This is ../../info/emacs, produced by makeinfo version 4.13 from
emacs.texi.

This is the Sixteenth edition of the `GNU Emacs Manual',
updated for Emacs version 23.4.

   Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
2011, 2012  Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.3 or any later version published by the Free Software
     Foundation; with the Invariant Sections being "The GNU Manifesto,"
     "Distribution" and "GNU GENERAL PUBLIC LICENSE," with the
     Front-Cover texts being "A GNU Manual," and with the Back-Cover
     Texts as in (a) below.  A copy of the license is included in the
     section entitled "GNU Free Documentation License."

     (a) The FSF's Back-Cover Text is: "You have the freedom to copy and
     modify this GNU manual.  Buying copies from the FSF supports it in
     developing GNU and promoting software freedom."

INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Emacs: (emacs).       The extensible self-documenting text editor.
END-INFO-DIR-ENTRY


File: emacs,  Node: Nonincremental Search,  Next: Word Search,  Prev: Incremental Search,  Up: Search

19.2 Nonincremental Search
==========================

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

`C-s <RET> STRING <RET>'
     Search for STRING.

`C-r <RET> STRING <RET>'
     Search backward for STRING.

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

   When you type `C-s <RET>', the `C-s' invokes incremental search as
usual.  That command is specially programmed to invoke nonincremental
search, `search-forward', if the string you specify is empty.  (Such an
empty argument would otherwise be useless.)  `C-r <RET>' does likewise,
for a reverse incremental search.

   Forward and backward nonincremental searches are implemented by the
commands `search-forward' and `search-backward'.  These commands may be
bound to other keys in the usual manner.


File: emacs,  Node: Word Search,  Next: Regexp Search,  Prev: Nonincremental Search,  Up: Search

19.3 Word Search
================

A "word search" finds a sequence of words without regard to the type of
punctuation between them.  For instance, if you enter a search string
that consists of two words separated by a single space, the search
matches any sequence of those two words separated by one or more
spaces, newlines, or other punctuation characters.  This is
particularly useful for searching text documents, because you don't
have to worry whether the words you are looking for are separated by
newlines or spaces.

`M-s w'
     If incremental search is active, toggle word search mode
     (`isearch-toggle-word'); otherwise, begin an incremental forward
     word search (`isearch-forward-word').

`M-s w <RET> WORDS <RET>'
     Search for WORDS, using a forward nonincremental word search.

`M-s w C-r <RET> WORDS <RET>'
     Search backward for WORDS, using a nonincremental word search.

   To begin a forward incremental word search, type `M-s w'.  If
incremental search is not already active, this runs the command
`isearch-forward-word'.  If incremental search is already active
(whether a forward or backward search), `M-s w' switches to a word
search while keeping the direction of the search and the current search
string unchanged.  You can toggle word search back off by typing `M-s
w' again.

   To begin a nonincremental word search, type `M-s w <RET>' for a
forward search, or `M-s w C-r <RET>' for a backward search.  These run
the commands `word-search-forward' and `word-search-backward'
respectively.

   Incremental and nonincremental word searches differ slightly in the
way they find a match.  In a nonincremental word search, the last word
in the search string must exactly match a whole word.  In an
incremental word search, the matching is more lax: the last word in the
search string can match part of a word, so that the matching proceeds
incrementally as you type.  This additional laxity does not apply to
the lazy highlight, which always matches whole words.


File: emacs,  Node: Regexp Search,  Next: Regexps,  Prev: Word Search,  Up: Search

19.4 Regular Expression Search
==============================

A "regular expression" (or "regexp" for short) is a pattern that
denotes a class of alternative strings to match.  GNU Emacs provides
both incremental and nonincremental ways to search for a match for a
regexp.  The syntax of regular expressions is explained in the
following section.

`C-M-s'
     Begin incremental regexp search (`isearch-forward-regexp').

`C-M-r'
     Begin reverse incremental regexp search
     (`isearch-backward-regexp').

   Incremental search for a regexp is done by typing `C-M-s'
(`isearch-forward-regexp'), by invoking `C-s' with a prefix argument
(whose value does not matter), or by typing `M-r' within a forward
incremental search.  This command reads a search string incrementally
just like `C-s', but it treats the search string as a regexp rather
than looking for an exact match against the text in the buffer.  Each
time you add text to the search string, you make the regexp longer, and
the new regexp is searched for.  To search backward for a regexp, use
`C-M-r' (`isearch-backward-regexp'), `C-r' with a prefix argument, or
`M-r' within a backward incremental search.

   All of the special key sequences in an ordinary incremental search
do similar things in an incremental regexp search.  For instance,
typing `C-s' immediately after starting the search retrieves the last
incremental search regexp used and searches forward for it.
Incremental regexp and non-regexp searches have independent defaults.
They also have separate search rings, which you can access with `M-p'
and `M-n'.

   If you type <SPC> in incremental regexp search, it matches any
sequence of whitespace characters, including newlines.  If you want to
match just a space, type `C-q <SPC>'.  You can control what a bare
space matches by setting the variable `search-whitespace-regexp' to the
desired regexp.

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

   Forward and backward regexp search are not symmetrical, because
regexp matching in Emacs always operates forward, starting with the
beginning of the regexp.  Thus, forward regexp search scans forward,
trying a forward match at each possible starting position.  Backward
regexp search scans backward, trying a forward match at each possible
starting position.  These search methods are not mirror images.

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

   If you use the incremental regexp search commands with a prefix
argument, they perform ordinary string search, like `isearch-forward'
and `isearch-backward'.  *Note Incremental Search::.


File: emacs,  Node: Regexps,  Next: Regexp Backslash,  Prev: Regexp Search,  Up: Search

19.5 Syntax of Regular Expressions
==================================

This manual describes regular expression features that users typically
use.  *Note Regular Expressions: (elisp)Regular Expressions, for
additional features used mainly in Lisp programs.

   Regular expressions have a syntax in which a few characters are
special constructs and the rest are "ordinary".  An ordinary character
matches that same character and nothing else.  The special characters
are `$^.*+?[\'.  The character `]' is special if it ends a character
alternative (see later).  The character `-' is special inside a
character alternative.  Any other character appearing in a regular
expression is ordinary, unless a `\' precedes it.  (When you use
regular expressions in a Lisp program, each `\' must be doubled, see
the example near the end of this section.)

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

   Any two regular expressions A and B can be concatenated.  The result
is a regular expression which matches a string if A matches some amount
of the beginning of that string and B matches the rest of the string.
For example, concatenating the regular expressions `f' and `o' gives
the regular expression `fo', which matches only the string `fo'.  Still
trivial.  To do something nontrivial, you need to use one of the special
characters.  Here is a list of them.

`.' (Period)
     is a special character that matches any single character except a
     newline.  For example, the regular expressions `a.b' matches any
     three-character string that begins with `a' and ends with `b'.

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

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

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

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

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

`*?', `+?', `??'
     are non-"greedy" variants of the operators above.  The normal
     operators `*', `+', `?' match as much as they can, as long as the
     overall regexp can still match.  With a following `?', they will
     match as little as possible.

     Thus, both `ab*' and `ab*?' can match the string `a' and the
     string `abbbb'; but if you try to match them both against the text
     `abbb', `ab*' will match it all (the longest valid match), while
     `ab*?'  will match just `a' (the shortest valid match).

     Non-greedy operators match the shortest possible string starting
     at a given starting point; in a forward search, though, the
     earliest possible starting point for match is always the one
     chosen.  Thus, if you search for `a.*?$' against the text `abbab'
     followed by a newline, it matches the whole string.  Since it
     _can_ match starting at the first `a', it does.

`\{N\}'
     is a postfix operator specifying N repetitions--that is, the
     preceding regular expression must match exactly N times in a row.
     For example, `x\{4\}' matches the string `xxxx' and nothing else.

`\{N,M\}'
     is a postfix operator specifying between N and M repetitions--that
     is, the preceding regular expression must match at least N times,
     but no more than M times.  If M is omitted, then there is no upper
     limit, but the preceding regular expression must match at least N
     times.
     `\{0,1\}' is equivalent to `?'.
     `\{0,\}' is equivalent to `*'.
     `\{1,\}' is equivalent to `+'.

`[ ... ]'
     is a "character set", beginning with `[' and terminated by `]'.

     In the simplest case, the characters between the two brackets are
     what this set can match.  Thus, `[ad]' matches either one `a' or
     one `d', and `[ad]*' matches any string composed of just `a's and
     `d's (including the empty string).  It follows that `c[ad]*r'
     matches `cr', `car', `cdr', `caddaar', etc.

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

     You can also include certain special "character classes" in a
     character set.  A `[:' and balancing `:]' enclose a character
     class inside a character alternative.  For instance, `[[:alnum:]]'
     matches any letter or digit.  *Note Char Classes: (elisp)Char
     Classes, for a list of character classes.

