OS/2 Professional/OS2PRO194.ISO/os2/prgramer/unix/info/emacs.i05

GNU Info File | 1993-06-14 | 52KB | 861 lines

This is Info file ../info/emacs, produced by Makeinfo-1.47 from the
input file emacs.tex.
   This file documents the GNU Emacs editor.
   Copyright (C) 1985, 1986, 1988 Richard M. Stallman.
   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
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 General Public License" may be included in a
translation approved by the author instead of in the original English.
File: emacs,  Node: Visiting,  Next: Saving,  Prev: File Names,  Up: Files
Visiting Files
==============
`C-x C-f'
     Visit a file (`find-file').
`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 this window.
   "Visiting" a file means copying its contents into Emacs where you can
edit them.  Emacs makes a new buffer for each file that you visit.  We
say that the 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.
*Note Saving::.
   If a buffer contains changes that have not been saved, the buffer is
said to be "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 if 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
   The file name is read using the minibuffer (*note Minibuffer::.),
with defaulting and completion in the standard manner (*note 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 an error results.  The error message is printed in
the echo area, and includes the file name which Emacs was trying to
visit.
   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.  *Note Simultaneous Editing: Interlocking.
   What if you want to create a 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 you visit a nonexistent file unintentionally (because you typed
the wrong file name), use the `C-x C-v' (`find-alternate-file') command
to visit the file you 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).  `C-x C-v' is allowed even if the current buffer is not
visiting a file.
   If the file you specify is actually a directory, Dired is called on
that directory (*note 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.
   `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 before as before, and the other one showing the
newly requested file.  *Note Windows::.
   There are two hook variables that 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'; the value of this
variable is expected to be 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
list of functions and calls them all, one by one.  In both cases the
functions receive no arguments.  Visiting a nonexistent file runs the
`find-file-not-found-hooks' first.
File: emacs,  Node: Saving,  Next: Reverting,  Prev: Visiting,  Up: Files
Saving Files
============
   "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, and record that file
     as the one visited in the buffer (`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') can save any or all
modified buffers.  First it asks, for each modified buffer, whether to
save it. These questions should be answered with `y' or `n'.  `C-x C-c',
the key that kills 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 `save-some-buffers' 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 `Meta-~' 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 undo all the
changes made since the file was visited or saved, by reading the text
from the file again. This is called "reverting".  *Note Reverting::.
You could also undo all the changes by repeating the undo command `C-x
u' until you have undone all the changes; but this only works if you
have not made more changes than the undo mechanism can remember.
   `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.  It can be used on a buffer that is not visiting a file,
too. The buffer's name is changed to correspond to the file it is now
visiting in the usual fashion (unless the new name is in use already
for some other buffer; in that case, the buffer name is not changed).
`set-visited-file-name' does not save the buffer in the newly visited
file; it just alters the records inside Emacs so that, if you save the
buffer, it will be saved in that file.  It also marks the buffer as
"modified" so that `C-x C-s' 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.
*Note Simultaneous Editing: Interlocking.
   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 hook 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.
* Menu:
* Backup::       How Emacs saves the old version of your file.
* Interlocking:: How Emacs protects against simultaneous editing
                  of one file by two users.
File: emacs,  Node: Backup,  Next: Interlocking,  Prev: Saving,  Up: Saving
Backup Files
------------
   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. (Provided 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.
* Menu:
* Names: Backup Names.        How backup files are named;
                Choosing single or numbered backup files.
* Deletion: Backup Deletion.    Emacs deletes excess numbered backups.
* Copying: Backup Copying.    Backups can be made by copying or renaming.
File: emacs,  Node: Backup Names,  Next: Backup Deletion,  Prev: Backup,  Up: Backup
Single or Numbered Backups
..........................
   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
     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.
`version-control' may be set 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.  *Note Locals::.
File: emacs,  Node: Backup Deletion,  Next: Backup Copying,  Prev: Backup Names,  Up: Backup
Automatic Deletion of Backups
.............................
   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 that
control the deletion are `kept-old-versions' and `kept-new-versions'.
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.
*Note Dired::.
File: emacs,  Node: Backup Copying,  Prev: Backup Deletion,  Up: Backup
Copying vs. Renaming
....................
   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'
for them alone (*note File Variables::.).
   The choice of renaming or copying is controlled by three variables.
