InfoMagic Source Code 1993 July/THE_SOURCE_CODE_CD_ROM.iso/msdos/demacs/info/emacs.6

Text File | 1991-12-09 | 54.3 KB | 1,208 lines

Info file emacs, produced by texinfo-format-buffer   -*-Text-*-
from file emacs.tex

This file documents the GNU Emacs editor.

Copyright (C) 1985, 1986 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 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 author instead of in the original English.


File: emacs  Node: Just Spaces, Prev: Tab Stops, Up: Indentation

Tabs vs. Spaces
===============

  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.  *Note 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.


File: emacs  Node: Text, Prev: Indentation, Up: Top, Next: Programs

Commands for Human Languages
****************************

  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", or rearranging paragraphs into lines of approximately equal
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.

* Menu:

* Text Mode::   The major modes for editing text files.
* Nroff Mode::  The major mode for editing input to the formatter nroff.
* TeX Mode::    The major modes for editing input to the formatter TeX.
* Outline Mode::The major mode for editing outlines.
* Words::       Moving over and killing words.
* Sentences::   Moving over and killing sentences.
* Paragraphs::    Moving over paragraphs.
* Pages::    Moving over pages.
* Filling::     Filling or justifying text
* Case::        Changing the case of text


File: emacs  Node: Text Mode, Prev: Text, Up: Text, Next: Words

Text Mode
=========

  Editing files of text in a human language ought to be done using Text
mode rather than Lisp or 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' (*Note 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' (*Note 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 calls with no arguments the
value of the variable `text-mode-hook', if that value exists and is
not `nil'.  This value is also called when modes related to Text mode
are entered; this includes Nroff mode, TeX mode, Outline mode and Mail
mode.  Your hook can look at the value of `major-mode' to see which of
these modes is actually being entered.

* Menu:

  Two modes similar to Text mode are of use for editing text that is to
be passed through a text formatter before achieving the form in which
humans are to read it.

* Nroff Mode::  The major mode for editing input to the formatter nroff.
* TeX Mode::    The major modes for editing input to the formatter TeX.

  Another similar mode is used for editing outlines.  It allows you
to view the text at various levels of detail.  You can view either
the outline headings alone or both headings and text; you can also
hide some of the headings at lower levels from view to make the high
level structure more visible.

* Outline Mode::The major mode for editing outlines.


File: emacs  Node: Nroff Mode, Prev: Text Mode, Up: Text Mode, Next: TeX Mode

Nroff Mode
----------

  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 newline mode.  This is a minor mode that you can turn on or off
with `M-x electric-nroff-mode' (*Note 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', the matching command
`.)b' will be inserted on a new line following point.

  Entering Nroff mode calls with no arguments the value of the variable
`text-mode-hook', if that value exists and is not `nil'; then it
does the same with the variable `nroff-mode-hook'.


File: emacs  Node: TeX Mode, Prev: Nroff Mode, Up: Text Mode, Next: Outline Mode

TeX Mode
--------

  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.

  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 two variants, Plain TeX mode and LaTeX mode
(actually two distinct major modes which differ only slightly).  They are
designed for editing the two different input formats.  The command `M-x
tex-mode' looks at the contents of the buffer to determine whether the
contents appear to be LaTeX input or not; 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.

  The commands `M-x plain-tex-mode' and `M-x latex-mode' explicitly select
the two variants of TeX mode.  Use these commands when `M-x tex-mode' does
not guess right.

* Menu:

* Editing: TeX Editing.   Special commands for editing in TeX mode.
* Printing: TeX Print.    Commands for printing part of a file with TeX.

  TeX for Berkeley Unix can be obtained on a 1600bpi tar tape for a $100
distribution fee from

     Pierre MacKay
     Department of Computer Science, FR-35
     University of Washington
     Seattle, WA 98195

It would work on system V as well if that version of Unix had a reasonable
Pascal compiler.  Outside the U.S., add $10 to cover extra costs.