     To include a `]' in a character set, you must make it the first
     character.  For example, `[]a]' matches `]' or `a'.  To include a
     `-', write `-' as the first or last character of the set, or put
     it after a range.  Thus, `[]-]' matches both `]' and `-'.

     To include `^' in a set, put it anywhere but at the beginning of
     the set.  (At the beginning, it complements the set--see below.)

     When you use a range in case-insensitive search, you should write
     both ends of the range in upper case, or both in lower case, or
     both should be non-letters.  The behavior of a mixed-case range
     such as `A-z' is somewhat ill-defined, and it may change in future
     Emacs versions.

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

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

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

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

     For historical compatibility reasons, `^' can be used with this
     meaning only at the beginning of the regular expression, or after
     `\(' or `\|'.

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

     For historical compatibility reasons, `$' can be used with this
     meaning only at the end of the regular expression, or before `\)'
     or `\|'.

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

     Because `\' quotes special characters, `\$' is a regular
     expression that matches only `$', and `\[' is a regular expression
     that matches only `[', and so on.

     See the following section for the special constructs that begin
     with `\'.

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

   As a `\' is not special inside a character alternative, it can never
remove the special meaning of `-' or `]'.  So you should not quote
these characters when they have no special meaning either.  This would
not clarify anything, since backslashes can legitimately precede these
characters where they _have_ special meaning, as in `[^\]' (`"[^\\]"'
for Lisp string syntax), which matches any single character except a
backslash.


File: emacs,  Node: Regexp Backslash,  Next: Regexp Example,  Prev: Regexps,  Up: Search

19.6 Backslash in Regular Expressions
=====================================

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

`\|'
     specifies an alternative.  Two regular expressions A and B with
     `\|' in between form an expression that matches some text if
     either A matches it or B matches it.  It works by trying to match
     A, and if that fails, by trying to match B.

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

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

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

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

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

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

       3. To record a matched substring for future reference.

     This last application is not a consequence of the idea of a
     parenthetical grouping; it is a separate feature that is assigned
     as a second meaning to the same `\( ... \)' construct.  In practice
     there is usually no conflict between the two meanings; when there
     is a conflict, you can use a "shy" group.

`\(?: ... \)'
     specifies a "shy" group that does not record the matched substring;
     you can't refer back to it with `\D'.  This is useful in
     mechanically combining regular expressions, so that you can add
     groups for syntactic purposes without interfering with the
     numbering of the groups that are meant to be referred to.

`\D'
     matches the same text that matched the Dth occurrence of a `\( ...
     \)' construct.  This is called a "back reference".

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

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

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

     If a particular `\( ... \)' construct matches more than once
     (which can easily happen if it is followed by `*'), only the last
     match is recorded.

`\`'
     matches the empty string, but only at the beginning of the string
     or buffer (or its accessible portion) being matched against.

`\''
     matches the empty string, but only at the end of the string or
     buffer (or its accessible portion) being matched against.

`\='
     matches the empty string, but only at point.

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

     `\b' matches at the beginning or end of the buffer regardless of
     what text appears next to it.

`\B'
     matches the empty string, but _not_ at the beginning or end of a
     word.

`\<'
     matches the empty string, but only at the beginning of a word.
     `\<' matches at the beginning of the buffer only if a
     word-constituent character follows.

`\>'
     matches the empty string, but only at the end of a word.  `\>'
     matches at the end of the buffer only if the contents end with a
     word-constituent character.

`\w'
     matches any word-constituent character.  The syntax table
     determines which characters these are.  *Note Syntax::.

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

`\_<'
     matches the empty string, but only at the beginning of a symbol.
     A symbol is a sequence of one or more symbol-constituent
     characters.  A symbol-constituent character is a character whose
     syntax is either `w' or `_'.  `\_<' matches at the beginning of the
     buffer only if a symbol-constituent character follows.

`\_>'
     matches the empty string, but only at the end of a symbol.  `\_>'
     matches at the end of the buffer only if the contents end with a
     symbol-constituent character.

`\sC'
     matches any character whose syntax is C.  Here C is a character
     that designates a particular syntax class: thus, `w' for word
     constituent, `-' or ` ' for whitespace, `.' for ordinary
     punctuation, etc.  *Note Syntax::.

`\SC'
     matches any character whose syntax is not C.

`\cC'
     matches any character that belongs to the category C.  For
     example, `\cc' matches Chinese characters, `\cg' matches Greek
     characters, etc.  For the description of the known categories,
     type `M-x describe-categories <RET>'.

`\CC'
     matches any character that does _not_ belong to category C.

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


File: emacs,  Node: Regexp Example,  Next: Search Case,  Prev: Regexp Backslash,  Up: Search

19.7 Regular Expression Example
===============================

Here is an example of a regexp--the regexp that Emacs uses, by default,
to recognize the end of a sentence, not including the following space
(i.e., the variable `sentence-end-base'):

     [.?!][]\"'””)}]*

This contains two parts in succession: a character set matching period,
`?', or `!', and a character set matching close-brackets, quotes, or
parentheses, repeated zero or more times.


File: emacs,  Node: Search Case,  Next: Replace,  Prev: Regexp Example,  Up: Search

19.8 Searching and Case
=======================

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

   An upper-case letter anywhere in the incremental search string makes
the search case-sensitive.  Thus, searching for `Foo' does not find
`foo' or `FOO'.  This applies to regular expression search as well as
to string search.  The effect ceases if you delete the upper-case
letter from the search string.

   Typing `M-c' within an incremental search toggles the case
sensitivity of that search.  The effect does not extend beyond the
current incremental search to the next one, but it does override the
effect of adding or removing an upper-case letter in the current search.

   If you set the variable `case-fold-search' to `nil', then all
letters must match exactly, including case.  This is a per-buffer
variable; altering the variable normally affects only the current
buffer, unless you change its default value.  *Note Locals::.  This
variable applies to nonincremental searches also, including those
performed by the replace commands (*note Replace::) and the minibuffer
history matching commands (*note Minibuffer History::).

   Several related variables control case-sensitivity of searching and
matching for specific commands or activities.  For instance,
`tags-case-fold-search' controls case sensitivity for `find-tag'.  To
find these variables, do `M-x apropos-variable <RET> case-fold-search
<RET>'.


File: emacs,  Node: Replace,  Next: Other Repeating Search,  Prev: Search Case,  Up: Search

19.9 Replacement Commands
=========================

Emacs provides several commands for performing search-and-replace
operations.  In addition to the simple `M-x replace-string' command,
there is `M-%' (`query-replace'), which presents each occurrence of the
pattern and asks you whether to replace it.

   The replace commands normally operate on the text from point to the
end of the buffer.  When the mark is active, they operate on the region
instead (*note Mark::).  The basic replace commands replace one "search
string" (or regexp) with one "replacement string".  It is possible to
perform several replacements in parallel, using the command
`expand-region-abbrevs' (*note Expanding Abbrevs::).

* Menu:

* Unconditional Replace::   Replacing all matches for a string.
* Regexp Replace::          Replacing all matches for a regexp.
* Replacement and Case::    How replacements preserve case of letters.
* Query Replace::           How to use querying.


File: emacs,  Node: Unconditional Replace,  Next: Regexp Replace,  Prev: Replace,  Up: Replace

19.9.1 Unconditional Replacement
--------------------------------

`M-x replace-string <RET> STRING <RET> NEWSTRING <RET>'
     Replace every occurrence of STRING with NEWSTRING.

   To replace every instance of `foo' after point with `bar', use the
command `M-x replace-string' with the two arguments `foo' and `bar'.
Replacement happens only in the text after point, so if you want to
cover the whole buffer you must go to the beginning first.  All
occurrences up to the end of the buffer are replaced; to limit
replacement to part of the buffer, activate the region around that
part.  When the region is active, replacement is limited to the region
(*note Mark::).

   When `replace-string' exits, it leaves point at the last occurrence
replaced.  It adds the prior position of point (where the
`replace-string' command was issued) to the mark ring, without
activating the mark; use `C-u C-<SPC>' to move back there.  *Note Mark
Ring::.

   A prefix argument restricts replacement to matches that are
surrounded by word boundaries.  The argument's value doesn't matter.

   *Note Replacement and Case::, for details about case-sensitivity in
replace commands.


File: emacs,  Node: Regexp Replace,  Next: Replacement and Case,  Prev: Unconditional Replace,  Up: Replace

19.9.2 Regexp Replacement
-------------------------

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

`M-x replace-regexp <RET> REGEXP <RET> NEWSTRING <RET>'
     Replace every match for REGEXP with NEWSTRING.

   In `replace-regexp', the NEWSTRING need not be constant: it can
refer to all or part of what is matched by the REGEXP.  `\&' in
NEWSTRING stands for the entire match being replaced.  `\D' in
NEWSTRING, where D is a digit, stands for whatever matched the Dth
parenthesized grouping in REGEXP.  (This is called a "back reference.")
`\#' refers to the count of replacements already made in this command,
as a decimal number.  In the first replacement, `\#' stands for `0'; in
the second, for `1'; and so on.  For example,

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

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

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

performs the inverse transformation.  To include a `\' in the text to
replace with, you must enter `\\'.

