitting means cancelling a partially typed command or a running
          command, using C-g.  See Quitting.

Quoting
          Quoting means depriving a character of its usual special
          significance. In Emacs this is usually done with C-q.  What
          constitutes special significance depends on the context and on
          convention.  For example, an ``ordinary'' character as an Emacs
          command inserts itself; so in this context, a special character is
          any character that does not normally insert itself (such as DEL, for
          example), and quoting it makes it insert itself as if it were not
          special.  Not all contexts allow quoting.  See Basic Editing.

Read-Only Buffer
          A read-only buffer is one whose text you are not allowed to change.
          Normally Emacs makes buffers read-only when they contain text which
          has a special significance to Emacs; for example, Dired buffers.
          Visiting a file that is write protected also makes a read-only
          buffer. See Buffers.

Recursive Editing Level
          A recursive editing level is a state in which part of the execution
          of a command involves asking the user to edit some text.  This text
          may or may not be the same as the text to which the command was
          applied. The mode line indicates recursive editing levels with square
          brackets (`[' and `]').  See Recursive Edit.

Redisplay
          Redisplay is the process of correcting the image on the screen to
          correspond to changes that have been made in the text being edited.
          See Screen.

Regexp
          See `regular expression'.

Region
          The region is the text between point (q.v.) and the mark (q.v.). Many
          commands operate on the text of the region.  See Mark.

Registers
          Registers are named slots in which text or buffer positions or
          rectangles can be saved for later use.  See Registers.

Regular Expression
          A regular expression is a pattern that can match various text
          strings; for example, `l[0-9]+' matches `l' followed by one or more
          digits.  See Regexps.

Repeat Count
          See `numeric argument'.

Replacement
          See `global substitution'.

Restriction
          A buffer's restriction is the amount of text, at the beginning or the
          end of the buffer, that is temporarily inaccessible.  Giving a buffer
          a nonzero amount of restriction is called narrowing (q.v.). See
          Narrowing.

RET
          RET is a character than in Emacs runs the command to insert a newline
          into the text.  It is also used to terminate most arguments read in
          the minibuffer (q.v.).  See User Input.

Saving
          Saving a buffer means copying its text into the file that was visited
          (q.v.) in that buffer.  This is the way text in files actually gets
          changed by your Emacs editing.  See Saving.

Scrolling
          Scrolling means shifting the text in the Emacs window so as to see a
          different part of the buffer.  See Display.

Searching
          Searching means moving point to the next occurrence of a specified
          string.  See Search.

Selecting
          Selecting a buffer means making it the current (q.v.) buffer. See
          Buffers.

Self-Documentation
          Self-documentation is the feature of Emacs which can tell you what
          any command does, or give you a list of all commands related to a
          topic you specify.  You ask for self-documentation with the help
          character, C-h.  See Help.

Sentences
          Emacs has commands for moving by or killing by sentences. See
          Sentences.

Sexp
          A sexp (short for `s-expression') is the basic syntactic unit of Lisp
          in its textual form: either a list, or Lisp atom.  Many Emacs
          commands operate on sexps.  The term `sexp' is generalized to
          languages other than Lisp, to mean a syntactically recognizable
          expression. See Lists.

Simultaneous Editing
          Simultaneous editing means two users modifying the same file at once.
          Simultaneous editing if not detected can cause one user to lose his
          work.  Emacs detects all cases of simultaneous editing and warns the
          user to investigate them.  See Simultaneous Editing.

String
          A string is a kind of Lisp data object which contains a sequence of
          characters.  Many Emacs variables are intended to have strings as
          values.  The Lisp syntax for a string consists of the characters in
          the string with a `"' before and another `"' after.  A `"' that is
          part of the string must be written as `\"' and a `\' that is part of
          the string must be written as `\\'.  All other characters, including
          newline, can be included just by writing them inside the string;
          however, escape sequences as in C, such as `\n' for newline or `\241'
          using an octal character code, are allowed as well.

String Substitution
          See `global substitution'.

Syntax Table
          The syntax table tells Emacs which characters are part of a word,
          which characters balance each other like parentheses, etc. See
          Syntax.

Super
          Super is the name of a modifier bit which a keyboard input character
          may have.  To make a character Super, type it while holding down the
          SUPER key.  Such characters are given names that start with Super-
          (usually written s- for short). See User Input.

Tag Table
          A tag table is a file that serves as an index to the function
          definitions in one or more other files.  See Tags.

Termscript File
          A termscript file contains a record of all characters sent by Emacs
          to the terminal.  It is used for tracking down bugs in Emacs
          redisplay. Emacs does not make a termscript file unless you tell it
          to. See Bugs.

Text
          Two meanings (see Text):

   o Data consisting of a sequence of characters, as opposed to binary numbers,
     images, graphics commands, executable programs, and the like. The contents
     of an Emacs buffer are always text in this sense.

   o Data consisting of written human language, as opposed to programs, or
     following the stylistic conventions of human language.

Top Level
          Top level is the normal state of Emacs, in which you are editing the
          text of the file you have visited.  You are at top level whenever you
          are not in a recursive editing level (q.v.) or the minibuffer (q.v.),
          and not in the middle of a command.  You can get back to top level by
          aborting (q.v.) and quitting (q.v.).  See Quitting.

Transposition
          Transposing two units of text means putting each one into the place
          formerly occupied by the other.  There are Emacs commands to
          transpose two adjacent characters, words, sexps (q.v.) or lines (see
          Transpose).

Truncation
          Truncating text lines in the display means leaving out any text on a
          line that does not fit within the right margin of the window
          displaying it.  See also `continuation line'. See Basic Editing.

Undoing
          Undoing means making your previous editing go in reverse, bringing
          back the text that existed earlier in the editing session. See Undo.

Variable
          A variable is an object in Lisp that can store an arbitrary value.
          Emacs uses some variables for internal purposes, and has others
          (known as `options' (q.v.)) just so that you can set their values to
          control the behavior of Emacs.  The variables used in Emacs that you
          are likely to be interested in are listed in the Variables Index in
          this manual.  See Variables, for information on variables.

Version Control
          Version control systems keep track of multiple versions of a source
          file. They provide a more powerful alternative to keeping backup
          files (q.v.). See Version Control.

Visiting
          Visiting a file means loading its contents into a buffer (q.v.) where
          they can be edited.  See Visiting.

Whitespace
          Whitespace is any run of consecutive formatting characters (space,
          tab, newline, and backspace).

Widening
          Widening is removing any restriction (q.v.) on the current buffer; it
          is the opposite of narrowing (q.v.).  See Narrowing.

Window
          Emacs divides a frame (q.v.) into one or more windows, each of which
          can display the contents of one buffer (q.v.) at any time. See
          Screen, for basic information on how Emacs uses the screen. See
          Windows, for commands to control the use of windows.

Word Abbrev
          Synonymous with `abbrev'.

Word Search
          Word search is searching for a sequence of words, considering the
          punctuation between them as insignificant.  See Word Search.

Yanking
          Yanking means reinserting text previously killed.  It can be used to
          undo a mistaken kill, or for copying or moving text.  Some other
          systems call this ``pasting''.  See Yanking.


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