Normally, renaming is done.  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 done for
files that have multiple names, but renaming may still done when the
file being edited has only one name.  If the variable
`backup-by-copying-when-mismatch' is non-`nil', then copying is done if
renaming would cause the file's owner or group to change.
File: emacs,  Node: Interlocking,  Prev: Backup,  Up: Saving
Protection against Simultaneous Editing
---------------------------------------
   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.  When this is not possible, or if the second user has gone on
to change the file despite the warning, Emacs checks later when the
file is saved, and issues a second warning when a user is about to
overwrite a file containing another user's changes.  If the editing
user takes the proper corrective action at this point, he can prevent
actual loss of work.
   When you make the first modification in an Emacs buffer that is
visiting a file, Emacs records that you have locked the file.  (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 the buffer is modified.  If you begin to modify
the buffer while the visited file is locked by someone else, this
constitutes a collision, and Emacs asks you what to do.  It does this
by calling the Lisp function `ask-user-about-lock', which you can
redefine for the sake of customization.  The standard definition of
this function asks you a question and accepts three possible answers:
     Steal the lock.  Whoever was already changing the file loses the
     lock, and you gain the lock.
     Proceed.  Go ahead and edit the file despite its being locked by
     someone else.
     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 user 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 it in time to prevent you from overwriting someone else's
changes.
   Every time Emacs saves a buffer, it first checks the
last-modification date of the existing file on disk to see 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' (*note Directory Listing: ListDir.).  This will show 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 problem earlier, when perhaps correction takes less work.
File: emacs,  Node: Reverting,  Next: Auto Save,  Prev: Saving,  Up: Files
Reverting a Buffer
==================
   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'.
   If the current buffer has been auto-saved more recently than it has
been saved for real, `revert-buffer' offers to read the auto save file
instead of the visited file (*note Auto Save::.).  This question comes
before the usual request for confirmation, and demands `y' or `n' as an
answer.  If you have started to type `yes' for confirmation without
realizing that the other question was going to be asked, the `y' will
answer that question, but the `es' will not be valid confirmation.  So
you will have a chance to cancel the operation with `C-g' and try it
again with the answers that you really intend.
   `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.
   A buffer reverted from its visited file is marked "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.
File: emacs,  Node: Auto Save,  Next: ListDir,  Prev: Reverting,  Up: Files
Auto-Saving: Protection Against Disasters
=========================================
   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.
* Menu:
* Files: Auto Save Files.
* Control: Auto Save Control.
* Recover::        Recovering text from auto-save files.
File: emacs,  Node: Auto Save Files,  Next: Auto Save Control,  Prev: Auto Save,  Up: Auto Save
Auto-Save Files
---------------
   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' would be 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.
File: emacs,  Node: Auto Save Control,  Next: Recover,  Prev: Auto Save Files,  Up: Auto Save
Controlling Auto-Saving
-----------------------
   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; *note 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.  Emacs also auto-saves
whenever you call the function `do-auto-save'.
   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.
File: emacs,  Node: Recover,  Prev: Auto Save Control,  Up: Auto Save
Recovering Data from Auto-Saves
-------------------------------
   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
     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.
   Auto-saving is disabled by `M-x recover-file' because using this
command implies that the auto-save file contains valuable data from a
past session.  If you save the data in the visited file and then go on
to make new changes, you should turn auto-saving back on with `M-x
auto-save-mode'.
File: emacs,  Node: ListDir,  Next: Dired,  Prev: Auto Save,  Up: Files
Listing a File Directory
========================
   Files are classified by Unix 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 print 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).
File: emacs,  Node: Dired,  Next: Misc File Ops,  Prev: ListDir,  Up: Files
Dired, the Directory Editor
===========================
   Dired makes it easy to delete or visit many of the files in a single
directory at once.  It makes an Emacs buffer containing a listing of the
directory.  You can use the normal Emacs commands to move around in this
buffer, and special Dired commands to operate on the files.
* Menu:
* Enter: Dired Enter.         How to invoke Dired.
* Edit: Dired Edit.           Editing the Dired buffer.
* Deletion: Dired Deletion.   Deleting files with Dired.
* Immed: Dired Immed.         Other file operations through Dired.