   If you want to enter part of the replacement string by hand each
time, use `\?' in the replacement string.  Each replacement will ask
you to edit the replacement string in the minibuffer, putting point
where the `\?' was.

   The remainder of this subsection is intended for specialized tasks
and requires knowledge of Lisp.  Most readers can skip it.

   You can use Lisp expressions to calculate parts of the replacement
string.  To do this, write `\,' followed by the expression in the
replacement string.  Each replacement calculates the value of the
expression and converts it to text without quoting (if it's a string,
this means using the string's contents), and uses it in the replacement
string in place of the expression itself.  If the expression is a
symbol, one space in the replacement string after the symbol name goes
with the symbol name, so the value replaces them both.

   Inside such an expression, you can use some special sequences.  `\&'
and `\N' refer here, as usual, to the entire match as a string, and to
a submatch as a string.  N may be multiple digits, and the value of
`\N' is `nil' if subexpression N did not match.  You can also use `\#&'
and `\#N' to refer to those matches as numbers (this is valid when the
match or submatch has the form of a numeral).  `\#' here too stands for
the number of already-completed replacements.

   Repeating our example to exchange `x' and `y', we can thus do it
also this way:

     M-x replace-regexp <RET> \(x\)\|y <RET>
     \,(if \1 "y" "x") <RET>

   For computing replacement strings for `\,', the `format' function is
often useful (*note Formatting Strings: (elisp)Formatting Strings.).
For example, to add consecutively numbered strings like `ABC00042' to
columns 73 to 80 (unless they are already occupied), you can use

     M-x replace-regexp <RET> ^.\{0,72\}$ <RET>
     \,(format "%-72sABC%05d" \& \#) <RET>


File: emacs,  Node: Replacement and Case,  Next: Query Replace,  Prev: Regexp Replace,  Up: Replace

19.9.3 Replace Commands and Case
--------------------------------

If the first argument of a replace command is all lower case, the
command ignores case while searching for occurrences to
replace--provided `case-fold-search' is non-`nil'.  If
`case-fold-search' is set to `nil', case is always significant in all
searches.

   In addition, when the NEWSTRING argument is all or partly lower
case, replacement commands try to preserve the case pattern of each
occurrence.  Thus, the command

     M-x replace-string <RET> foo <RET> bar <RET>

replaces a lower case `foo' with a lower case `bar', an all-caps `FOO'
with `BAR', and a capitalized `Foo' with `Bar'.  (These three
alternatives--lower case, all caps, and capitalized, are the only ones
that `replace-string' can distinguish.)

   If upper-case letters are used in the replacement string, they remain
upper case every time that text is inserted.  If upper-case letters are
used in the first argument, the second argument is always substituted
exactly as given, with no case conversion.  Likewise, if either
`case-replace' or `case-fold-search' is set to `nil', replacement is
done without case conversion.


File: emacs,  Node: Query Replace,  Prev: Replacement and Case,  Up: Replace

19.9.4 Query Replace
--------------------

`M-% STRING <RET> NEWSTRING <RET>'
`M-x query-replace <RET> STRING <RET> NEWSTRING <RET>'
     Replace some occurrences of STRING with NEWSTRING.

`C-M-% REGEXP <RET> NEWSTRING <RET>'
`M-x query-replace-regexp <RET> REGEXP <RET> NEWSTRING <RET>'
     Replace some matches for REGEXP with NEWSTRING.

   If you want to change only some of the occurrences of `foo' to
`bar', not all of them, use `M-%' (`query-replace').  This command
finds occurrences of `foo' one by one, displays each occurrence and
asks you whether to replace it.  Aside from querying, `query-replace'
works just like `replace-string' (*note Unconditional Replace::).  In
particular, it preserves case provided `case-replace' is non-`nil', as
it normally is (*note Replacement and Case::).  A numeric argument
means consider only occurrences that are bounded by word-delimiter
characters.

   `C-M-%' performs regexp search and replace (`query-replace-regexp').
It works like `replace-regexp' except that it queries like
`query-replace'.

   These commands highlight the current match using the face
`query-replace'.  They highlight other matches using `lazy-highlight'
just like incremental search (*note Incremental Search::).  By default,
`query-replace-regexp' will show substituted replacement string for the
current match in the minibuffer.  If you want to keep special sequences
`\&' and `\N' unexpanded, customize `query-replace-show-replacement'
variable.

   The characters you can type when you are shown a match for the string
or regexp are:

`<SPC>'
     to replace the occurrence with NEWSTRING.

`<DEL>'
     to skip to the next occurrence without replacing this one.

`, (Comma)'
     to replace this occurrence and display the result.  You are then
     asked for another input character to say what to do next.  Since
     the replacement has already been made, <DEL> and <SPC> are
     equivalent in this situation; both move to the next occurrence.

     You can type `C-r' at this point (see below) to alter the replaced
     text.  You can also type `C-x u' to undo the replacement; this
     exits the `query-replace', so if you want to do further
     replacement you must use `C-x <ESC> <ESC> <RET>' to restart (*note
     Repetition::).

`<RET>'
     to exit without doing any more replacements.

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

`!'
     to replace all remaining occurrences without asking again.

`^'
     to go back to the position of the previous occurrence (or what
     used to be an occurrence), in case you changed it by mistake or
     want to reexamine it.

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

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

`e'
     to edit the replacement string in the minibuffer.  When you exit
     the minibuffer by typing <RET>, the minibuffer contents replace the
     current occurrence of the pattern.  They also become the new
     replacement string for any further occurrences.

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

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

   Some other characters are aliases for the ones listed above: `y',
`n' and `q' are equivalent to <SPC>, <DEL> and <RET>.

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

   To restart a `query-replace' once it is exited, use `C-x <ESC>
<ESC>', which repeats the `query-replace' because it used the
minibuffer to read its arguments.  *Note C-x ESC ESC: Repetition.

   *Note Operating on Files::, for the Dired `Q' command which performs
query replace on selected files.  See also *note Transforming File
Names::, for Dired commands to rename, copy, or link files by replacing
regexp matches in file names.


File: emacs,  Node: Other Repeating Search,  Prev: Replace,  Up: Search

19.10 Other Search-and-Loop Commands
====================================

Here are some other commands that find matches for a regular
expression.  They all ignore case in matching, if the pattern contains
no upper-case letters and `case-fold-search' is non-`nil'.  Aside from
`occur' and its variants, all operate on the text from point to the end
of the buffer, or on the region if it is active.

`M-x multi-isearch-buffers'
     Prompt for one or more buffer names, ending with <RET>; then,
     begin a multi-buffer incremental search in those buffers.  (If the
     search fails in one buffer, the next `C-s' tries searching the
     next specified buffer, and so forth.)  With a prefix argument,
     prompt for a regexp and begin a multi-buffer incremental search in
     buffers matching that regexp.

`M-x multi-isearch-buffers-regexp'
     This command is just like `multi-isearch-buffers', except it
     performs an incremental regexp search.

`M-x occur'
     Prompt for a regexp, and display a list showing each line in the
     buffer that contains a match for it.  To limit the search to part
     of the buffer, narrow to that part (*note Narrowing::).  A numeric
     argument N specifies that N lines of context are to be displayed
     before and after each matching line.  Currently, `occur' can not
     correctly handle multiline matches.

     The buffer `*Occur*' containing the output serves as a menu for
     finding the occurrences in their original context.  Click
     `Mouse-2' on an occurrence listed in `*Occur*', or position point
     there and type <RET>; this switches to the buffer that was
     searched and moves point to the original of the chosen occurrence.
     `o' and `C-o' display the match in another window; `C-o' does not
     select it.

     After using `M-x occur', you can use `next-error' to visit the
     occurrences found, one by one.  *note Compilation Mode::.

`M-s o'
     Run `occur' using the search string of the last incremental string
     search.  You can also run `M-s o' when an incremental search is
     active; this uses the current search string.

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

`M-x multi-occur'
     This command is just like `occur', except it is able to search
     through multiple buffers.  It asks you to specify the buffer names
     one by one.

`M-x multi-occur-in-matching-buffers'
     This command is similar to `multi-occur', except the buffers to
     search are specified by a regular expression that matches visited
     file names.  With a prefix argument, it uses the regular
     expression to match buffer names instead.

`M-x how-many'
     Prompt for a regexp, and print the number of matches for it in the
     buffer after point.  If the region is active, this operates on the
     region instead.

`M-x flush-lines'
     Prompt for a regexp, and delete each line that contains a match for
     it, operating on the text after point.  This command deletes the
     current line if it contains a match starting after point.  If the
     region is active, it operates on the region instead; if a line
     partially contained in the region contains a match entirely
     contained in the region, it is deleted.