File: emacs  Node: TeX Editing, Prev: TeX Mode, Up: TeX Mode, Next: TeX Print

TeX Editing Commands
....................

  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-buffer'
     Check each paragraph in the buffer for unbalanced braces or dollar signs.
`M-{'
     Insert `{}' and position point between them (`TeX-insert-braces').
`M-}'
     Move forward past the next unmatched close brace (`up-list').
`C-c C-f'
     Close a block for LaTeX (`TeX-close-LaTeX-block').

  In TeX, the character `"' is not normally used; one uses `"'
to start a quotation and `"' to end one.  TeX mode defines the key
`"' to insert `"' after whitespace or an open brace, `"'
after a backslash, or `"' otherwise.  This is done by the command
`TeX-insert-quote'.  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.

  If you prefer to keep braces balanced at all times, you can use `M-{'
(`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 `M-}' (`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-buffer' checks
the entire buffer, 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 (*Note Mark Ring::).

  Note that square brackets and parentheses are matched in TeX mode, not
just braces.  This is wrong 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.

  In LaTeX input, `\begin' and `\end' commands must balance.  After you
insert a `\begin', use `C-c C-f' (`TeX-close-LaTeX-block') to insert
automatically a matching `\end' (on a new line following the `\begin').  A
blank line is inserted between the two, and point is left there.


File: emacs  Node: TeX Print, Prev: TeX Editing, Up: TeX Mode

TeX Printing Commands
.....................

  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, plus the buffer's header
     (`TeX-region').
`C-c C-b'
     Invoke TeX on the entire current buffer (`TeX-buffer').
`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 inferior TeX (`TeX-kill-job').
`C-c C-p'
     Print the output from the last `C-c C-r' or `C-c C-b' command
     (`TeX-print').
`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 file
in `/tmp'; 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.

  The console output from TeX, including any error messages, appear 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;
*Note 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.

  Entering either kind of TeX mode calls with no arguments the value of
the variable `text-mode-hook', if that value exists and is not
`nil'; then it does the same with the variable `TeX-mode-hook'.
Finally it does the same with either `plain-TeX-mode-hook' or
`LaTeX-mode-hook'.


File: emacs  Node: Outline Mode, Prev: TeX Mode, Up: Text Mode

Outline Mode
------------

  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 turn on Outline mode in the current buffer.

  Entering Outline mode calls with no arguments the value of the variable
`text-mode-hook', if that value exists and is not `nil'; then it
does the same with the variable `outline-mode-hook'.

  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.

* Menu:

* Format: Outline Format.      What the text of an outline looks like.
* Motion: Outline Motion.      Special commands for moving through outlines.
* Visibility: Outline Visibility. Commands to control what is visible.


File: emacs  Node: Outline Format, Prev: Outline Mode, Up: Outline Mode, Next: Outline Motion

Format of Outlines
..................

  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 to 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.


File: emacs  Node: Outline Motion, Prev: Outline Format, Up: Outline Mode, Next: Outline Visibility

Outline Motion Commands
.......................

  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 advanced motion commands understand the levels 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.


File: emacs  Node: Outline Visibility, Prev: Outline Motion, Up: Outline Mode

Outline Visibility Commands
...........................

  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.

  The use of ellipses at the ends of visible lines can be turned off
by setting `selective-display-ellipses' to `nil'.  Then there
is no visible indication of the presence of invisible lines.


File: emacs  Node: Words, Prev: Text Mode, Up: Text, Next: Sentences

Words
=====

  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;  drag a word forward
     or backward 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 `Meta-f' (`forward-word') and `Meta-b' (`backward-word')
move forward and backward over words.  They are thus analogous to
`Control-f' and `Control-b', which move over single characters.  Like their
`Control-' analogues, `Meta-f' and `Meta-b' move several words if given an
argument.  `Meta-f' with a negative argument moves backward, and `Meta-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.