File: emacs,  Node: Dired Enter,  Next: Dired Edit,  Prev: Dired,  Up: Dired
Entering Dired
--------------
   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
just like the `list-directory' command, `C-x C-d'.  Where `dired'
differs from `list-directory' is in naming the buffer after the
directory name or the wildcard pattern used for the listing, and putting
the buffer into Dired mode so that the special commands of Dired are
available in it.  The variable `dired-listing-switches' is a string
used as an argument to `ls' in making the directory; this string must
contain `-l'.
   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
File: emacs,  Node: Dired Edit,  Next: Dired Deletion,  Prev: Dired Enter,  Up: Dired
Editing in Dired
----------------
   Once the Dired buffer exists, you can switch freely between it and
other Emacs buffers.  Whenever the Dired buffer is selected, certain
special commands are provided that operate on files that are listed.
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 Dired commands.  Most Dired commands operate on the file described
by the line that point is on.  Some commands perform operations
immediately; others "flag" the file to be operated on later.
   Most Dired commands that operate on the current line's file also
treat a numeric argument as a repeat count, meaning to act on the files
of the next few lines.  A negative argument means to operate on the
files of the preceding lines, and leave point on the first of those
lines.
   All the usual Emacs cursor motion commands are available in Dired
buffers.  Some special purpose commands are also provided.  The keys
`C-n' and `C-p' are redefined so that they try to position the cursor
at the beginning of the filename 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 done so often in Dired
that it deserves to be easy to type.  DEL (move up and unflag) is often
useful simply for moving up.
   The `g' command in Dired runs `revert-buffer' to reinitialize the
buffer from the actual disk directory and show any changes made in the
directory by programs other than Dired.  All deletion flags in the Dired
buffer are lost when this is done.
File: emacs,  Node: Dired Deletion,  Next: Dired Immed,  Prev: Dired Edit,  Up: Dired
Deleting Files with Dired
-------------------------
   The primary use of Dired is to flag files for deletion and then
delete them.
     Flag this file for deletion.
     Remove deletion-flag on this line.
`DEL'
     Remove deletion-flag on previous line, moving point to that line.
     Delete the files that are flagged for deletion.
     Flag all auto-save files (files whose names start and end with `#')
     for deletion (*note Auto Save::.).
     Flag all backup files (files whose names end with `~') for deletion
     (*note 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.
   You can flag a file for deletion by moving to the line describing the
file and typing `d' or `C-d'.  The deletion flag is visible as a `D' at
the beginning of the line.  Point is moved 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
avoid the danger of deleting a file accidentally.  Until you direct
Dired to delete 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'.  This command first displays a
list of all the file names flagged for deletion, and requests
confirmation with `yes'.  Once you confirm, all the flagged files are
deleted, and their lines are deleted from the text of the Dired buffer.
 The shortened Dired buffer remains selected.  If you answer `no' or
quit with `C-g', you return immediately to Dired, with the deletion
flags still present and no files actually deleted.
   The `#', `~' and `.' commands flag many files for deletion, based on
their 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 that appear to have been made by
auto-saving (that is, files whose names begin and end with `#'). `~'
flags for deletion all files that appear to have been made as backups
for files that were edited (that is, files whose names end with `~').
   `.' (Period) flags just some of the backup files for deletion: only
numeric backups that are not among the oldest few nor the 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.
File: emacs,  Node: Dired Immed,  Prev: Dired Deletion,  Up: Dired
Immediate File Operations in Dired
----------------------------------
   Some file operations in Dired take place immediately when they are
requested.
     Copies the file described on the current line.  You must supply a
     file name to copy to, using the minibuffer.
     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.  *Note Visiting::.
     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.  *Note Windows::.
     Renames the file described on the current line.  You must supply a
     file name to rename to, using the minibuffer.
     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.  *Note View File: Misc File Ops.  Viewing a file that is a
     directory runs Dired on that directory.
File: emacs,  Node: Misc File Ops,  Prev: Dired,  Up: Files
Miscellaneous File Operations
=============================
   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' reads and displays
one windowful.  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'.
   `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.  *Note Mark::.
   `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.
   `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 (*note 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, and
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. Confirmation is
required when creating the link if LINKNAME is in use.  Note that not
all systems support symbolic links.
File: emacs,  Node: Buffers,  Next: Windows,  Prev: Files,  Up: Top
Using Multiple Buffers
**********************
   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 makes 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
(*note 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
(*note 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.  *Note Locals::.
* Menu:
* Select Buffer::   Creating a new buffer or reselecting an old one.