     If a match is split across lines, `flush-lines' deletes all those
     lines.  It deletes the lines before starting to look for the next
     match; hence, it ignores a match starting on the same line at which
     another match ended.

`M-x keep-lines'
     Prompt for a regexp, and delete each line that _does not_ contain
     a match for it, operating on the text after point.  If point is
     not at the beginning of a line, this command always keeps the
     current line.  If the region is active, the command operates on
     the region instead; it never deletes lines that are only partially
     contained in the region (a newline that ends a line counts as part
     of that line).

     If a match is split across lines, this command keeps all those
     lines.


File: emacs,  Node: Fixit,  Next: Keyboard Macros,  Prev: Search,  Up: Top

20 Commands for Fixing Typos
****************************

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

   The most fundamental command for correcting erroneous editing is the
undo command `C-/' (which is also bound to `C-x u' and `C-_').  This
undoes a single command, or a part of a command (as in the case of
`query-replace'), or several consecutive self-inserting characters.
Consecutive repetitions of `C-/' undo earlier and earlier changes, back
to the limit of the undo information available.

   Aside from the commands described here, you can erase text using
deletion commands such as <DEL> (`delete-backward-char').  These were
described earlier in this manual.  *Note Erasing::.

* Menu:

* Undo::        The Undo commands.
* Transpose::   Exchanging two characters, words, lines, lists...
* Fixing Case:: Correcting case of last word entered.
* Spelling::    Apply spelling checker to a word, or a whole file.


File: emacs,  Node: Undo,  Next: Transpose,  Up: Fixit

20.1 Undo
=========

The "undo" command reverses recent changes in the buffer's text.  Each
buffer records changes individually, and the undo command always
applies to the current buffer.  You can undo all the changes in a
buffer for as far as back its records go.  Usually, each editing
command makes a separate entry in the undo records, but some commands
such as `query-replace' divide their changes into multiple entries for
flexibility in undoing.  Consecutive character insertion commands are
usually grouped together into a single undo record, to make undoing
less tedious.

`C-/'
`C-x u'
`C-_'
     Undo one entry in the current buffer's undo records (`undo').

   To begin to undo, type `C-/' (or its aliases, `C-_' or `C-x u')(1).
This undoes the most recent change in the buffer, and moves point back
to where it was before that change.

   Consecutive repetitions of `C-/' (or its aliases) undo earlier and
earlier changes in the current buffer.  If all the recorded changes
have already been undone, the undo command signals an error.

   Any command other than an undo command breaks the sequence of undo
commands.  Starting from that moment, the entire sequence of undo
commands that you have just performed are themselves placed into the
undo record, as a single set of changes.  Therefore, to re-apply
changes you have undone, type `C-f' or any other command that
harmlessly breaks the sequence of undoing; then type `C-/' to undo the
undo command.

   On the other hand, if you want to resume undoing, without redoing
previous undo commands, use `M-x undo-only'.  This is like `undo', but
will not redo changes you have just undone.

   If you notice that a buffer has been modified accidentally, the
easiest way to recover is to type `C-/' repeatedly until the stars
disappear from the front of the mode line (*note Mode Line::).
Whenever an undo command makes the stars disappear from the mode line,
it means that the buffer contents are the same as they were when the
file was last read in or saved.  If you do not remember whether you
changed the buffer deliberately, type `C-/' once.  When you see the
last change you made undone, you will see whether it was an intentional
change.  If it was an accident, leave it undone.  If it was deliberate,
redo the change as described above.

   When there is an active region, any use of `undo' performs
"selective undo": it undoes the most recent change within the region,
instead of the entire buffer.  However, when Transient Mark mode is off
(*note Persistent Mark::), `C-/' always operates on the entire buffer,
ignoring the region.  In this case, you can perform selective undo by
supplying a prefix argument to the `undo' command: `C-u C-/'.  To undo
further changes in the same region, repeat the `undo' command (no
prefix argument is needed).

   Some specialized buffers do not make undo records.  Buffers whose
names start with spaces never do; these buffers are used internally by
Emacs to hold text that users don't normally look at or edit.

   When the undo records for a buffer becomes too large, Emacs discards
the oldest undo records from time to time (during "garbage
collection").  You can specify how much undo records to keep by setting
the variables `undo-limit', `undo-strong-limit', and
`undo-outer-limit'.  Their values are expressed in bytes.

   The variable `undo-limit' sets a soft limit: Emacs keeps undo data
for enough commands to reach this size, and perhaps exceed it, but does
not keep data for any earlier commands beyond that.  Its default value
is 80000.  The variable `undo-strong-limit' sets a stricter limit: any
previous command (though not the most recent one) that pushes the size
past this amount is forgotten.  The default value of
`undo-strong-limit' is 120000.

   Regardless of the values of those variables, the most recent change
is never discarded unless it gets bigger than `undo-outer-limit'
(normally 12,000,000).  At that point, Emacs discards the undo data and
warns you about it.  This is the only situation in which you cannot
undo the last command.  If this happens, you can increase the value of
`undo-outer-limit' to make it even less likely to happen in the future.
But if you didn't expect the command to create such large undo data,
then it is probably a bug and you should report it.  *Note Reporting
Bugs: Bugs.

   ---------- Footnotes ----------

   (1) Aside from `C-/', the `undo' command is also bound to `C-x u'
because that is more straightforward for beginners to remember: `u'
stands for "undo".  It is also bound to `C-_' because typing `C-/' on
some text-only terminals actually enters `C-_'.


File: emacs,  Node: Transpose,  Next: Fixing Case,  Prev: Undo,  Up: Fixit

20.2 Transposing Text
=====================

`C-t'
     Transpose two characters (`transpose-chars').

`M-t'
     Transpose two words (`transpose-words').

`C-M-t'
     Transpose two balanced expressions (`transpose-sexps').

`C-x C-t'
     Transpose two lines (`transpose-lines').

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

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

   `C-M-t' (`transpose-sexps') is a similar command for transposing two
expressions (*note Expressions::), and `C-x C-t' (`transpose-lines')
exchanges lines.  They work like `M-t' except as regards what units of
text they transpose.

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

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


File: emacs,  Node: Fixing Case,  Next: Spelling,  Prev: Transpose,  Up: Fixit

20.3 Case Conversion
====================

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

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

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

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


File: emacs,  Node: Spelling,  Prev: Fixing Case,  Up: Fixit

20.4 Checking and Correcting Spelling
=====================================

This section describes the commands to check the spelling of a single
word or of a portion of a buffer.  These commands only work if the
spelling checker program Aspell, Ispell or Hunspell is installed.
Aspell, Ispell or Hunspell are not part of Emacs, but one or the other
is usually installed in GNU/Linux and other free operating systems.
*Note Aspell: (aspell)Top.

`M-$'
     Check and correct spelling of the active region or the word at
     point (`ispell-word').

`M-x ispell'
     Check and correct spelling in the active region or the entire
     buffer.

`M-x ispell-buffer'
     Check and correct spelling in the buffer.

`M-x ispell-region'
     Check and correct spelling in the region.

`M-x ispell-message'
     Check and correct spelling in a draft mail message, excluding cited
     material.

`M-x ispell-change-dictionary <RET> DICT <RET>'
     Restart the Aspell/Ispell/Hunspell process, using DICT as the
     dictionary.

`M-x ispell-kill-ispell'
     Kill the Aspell/Ispell/Hunspell subprocess.

`M-<TAB>'
`<ESC> <TAB>'
     Complete the word before point based on the spelling dictionary
     (`ispell-complete-word').

`M-x flyspell-mode'
     Enable Flyspell mode, which highlights all misspelled words.

`M-x flyspell-prog-mode'
     Enable Flyspell mode for comments and strings only.

   To check the spelling of the word around or before point, and
optionally correct it as well, type `M-$' (`ispell-word').  If a region
is active, `M-$' checks the spelling of all words within the region.
*Note Mark::.  (When Transient Mark mode is off, `M-$' always acts on
the word around or before point, ignoring the region.  *Note Persistent
Mark::.)

   Similarly, the command `M-x ispell' performs spell-checking in the
region if one is active, or in the entire buffer otherwise.  The
commands `M-x ispell-buffer' and `M-x ispell-region' explicitly perform
spell-checking on the entire buffer or the region respectively.  To
check spelling in an email message you are writing, use `M-x
ispell-message'; that command checks the whole buffer, except for
material that is indented or appears to be cited from other messages.
*Note Sending Mail::.

   When one of these commands encounters what appears to be an
incorrect word, it asks you what to do.  It usually displays a list of
numbered "near-misses"--words that are close to the incorrect word.
Then you must type a single-character response.  Here are the valid
responses:

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

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

`r NEW <RET>'
     Replace the word, just this time, with NEW.  (The replacement
     string will be rescanned for more spelling errors.)

`R NEW <RET>'
     Replace the word with NEW, and do a `query-replace' so you can
     replace it elsewhere in the buffer if you wish.  (The replacements
     will be rescanned for more spelling errors.)