  `Meta-d' (`kill-word') kills the word after point.  To be
precise, it kills everything from point to the place `Meta-f' would
move to.  Thus, if point is in the middle of a word, `Meta-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 `Meta-f' to get
the end, and kill the word backwards with `Meta-DEL'.)
`Meta-d' takes arguments just like `Meta-f'.

  `Meta-DEL' (`backward-kill-word') kills the word before
point.  It kills everything from point back to where `Meta-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
`Meta-b Meta-d' instead of `Meta-DEL'.)

  `Meta-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,'.  *Note 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 `Meta-@' (`mark-word')
which does not move point, but sets the mark where `Meta-f' would move
to.  It can be given arguments just like `Meta-f'.

  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.  *Note Syntax::.


File: emacs  Node: Sentences, Prev: Words, Up: Text, Next: Paragraphs

Sentences
=========

  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 `Meta-a' and `Meta-e' (`backward-sentence' and
`forward-sentence') move to the beginning and end of the current sentence,
respectively.  They were chosen to resemble `Control-a' and `Control-e',
which move to the beginning and end of a line.  Unlike them, `Meta-a' and
`Meta-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.  *Note Regexps::.


File: emacs  Node: Paragraphs, Prev: Sentences, Up: Text, Next: Pages

Paragraphs
==========

  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').

  `Meta-[' moves to the beginning of the current or previous paragraph,
while `Meta-]' 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.  *Note Filling::.

  When you wish to operate on a paragraph, you can use the command
`Meta-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.


File: emacs  Node: Pages, Prev: Paragraphs, Up: Text, Next: Filling

Pages
=====

  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.  It can be inserted with `C-q
C-l', or deleted with DEL.  Thus, you are free to paginate your file
or not.  However, since pages are often meaningful divisions of the file,
commands are provided 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' should have as its value a regexp that
matches the beginning of a line that separates pages.  This is what defines
where pages begin.  The normal value of this variable is `"^\f"',
which matches a formfeed character at the beginning of a line.


File: emacs  Node: Filling, Prev: Pages, Up: Text, Next: Case

Filling Text
============

  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 explicit commands for filling can be
used.

* Menu:

* Auto Fill::      Auto Fill mode breaks long lines automatically.
* Fill Commands:: Commands to refill paragraphs and center lines.
* Fill Prefix::   Filling when every line is indented or in a comment, etc.


File: emacs  Node: Auto Fill, Prev: Filling, Up: Filling, Next: Fill Commands

Auto Fill Mode
--------------


  "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.  *Note 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 (*Note 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.

  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.
*Note Init File::.


File: emacs  Node: Fill Commands, Prev: Auto Fill, Up: Filling, Next: Fill Prefix

Explicit Fill Commands
----------------------

`M-q'
     Fill current paragraph (`fill-paragraph').
`M-g'
     Fill each paragraph in the region (`fill-region').
`C-x f'
     Set the fill column (`set-fill-column').
`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 `Meta-q' (`fill-paragraph').  It
causes the paragraph that point is inside, or the one after point if point
is between paragraphs, to be refilled.  All the line-breaks are removed,
and then new ones are inserted where necessary.  `M-q' can be undone with
`C-_'.  *Note Undo::.

  To refill many paragraphs, use `M-g' (`fill-region'), which
divides the region into paragraphs and fills each of them.

  `Meta-q' and `Meta-g' use the same criteria as `Meta-h' for finding
paragraph boundaries (*Note Paragraphs::).  For more control, you can use
`M-x fill-region-as-paragraph', which refills everything between point and
mark.  This command recognizes only blank lines as paragraph separators.

  A numeric argument to `M-g' or `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' or `M-g' with no argument.

  The command `Meta-s' (`center-line') centers the current line
within the current fill column.  With an argument, it centers several lines
individually and moves past them.

  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.  *Note 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.


File: emacs  Node: Fill Prefix, Prev: Fill Commands, Up: Filling

The Fill Prefix
---------------

  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.