* List Buffers::    Getting a list of buffers that exist.
* Misc Buffer::     Renaming; changing read-onliness; copying text.
* Kill Buffer::     Killing buffers you no longer need.
* Several Buffers:: How to go through the list of all buffers
                     and operate variously on several of them.
File: emacs,  Node: Select Buffer,  Next: List Buffers,  Prev: Buffers,  Up: Buffers
Creating and Selecting Buffers
==============================
`C-x b BUFFER RET'
     Select or create a buffer named BUFFER (`switch-to-buffer').
`C-x 4 b BUFFER RET'
     Similar but select a buffer named BUFFER in another window
     (`switch-to-buffer-other-window').
   To select the buffer named BUFNAME, type `C-x b BUFNAME RET'.  This
is the command `switch-to-buffer' with argument BUFNAME.  You can use
completion on an abbreviation for the buffer name you want (*note
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' (*note Major Modes::.).
   Note that `C-x C-f', and any other command for visiting a file, can
also be used to switch buffers.  *Note Visiting::.
File: emacs,  Node: List Buffers,  Next: Misc Buffer,  Prev: Select Buffer,  Up: Buffers
Listing Existing Buffers
========================
`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.
`*' 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'
(*note 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
         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/'.
File: emacs,  Node: Misc Buffer,  Next: Kill Buffer,  Prev: List Buffers,  Up: Buffers
Miscellaneous Buffer Operations
===============================
`C-x C-q'
     Toggle read-only status of buffer (`toggle-read-only').
`M-x rename-buffer'
     Change the name of the current buffer.
`M-x view-buffer'
     Scroll through a buffer.
   A buffer can be "read-only", which means that commands to change its
text are not allowed.  Normally, read-only buffers are made by
subsystems such as Dired and Rmail that have special commands to
operate on the text; a read-only buffer is also made 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'
(`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'.
   `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 view-buffer' is much like `M-x view-file' (*note 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 `C-x a' (`append-to-buffer') and `M-x insert-buffer'
can be used to copy text from one buffer to another. *Note Accumulating
Text::.
File: emacs,  Node: Kill Buffer,  Next: Several Buffers,  Prev: Misc Buffer,  Up: Buffers
Killing Buffers
===============
   After you use Emacs for a while, you may accumulate a large number of
buffers.  You may then find it convenient to eliminate the ones you no
longer need.  There are several commands provided for doing this.
`C-x k'
     Kill a buffer, specified by name (`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 the current buffer is
killed, another buffer is selected; a buffer that has been selected
recently but does not appear in any window now is chosen to be selected.
If the buffer being killed is modified (has unsaved editing) then you
are asked to 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'.
File: emacs,  Node: Several Buffers,  Prev: Kill Buffer,  Up: Buffers
Operating on Several Buffers
============================
   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 only be changed through the
special commands described in this section.  Most of these commands are
graphic characters.  The usual Emacs cursor motion commands can be used
in the `*Buffer List*' buffer.  The following special commands apply to
the buffer described on the current line.
     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 the `x' command is used.
     Synonym for `d'.
`C-d'
     Like `d' but move up afterwards instead of down.
     Request to save the buffer.  The request shows as an `S' on the
     line.  Requested saves take place when the `x' command is used.
     You may request both saving and deletion for the same buffer.
     Mark buffer "unmodified".  The command `~' does this immediately
     when typed.
     Perform previously requested deletions and saves.
     Remove any request made for the current line, and move down.
`DEL'
     Move to previous line and remove any request made for that line.
   All the commands that put in or remove flags to request later
operations also move down a line, and accept a numeric argument as a
repeat count, unless otherwise specified.
   There are also special commands to use the buffer list to select
another buffer, and to specify one or more other buffers for display in
additional windows.
     Select the buffer in a full-screen window.  This command takes
     effect immediately.
     Immediately set up two windows, with this buffer in one, and the
     previously selected buffer (aside from the buffer `*Buffer List*')
     in the other.
     Immediately select the buffer in place of the `*Buffer List*'
     buffer.
     Immediately select the buffer in another window as if by `C-x 4 b',
     leaving `*Buffer List*' visible.
     Immediately select this buffer, and also display in other windows
     any buffers previously flagged with the `m' command.  If there are
     no such buffers, this command is equivalent to `1'.
     Flag this 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.
   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.