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

`A'
     Accept the incorrect word--treat it as correct, but only in this
     editing session and for this buffer.

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

`m'
     Like `i', but you can also specify dictionary completion
     information.

`u'
     Insert the lower-case version of this word in your private
     dictionary file.

`l WORD <RET>'
     Look in the dictionary for words that match WORD.  These words
     become the new list of "near-misses"; you can select one of them as
     the replacement by typing a digit.  You can use `*' in WORD as a
     wildcard.

`C-g'
`X'
     Quit interactive spell checking, leaving point at the word that was
     being checked.  You can restart checking again afterward with `C-u
     M-$'.

`x'
     Quit interactive spell checking and move point back to where it was
     when you started spell checking.

`q'
     Quit interactive spell checking and kill the spell-checker
     subprocess.

`?'
     Show the list of options.

   In Text mode and related modes, the command `M-<TAB>'
(`ispell-complete-word') shows a list of completions based on spelling
correction.  Insert the beginning of a word, and then type `M-<TAB>';
the command displays a completion list window.  (If your window manager
intercepts `M-<TAB>', type `<ESC> <TAB>' or `C-M-i'.)  To choose one of
the completions listed, click `Mouse-2' or `Mouse-1' fast on it, or
move the cursor there in the completions window and type <RET>.  *Note
Text Mode::.

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

   Ispell, Aspell and Hunspell use two dictionaries together for spell
checking: the standard dictionary and your private dictionary.  The
standard dictionary is specified by `ispell-local-dictionary' or, if
`nil', by `ispell-dictionary'.  If both are `nil' the default
dictionary is selected.  The command `M-x ispell-change-dictionary'
sets the standard dictionary for the buffer and then restarts the
subprocess, so that it will use a different standard dictionary.
Personal dictionary is specified by `ispell-personal-dictionary'.  If
`nil', default value is used.

   Set variable `ispell-dictionary' to select a specific default
dictionary for all your documents. Set variable
`ispell-local-dictionary' in the local variables section to select a
specific dictionary for a given document.

   A separate dictionary is used for word completion.  The variable
`ispell-complete-word-dict' specifies the file name of this dictionary.
The completion dictionary must be different because it cannot use root
and affix information.  For some languages, there is a spell checking
dictionary but no word completion dictionary.

   Flyspell mode is a fully-automatic way to check spelling as you edit
in Emacs.  It operates by checking words as you change or insert them.
When it finds a word that it does not recognize, it highlights that
word.  This does not interfere with your editing, but when you see the
highlighted word, you can move to it and fix it.  Type `M-x
flyspell-mode' to enable or disable this mode in the current buffer.  To
enable `flyspell-mode' in all text mode buffers, add `turn-on-flyspell'
to `text-mode-hook'.

   When Flyspell mode highlights a word as misspelled, you can click on
it with `Mouse-2' to display a menu of possible corrections and
actions.  You can also correct the word by editing it manually in any
way you like.

   Flyspell Prog mode works just like ordinary Flyspell mode, except
that it only checks words in comments and string constants.  This
feature is useful for editing programs.  Type `M-x flyspell-prog-mode'
to enable or disable this mode in the current buffer.


File: emacs,  Node: Keyboard Macros,  Next: Files,  Prev: Fixit,  Up: Top

21 Keyboard Macros
******************

In this chapter we describe how to record a sequence of editing
commands so you can repeat it conveniently later.

   A "keyboard macro" is a command defined by an Emacs user to stand for
another sequence of keys.  For example, if you discover that you are
about to type `C-n M-d C-d' forty times, you can speed your work by
defining a keyboard macro to do `C-n M-d C-d', and then executing it 39
more times.

   You define a keyboard macro by executing and recording the commands
which are its definition.  Put differently, as you define a keyboard
macro, the definition is being executed for the first time.  This way,
you can see the effects of your commands, so that you don't have to
figure them out in your head.  When you close the definition, the
keyboard macro is defined and also has been, in effect, executed once.
You can then do the whole thing over again by invoking the macro.

   Keyboard macros differ from ordinary Emacs commands in that they are
written in the Emacs command language rather than in Lisp.  This makes
it easier for the novice to write them, and makes them more convenient
as temporary hacks.  However, the Emacs command language is not powerful
enough as a programming language to be useful for writing anything
intelligent or general.  For such things, Lisp must be used.

* Menu:

* Basic Keyboard Macro::     Defining and running keyboard macros.
* Keyboard Macro Ring::      Where previous keyboard macros are saved.
* Keyboard Macro Counter::   Inserting incrementing numbers in macros.
* Keyboard Macro Query::     Making keyboard macros do different things each time.
* Save Keyboard Macro::      Giving keyboard macros names; saving them in files.
* Edit Keyboard Macro::      Editing keyboard macros.
* Keyboard Macro Step-Edit:: Interactively executing and editing a keyboard
                               macro.


File: emacs,  Node: Basic Keyboard Macro,  Next: Keyboard Macro Ring,  Up: Keyboard Macros

21.1 Basic Use
==============

`<F3>'
     Start defining a keyboard macro
     (`kmacro-start-macro-or-insert-counter').

`<F4>'
     If a keyboard macro is being defined, end the definition;
     otherwise, execute the most recent keyboard macro
     (`kmacro-end-or-call-macro').

`C-u <F3>'
     Re-execute last keyboard macro, then append keys to its definition.

`C-u C-u <F3>'
     Append keys to the last keyboard macro without re-executing it.

`C-x C-k r'
     Run the last keyboard macro on each line that begins in the region
     (`apply-macro-to-region-lines').

   To start defining a keyboard macro, type <F3>.  From then on, your
keys continue to be executed, but also become part of the definition of
the macro.  `Def' appears in the mode line to remind you of what is
going on.  When you are finished, type <F4>
(`kmacro-end-or-call-macro') to terminate the definition.  For example,

     <F3> M-f foo <F4>

defines a macro to move forward a word and then insert `foo'.  Note
that <F3> and <F4> do not become part of the macro.

   After defining the macro, you can call it with <F4>.  For the above
example, this has the same effect as typing `M-f foo' again.  (Note the
two roles of the <F4> command: it ends the macro if you are in the
process of defining one, or calls the last macro otherwise.)  You can
also supply <F4> with a numeric prefix argument `n', which means to
invoke the macro `n' times.  An argument of zero repeats the macro
indefinitely, until it gets an error or you type `C-g' (or, on MS-DOS,
`C-<BREAK>').

   The above example demonstrates a handy trick that you can employ
with keyboard macros: if you wish to repeat an operation at regularly
spaced places in the text, include a motion command as part of the
macro.  In this case, repeating the macro inserts the string `foo'
after each successive word.

   After terminating the definition of a keyboard macro, you can append
more keystrokes to its definition by typing `C-u <F3>'.  This is
equivalent to plain <F3> followed by retyping the whole definition so
far.  As a consequence, it re-executes the macro as previously defined.
If you change the variable `kmacro-execute-before-append' to `nil', the
existing macro will not be re-executed before appending to it (the
default is `t').  You can also add to the end of the definition of the
last keyboard macro without re-executing it by typing `C-u C-u <F3>'.

   When a command reads an argument with the minibuffer, your
minibuffer input becomes part of the macro along with the command.  So
when you replay the macro, the command gets the same argument as when
you entered the macro.  For example,

     <F3> C-a C-k C-x b foo <RET> C-y C-x b <RET> <F4>

defines a macro that kills the current line, yanks it into the buffer
`foo', then returns to the original buffer.

   Most keyboard commands work as usual in a keyboard macro definition,
with some exceptions.  Typing `C-g' (`keyboard-quit') quits the
keyboard macro definition.  Typing `C-M-c' (`exit-recursive-edit') can
be unreliable: it works as you'd expect if exiting a recursive edit
that started within the macro, but if it exits a recursive edit that
started before you invoked the keyboard macro, it also necessarily
exits the keyboard macro too.  Mouse events are also unreliable, even
though you can use them in a keyboard macro: when the macro replays the
mouse event, it uses the original mouse position of that event, the
position that the mouse had while you were defining the macro.  The
effect of this may be hard to predict.

   The command `C-x C-k r' (`apply-macro-to-region-lines') repeats the
last defined keyboard macro on each line that begins in the region.  It
does this line by line, by moving point to the beginning of the line
and then executing the macro.

   In addition to the <F3> and <F4> commands described above, Emacs
also supports an older set of keybindings for defining and executing
keyboard macros.  To begin a macro definition, type `C-x ('
(`kmacro-start-macro'); as with <F3>, a prefix argument appends this
definition to the last keyboard macro.  To end a macro definition, type
`C-x )' (`kmacro-end-macro').  To execute the most recent macro, type
`C-x e' (`kmacro-end-and-call-macro').  If you enter `C-x e' while
defining a macro, the macro is terminated and executed immediately.
Immediately after typing `C-x e', you can type <e> repeatedly to
immediately repeat the macro one or more times.  You can also give `C-x
e' a repeat argument, just like <F4>.