  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.

  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.  *Note Locals::.

  Another way to use fill prefixes is through `M-x
fill-individual-paragraphs'.  This function divides the region into groups
of consecutive lines with the same amount and kind of indentation and fills
each group as a paragraph using its indentation as a fill prefix.


File: emacs  Node: Case, Prev: Filling, Up: Text

Case Conversion Commands
========================

  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.  `Meta-l'
(`downcase-word') converts the word after point to lower case, moving
past it.  Thus, repeating `Meta-l' converts successive words.
`Meta-u' (`upcase-word') converts to all capitals instead, while
`Meta-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 `Meta-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.


File: emacs  Node: Programs, Prev: Text, Up: Top, Next: Running

Editing Programs
****************

  Emacs has many commands designed to understand the syntax of programming
languages such as Lisp and C.  These commands can

   * Move over or kill balanced expressions or "sexps" (*Note Lists::).
   * Move over or mark top-level balanced expressions ("defuns", in Lisp;
     functions, in C).
   * Show how parentheses balance (*Note Matching::).
   * Insert, kill or align comments (*Note Comments::).
   * Follow the usual indentation conventions of the language
     (*Note Grinding::).

  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 (*Note Words::); sentences can
be found in strings and comments (*Note Sentences::).  Paragraphs per se
are not present in code, but the paragraph commands are useful anyway,
because Lisp mode and C mode define paragraphs to begin and end at blank
lines (*Note 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 (*Note Selective Display::).  This feature causes
only the lines that are indented less than a specified amount to appear
on the screen.

* Menu:

* Program Modes::       Major modes for editing programs.
* Lists::               Expressions with balanced parentheses.
                         There are editing commands to operate on them.
* Defuns::              Each program is made up of separate functions.
                         There are editing commands to operate on them.
* Grinding::            Adjusting indentation to show the nesting.
* Matching::            Insertion of a close-delimiter flashes matching open.
* Comments::            Inserting, illing and aligning comments.
* Balanced Editing::    Inserting two matching parentheses at once, etc.
* Lisp Completion::     Completion on symbol names in Lisp code.
* Documentation::       Getting documentation of functions you plan to call.
* Change Log::          Maintaining a change history for your program.
* Tags::                Go direct to any function in your program in one
                         command.  Tags remembers which file it is in.
* Fortran::        Fortran mode and its special features.


File: emacs  Node: Program Modes, Prev: Programs, Up: Programs, Next: Lists

Major Modes for Programming Languages
=====================================

  Emacs also has major modes for the programming languages Lisp, Scheme (a
variant of Lisp), C, Fortran and Muddle.  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.  *Note Lisp Modes::.

  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 calls a user-supplied function called the "mode
hook", which is the value of a Lisp variable.  For example, turning on C
mode calls the value of the variable `c-mode-hook' if that value exists and
is non-`nil'.  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'.
The mode hook function receives no arguments.


File: emacs  Node: Lists, Prev: Program Modes, Up: Programs, Next: Defuns

Lists and Sexps
===============

  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 English).

  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
sexp in C mode.

  Some languages have obscure forms of syntax for expressions that nobody
has bothered to make Emacs understand properly.

`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.  If the character after point is a closing delimiter, `C-M-f' just
moves past it.  (This last is not really moving across a sexp; it is an
exception which is included in the definition of `C-M-f' because it is as
useful a behavior as anyone can think of for that situation.)

  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 (singlequote,
backquote and comma, in Lisp) preceding the sexp, `C-M-b' moves back
over them as well.

  `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.

  The sexp commands move across comments as if they were whitespace, in
languages such as C where the comment-terminator can be recognized.  In
Lisp, and other languages where comments run until the end of a line, it is
very difficult to ignore comments when parsing backwards; therefore, in
such languages the sexp commands treat the text of comments as if it were
code.

  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 easy to use 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.
*Note Syntax::.