   `C-x )' can be given a repeat count as an argument.  This means to
repeat the macro right after defining it.  The macro definition itself
counts as the first repetition, since it is executed as you define it,
so `C-u 4 C-x )' executes the macro immediately 3 additional times.


File: emacs,  Node: Keyboard Macro Ring,  Next: Keyboard Macro Counter,  Prev: Basic Keyboard Macro,  Up: Keyboard Macros

21.2 The Keyboard Macro Ring
============================

All defined keyboard macros are recorded in the "keyboard macro ring".
There is only one keyboard macro ring, shared by all buffers.

`C-x C-k C-k'
     Execute the keyboard macro at the head of the ring
     (`kmacro-end-or-call-macro-repeat').

`C-x C-k C-n'
     Rotate the keyboard macro ring to the next macro (defined earlier)
     (`kmacro-cycle-ring-next').

`C-x C-k C-p'
     Rotate the keyboard macro ring to the previous macro (defined
     later) (`kmacro-cycle-ring-previous').

   All commands which operate on the keyboard macro ring use the same
`C-x C-k' prefix.  Most of these commands can be executed and repeated
immediately after each other without repeating the `C-x C-k' prefix.
For example,

     C-x C-k C-p C-p C-k C-k C-k C-n C-n C-k C-p C-k C-d

will rotate the keyboard macro ring to the "second previous" macro,
execute the resulting head macro three times, rotate back to the
original head macro, execute that once, rotate to the "previous" macro,
execute that, and finally delete it from the macro ring.

   The command `C-x C-k C-k' (`kmacro-end-or-call-macro-repeat')
executes the keyboard macro at the head of the macro ring.  You can
repeat the macro immediately by typing another `C-k', or you can rotate
the macro ring immediately by typing `C-n' or `C-p'.

   When a keyboard macro is being defined, `C-x C-k C-k' behaves like
<F4> except that, immediately afterward, you can use most key bindings
of this section without the `C-x C-k' prefix.  For instance, another
`C-k' will re-execute the macro.

   The commands `C-x C-k C-n' (`kmacro-cycle-ring-next') and `C-x C-k
C-p' (`kmacro-cycle-ring-previous') rotate the macro ring, bringing the
next or previous keyboard macro to the head of the macro ring.  The
definition of the new head macro is displayed in the echo area.  You
can continue to rotate the macro ring immediately by repeating just
`C-n' and `C-p' until the desired macro is at the head of the ring.  To
execute the new macro ring head immediately, just type `C-k'.

   Note that Emacs treats the head of the macro ring as the "last
defined keyboard macro."  For instance, <F4> will execute that macro,
and `C-x C-k n' will give it a name.

   The maximum number of macros stored in the keyboard macro ring is
determined by the customizable variable `kmacro-ring-max'.


File: emacs,  Node: Keyboard Macro Counter,  Next: Keyboard Macro Query,  Prev: Keyboard Macro Ring,  Up: Keyboard Macros

21.3 The Keyboard Macro Counter
===============================

Each keyboard macro has an associated counter, which is initialized to
0 when you start defining the macro.  This counter allows you to insert
a number into the buffer that depends on the number of times the macro
has been called.  The counter is incremented each time its value is
inserted into the buffer.

`<F3>'
     In a keyboard macro definition, insert the keyboard macro counter
     value in the buffer (`kmacro-start-macro-or-insert-counter').

`C-x C-k C-i'
     Insert the keyboard macro counter value in the buffer
     (`kmacro-insert-counter').

`C-x C-k C-c'
     Set the keyboard macro counter (`kmacro-set-counter').

`C-x C-k C-a'
     Add the prefix arg to the keyboard macro counter
     (`kmacro-add-counter').

`C-x C-k C-f'
     Specify the format for inserting the keyboard macro counter
     (`kmacro-set-format').

   When you are defining a keyboard macro, the command <F3>
(`kmacro-start-macro-or-insert-counter') inserts the current value of
the keyboard macro's counter into the buffer, and increments the
counter by 1.  (If you are not defining a macro, <F3> begins a macro
definition instead.  *Note Basic Keyboard Macro::.)  You can use a
numeric prefix argument to specify a different increment.  If you just
specify a `C-u' prefix, that is the same as an increment of zero: it
inserts the current counter value without changing it.

   As an example, let us show how the keyboard macro counter can be
used to build a numbered list.  Consider the following key sequence:

     <F3> C-a <F3> . <SPC> <F4>

As part of this keyboard macro definition, the string `0. ' was
inserted into the beginning of the current line.  If you now move
somewhere else in the buffer and type <F4> to invoke the macro, the
string `1. ' is inserted at the beginning of that line.  Subsequent
invocations insert `2. ', `3. ', and so forth.

   The command `C-x C-k C-i' (`kmacro-insert-counter') does the same
thing as <F3>, but it can be used outside a keyboard macro definition.
When no keyboard macro is being defined or executed, it inserts and
increments the counter of the macro at the head of the keyboard macro
ring.

   The command `C-x C-k C-c' (`kmacro-set-counter') sets the current
macro counter to the value of the numeric argument.  If you use it
inside the macro, it operates on each repetition of the macro.  If you
specify just `C-u' as the prefix, while executing the macro, that
resets the counter to the value it had at the beginning of the current
repetition of the macro (undoing any increments so far in this
repetition).

   The command `C-x C-k C-a' (`kmacro-add-counter') adds the prefix
argument to the current macro counter.  With just `C-u' as argument, it
resets the counter to the last value inserted by any keyboard macro.
(Normally, when you use this, the last insertion will be in the same
macro and it will be the same counter.)

   The command `C-x C-k C-f' (`kmacro-set-format') prompts for the
format to use when inserting the macro counter.  The default format is
`%d', which means to insert the number in decimal without any padding.
You can exit with empty minibuffer to reset the format to this default.
You can specify any format string that the `format' function accepts
and that makes sense with a single integer extra argument (*note
Formatting Strings: (elisp)Formatting Strings.).  Do not put the format
string inside double quotes when you insert it in the minibuffer.

   If you use this command while no keyboard macro is being defined or
executed, the new format affects all subsequent macro definitions.
Existing macros continue to use the format in effect when they were
defined.  If you set the format while defining a keyboard macro, this
affects the macro being defined from that point on, but it does not
affect subsequent macros.  Execution of the macro will, at each step,
use the format in effect at that step during its definition.  Changes
to the macro format during execution of a macro, like the corresponding
changes during its definition, have no effect on subsequent macros.

   The format set by `C-x C-k C-f' does not affect insertion of numbers
stored in registers.

   If you use a register as a counter, incrementing it on each
repetition of the macro, that accomplishes the same thing as a keyboard
macro counter.  *Note RegNumbers::.  For most purposes, it is simpler
to use a keyboard macro counter.


File: emacs,  Node: Keyboard Macro Query,  Next: Save Keyboard Macro,  Prev: Keyboard Macro Counter,  Up: Keyboard Macros

21.4 Executing Macros with Variations
=====================================

In a keyboard macro, you can create an effect similar to that of
`query-replace', in that the macro asks you each time around whether to
make a change.

`C-x q'
     When this point is reached during macro execution, ask for
     confirmation (`kbd-macro-query').

   While defining the macro, type `C-x q' at the point where you want
the query to occur.  During macro definition, the `C-x q' does nothing,
but when you run the macro later, `C-x q' asks you interactively
whether to continue.

   The valid responses when `C-x q' asks are:

<SPC> (or `y')
     Continue executing the keyboard macro.

<DEL> (or `n')
     Skip the remainder of this repetition of the macro, and start right
     away with the next repetition.

<RET> (or `q')
     Skip the remainder of this repetition and cancel further
     repetitions.

`C-r'
     Enter a recursive editing level, in which you can perform editing
     which is not part of the macro.  When you exit the recursive edit
     using `C-M-c', you are asked again how to continue with the
     keyboard macro.  If you type a <SPC> at this time, the rest of the
     macro definition is executed.  It is up to you to leave point and
     the text in a state such that the rest of the macro will do what
     you want.

   `C-u C-x q', which is `C-x q' with a numeric argument, performs a
completely different function.  It enters a recursive edit reading
input from the keyboard, both when you type it during the definition of
the macro, and when it is executed from the macro.  During definition,
the editing you do inside the recursive edit does not become part of
the macro.  During macro execution, the recursive edit gives you a
chance to do some particularized editing on each repetition.  *Note
Recursive Edit::.


File: emacs,  Node: Save Keyboard Macro,  Next: Edit Keyboard Macro,  Prev: Keyboard Macro Query,  Up: Keyboard Macros

21.5 Naming and Saving Keyboard Macros
======================================

`C-x C-k n'
     Give a command name (for the duration of the Emacs session) to the
     most recently defined keyboard macro (`kmacro-name-last-macro').

`C-x C-k b'
     Bind the most recently defined keyboard macro to a key sequence
     (for the duration of the session) (`kmacro-bind-to-key').

`M-x insert-kbd-macro'
     Insert in the buffer a keyboard macro's definition, as Lisp code.

   If you wish to save a keyboard macro for later use, you can give it
a name using `C-x C-k n' (`kmacro-name-last-macro').  This reads a name
as an argument using the minibuffer and defines that name to execute
the last keyboard macro, in its current form.  (If you later add to the
definition of this macro, that does not alter the name's definition as
a macro.)  The macro name is a Lisp symbol, and defining it in this way
makes it a valid command name for calling with `M-x' or for binding a
key to with `global-set-key' (*note Keymaps::).  If you specify a name
that has a prior definition other than a keyboard macro, an error
message is shown and nothing is changed.

   You can also bind the last keyboard macro (in its current form) to a
key, using `C-x C-k b' (`kmacro-bind-to-key') followed by the key
sequence you want to bind.  You can bind to any key sequence in the
global keymap, but since most key sequences already have other
bindings, you should select the key sequence carefully.  If you try to
bind to a key sequence with an existing binding (in any keymap), this
command asks you for confirmation before replacing the existing binding.

   To avoid problems caused by overriding existing bindings, the key
sequences `C-x C-k 0' through `C-x C-k 9' and `C-x C-k A' through `C-x
C-k Z' are reserved for your own keyboard macro bindings.  In fact, to
bind to one of these key sequences, you only need to type the digit or
letter rather than the whole key sequences.  For example,

     C-x C-k b 4

will bind the last keyboard macro to the key sequence `C-x C-k 4'.

   Once a macro has a command name, you can save its definition in a
file.  Then it can be used in another editing session.  First, visit
the file you want to save the definition in.  Then use this command:

     M-x insert-kbd-macro <RET> MACRONAME <RET>

This inserts some Lisp code that, when executed later, will define the
same macro with the same definition it has now.  (You need not
understand Lisp code to do this, because `insert-kbd-macro' writes the
Lisp code for you.)  Then save the file.  You can load the file later
with `load-file' (*note Lisp Libraries::).  If the file you save in is
your init file `~/.emacs' (*note Init File::) then the macro will be
defined each time you run Emacs.

   If you give `insert-kbd-macro' a numeric argument, it makes
additional Lisp code to record the keys (if any) that you have bound to
MACRONAME, so that the macro will be reassigned the same keys when you
load the file.


File: emacs,  Node: Edit Keyboard Macro,  Next: Keyboard Macro Step-Edit,  Prev: Save Keyboard Macro,  Up: Keyboard Macros

21.6 Editing a Keyboard Macro
=============================

`C-x C-k C-e'
     Edit the last defined keyboard macro (`kmacro-edit-macro').

`C-x C-k e NAME <RET>'
     Edit a previously defined keyboard macro NAME (`edit-kbd-macro').

`C-x C-k l'
     Edit the last 300 keystrokes as a keyboard macro
     (`kmacro-edit-lossage').

   You can edit the last keyboard macro by typing `C-x C-k C-e' or `C-x
C-k RET' (`kmacro-edit-macro').  This formats the macro definition in a
buffer and enters a specialized major mode for editing it.  Type `C-h
m' once in that buffer to display details of how to edit the macro.
When you are finished editing, type `C-c C-c'.

   You can edit a named keyboard macro or a macro bound to a key by
typing `C-x C-k e' (`edit-kbd-macro').  Follow that with the keyboard
input that you would use to invoke the macro--`C-x e' or `M-x NAME' or
some other key sequence.

   You can edit the last 300 keystrokes as a macro by typing `C-x C-k
l' (`kmacro-edit-lossage').


File: emacs,  Node: Keyboard Macro Step-Edit,  Prev: Edit Keyboard Macro,  Up: Keyboard Macros

21.7 Stepwise Editing a Keyboard Macro
======================================

You can interactively replay and edit the last keyboard macro, one
command at a time, by typing `C-x C-k SPC' (`kmacro-step-edit-macro').
Unless you quit the macro using `q' or `C-g', the edited macro replaces
the last macro on the macro ring.

   This macro editing feature shows the last macro in the minibuffer
together with the first (or next) command to be executed, and prompts
you for an action.  You can enter `?' to get a summary of your options.
These actions are available:

   * `SPC' and `y' execute the current command, and advance to the next
     command in the keyboard macro.

   * `n', `d', and `DEL' skip and delete the current command.

   * `f' skips the current command in this execution of the keyboard
     macro, but doesn't delete it from the macro.

   * `<TAB>' executes the current command, as well as all similar
     commands immediately following the current command; for example,
     <TAB> may be used to insert a sequence of characters
     (corresponding to a sequence of `self-insert-command' commands).

   * `c' continues execution (without further editing) until the end of
     the keyboard macro.  If execution terminates normally, the edited
     macro replaces the original keyboard macro.

   * `C-k' skips and deletes the rest of the keyboard macro, terminates
     step-editing, and replaces the original keyboard macro with the
     edited macro.

   * `q' and `C-g' cancels the step-editing of the keyboard macro;
     discarding any changes made to the keyboard macro.

   * `i KEY... C-j' reads and executes a series of key sequences (not
     including the final `C-j'), and inserts them before the current
     command in the keyboard macro, without advancing over the current
     command.

   * `I KEY...' reads one key sequence, executes it, and inserts it
     before the current command in the keyboard macro, without advancing
     over the current command.

   * `r KEY... C-j' reads and executes a series of key sequences (not
     including the final `C-j'), and replaces the current command in
     the keyboard macro with them, advancing over the inserted key
     sequences.

   * `R KEY...' reads one key sequence, executes it, and replaces the
     current command in the keyboard macro with that key sequence,
     advancing over the inserted key sequence.

   * `a KEY... C-j' executes the current command, then reads and
     executes a series of key sequences (not including the final
     `C-j'), and inserts them after the current command in the keyboard
     macro; it then advances over the current command and the inserted
     key sequences.

   * `A KEY... C-j' executes the rest of the commands in the keyboard
     macro, then reads and executes a series of key sequences (not
     including the final `C-j'), and appends them at the end of the
     keyboard macro; it then terminates the step-editing and replaces
     the original keyboard macro with the edited macro.


File: emacs,  Node: Files,  Next: Buffers,  Prev: Keyboard Macros,  Up: Top

22 File Handling
****************

The operating system stores data permanently in named "files", so most
of the text you edit with Emacs comes from a file and is ultimately
stored in a file.

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

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

* Menu:

* File Names::          How to type and edit file-name arguments.
* Visiting::            Visiting a file prepares Emacs to edit the file.
* Saving::              Saving makes your changes permanent.
* Reverting::           Reverting cancels all the changes not saved.

* Autorevert::          Auto Reverting non-file buffers.
* Auto Save::           Auto Save periodically protects against loss of data.
* File Aliases::        Handling multiple names for one file.
* Directories::         Creating, deleting, and listing file directories.
* Comparing Files::     Finding where two files differ.
* Diff Mode::           Mode for editing file differences.
* Misc File Ops::       Other things you can do on files.
* Compressed Files::    Accessing compressed files.
* File Archives::       Operating on tar, zip, jar etc. archive files.
* Remote Files::        Accessing files on other sites.
* Quoted File Names::   Quoting special characters in file names.
* File Name Cache::     Completion against a list of files you often use.
* File Conveniences::   Convenience Features for Finding Files.
* Filesets::            Handling sets of files.


File: emacs,  Node: File Names,  Next: Visiting,  Up: Files

22.1 File Names
===============

Many Emacs commands that operate on a file require you to specify the
file name, using the minibuffer (*note Minibuffer::).  You can use
"completion" to specify long file names (*note Completion::).  Note
that file name completion ignores file names whose extensions appear in
the variable `completion-ignored-extensions' (*note Completion
Options::).

   For most operations, there is a "default file name" which is used if
you type just <RET> to enter an empty argument.  Normally, the default
file name is the name of the file visited in the current buffer.

   Each buffer has a "default directory" which is normally the same as
the directory of the file visited in that buffer.  For example, if the
default file name is `/u/rms/gnu/gnu.tasks', the default directory is
normally `/u/rms/gnu/'.  The default directory is kept in the variable
`default-directory', which has a separate value in every buffer.  When
a command reads a file name using the minibuffer, the default directory
usually serves as the initial contents of the minibuffer.  To inhibit
the insertion of the default directory, set the variable
`insert-default-directory' to `nil'.

   If you enter a file name without a directory, that specifies a file
in the default directory.  If you specify a directory in a relative
fashion, with a name that does not start with a slash, it is
interpreted with respect to the default directory.  For example,
suppose the default directory is `/u/rms/gnu/'.  Entering just `foo' in
the minibuffer, with a directory omitted, specifies the file
`/u/rms/gnu/foo'; entering `../.login' specifies `/u/rms/.login'; and
entering `new/foo' specifies `/u/rms/gnu/new/foo'.

   When typing a file name into the minibuffer, you can make use of a
couple of shortcuts: a double slash is interpreted as "ignore
everything before the second slash in the pair," and `~/' is
interpreted as your home directory.  *Note Minibuffer File::, for more
information about these shortcuts.

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

   The character `$' is used to substitute an environment variable into
a file name.  The name of the environment variable consists of all the
alphanumeric characters after the `$'; alternatively, it can be
enclosed in braces after the `$'.  For example, if you have used the
shell command `export FOO=rms/hacks' to set up an environment variable
named `FOO', then both `/u/$FOO/test.c' and `/u/${FOO}/test.c' are
abbreviations for `/u/rms/hacks/test.c'.  If the environment variable
is not defined, no substitution occurs, so that the character `$' stands
for itself.

   Note that environment variables affect Emacs only if they are
applied before Emacs is started.

   To access a file with `$' in its name, if the `$' causes expansion,
type `$$'.  This pair is converted to a single `$' at the same time
that variable substitution is performed for a single `$'.
Alternatively, quote the whole file name with `/:' (*note Quoted File
Names::).  File names which begin with a literal `~' should also be
quoted with `/:'.

   You can include non-ASCII characters in file names if you set the
variable `file-name-coding-system' to a non-`nil' value.  *Note File
Name Coding::.


File: emacs,  Node: Visiting,  Next: Saving,  Prev: File Names,  Up: Files

22.2 Visiting Files
===================

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

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

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

`C-x 4 f'
     Visit a file, in another window (`find-file-other-window').  Don't
     alter what is displayed in the selected window.

`C-x 5 f'
     Visit a file, in a new frame (`find-file-other-frame').  Don't
     alter what is displayed in the selected frame.

`M-x find-file-literally'
     Visit a file with no conversion of the contents.

   "Visiting" a file means reading its contents into an Emacs buffer so
you can edit them.  Emacs makes a new buffer for each file that you
visit.

   Emacs normally constructs the buffer name from the file name,
omitting the directory name.  For example, a file named
`/usr/rms/emacs.tex' is visited in a buffer named `emacs.tex'.  If
there is already a buffer with that name, Emacs constructs a unique
name; the normal method is to append `<2>', `<3>', and so on, but you
can select other methods.  *Note Uniquify::.

   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.  *note Mode Line::.

   The changes you make with editing commands are made in the Emacs
buffer.  They do not take effect in the file that you visited, or any
permanent place, until you "save" the buffer (*note Saving::).

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

   To visit a file, type `C-x C-f' (`find-file') and use the minibuffer
to enter the name of the desired file.  The usual defaulting and
completion behavior is available in this minibuffer (*note Minibuffer
File::).  Note, also, that completion ignores certain file names (*note
Completion Options::).  While in the minibuffer, you can abort `C-x
C-f' by typing `C-g'.

   Your can tell that `C-x C-f' has completed successfully by 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 you could not create
it, or exists but you can't read it, an error message is displayed in
the echo area.

   If you visit a file that is already in Emacs, `C-x C-f' does not make
another copy.  It selects the existing buffer containing that file.
However, before doing so, it checks whether the file itself has changed
since you visited or saved it last.  If the file has changed, Emacs
offers to reread it.

   If you try to visit a file larger than
`large-file-warning-threshold' (the default is 10000000, which is about
10 megabytes), Emacs asks you for confirmation first.  You can answer
`y' to proceed with visiting the file.  Note, however, that Emacs
cannot visit files that are larger than the maximum Emacs buffer size,
which is around 512 megabytes on 32-bit machines (*note Buffers::).  If
you try, Emacs will display an error message saying that the maximum
buffer size has been exceeded.

   If the file name you specify contains shell-style wildcard
characters, Emacs visits all the files that match it.  (On
case-insensitive filesystems, Emacs matches the wildcards disregarding
the letter case.)  Wildcards include `?', `*', and `[...]' sequences.
To enter the wild card `?' in a file name in the minibuffer, you need
to type `C-q ?'.  *Note Quoted File Names::, for information on how to
visit a file whose name actually contains wildcard characters.  You can
disable the wildcard feature by customizing `find-file-wildcards'.

   On graphical displays, there are two additional methods for visiting
files.  Firstly, when Emacs is built with a suitable GUI toolkit,
commands invoked with the mouse (by clicking on the menu bar or tool
bar) use the toolkit's standard "File Selection" dialog instead of
prompting for the file name in the minibuffer.  On GNU/Linux and Unix
platforms, Emacs does this when built with GTK, LessTif, and Motif
toolkits; on MS-Windows and Mac, the GUI version does that by default.
For information on how to customize this, see *note Dialog Boxes::.

   Secondly, Emacs supports "drag and drop": dropping a file into an
ordinary Emacs window visits the file using that window.  As an
exception, dropping a file into a window displaying a Dired buffer
moves or copies the file into the displayed directory.  For details,
see *note Drag and Drop::, and *note Misc Dired Features::.

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

   When <TAB> completion results in a nonexistent file name and you
type <RET> immediately to visit it, Emacs asks for confirmation; this
is because it's possible that you expected completion to go further and
give you an existing file's name.  The string `[Confirm]' appears for a
short time after the file name to indicate the need to confirm in this
way.  Type <RET> to confirm and visit the nonexistent file.  The
variable `confirm-nonexistent-file-or-buffer' controls whether Emacs
asks for confirmation before visiting a new file.  The default value,
`after-completion', gives the behavior we have just described.  If the
value is `nil', Emacs never asks for confirmation; for any other
non-`nil' value, Emacs always asks for confirmation.  This variable
also affects the `switch-to-buffer' command (*note Select Buffer::).
*Note Completion::, for more information about completion.

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

   If you "visit" a file that is actually a directory, Emacs invokes
Dired, the Emacs directory browser; this lets you "edit" the contents
of the directory.  *Note Dired::.  You can disable this behavior by
setting the variable `find-file-run-dired' to `nil'; in that case, it
is an error to try to visit a directory.

   Files which are actually collections of other files, or "file
archives", are visited in special modes which invoke a Dired-like
environment to allow operations on archive members.  *Note File
Archives::, for more about these features.

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

   If you want to visit a file as read-only in order to protect
yourself from entering changes accidentally, visit it with the command
`C-x C-r' (`find-file-read-only') instead of `C-x C-f'.

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

   `C-x 5 f' (`find-file-other-frame') is similar, but opens a new
frame, or makes visible any existing frame showing the file you seek.
This feature is available only when you are using a window system.
*Note Frames::.

   Emacs recognizes from the contents of a file which end-of-line
convention it uses to separate lines--newline (used on GNU/Linux and on
Unix), carriage-return linefeed (used on Microsoft systems), or just
carriage-return (used on the Macintosh)--and automatically converts the
contents to the normal Emacs convention, which is that the newline
character separates lines.  This is a part of the general feature of
coding system conversion (*note Coding Systems::), and makes it
possible to edit files imported from different operating systems with
equal convenience.  If you change the text and save the file, Emacs
performs the inverse conversion, changing newlines back into
carriage-return linefeed or just carriage-return if appropriate.

   If you wish to edit a file as a sequence of ASCII characters with no
special encoding or conversion, use the `M-x find-file-literally'
command.  This visits a file, like `C-x C-f', but does not do format
conversion (*note Formatted Text::), character code conversion (*note
Coding Systems::), or automatic uncompression (*note Compressed
Files::), and does not add a final newline because of
`require-final-newline' (*note Customize Save::).  If you have already
visited the same file in the usual (non-literal) manner, this command
asks you whether to visit it literally instead.

   Two special hook variables allow extensions to modify the operation
of visiting files.  Visiting a file that does not exist runs the
functions in the list `find-file-not-found-functions'; this variable
holds a list of functions, and the functions are called one by one
(with no arguments) until one of them returns non-`nil'.  This is not a
normal hook, and the name ends in `-functions' rather than `-hook' to
indicate that fact.

   Successful visiting of any file, whether existing or not, calls the
functions in the list `find-file-hook', with no arguments.  This
variable is a normal hook.  In the case of a nonexistent file, the
`find-file-not-found-functions' are run first.  *Note Hooks::.

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


File: emacs,  Node: Saving,  Next: Reverting,  Prev: Visiting,  Up: Files

22.3 Saving Files
=================

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

* Menu:

* Save Commands::       Commands for saving files.
* Backup::              How Emacs saves the old version of your file.
* Customize Save::      Customizing the saving of files.
* Interlocking::        How Emacs protects against simultaneous editing
                          of one file by two users.
* Shadowing: File Shadowing.  Copying files to "shadows" automatically.
* Time Stamps::         Emacs can update time stamps on saved files.


File: emacs,  Node: Save Commands,  Next: Backup,  Up: Saving

22.3.1 Commands for Saving Files
--------------------------------

These are the commands that relate to saving and writing files.

`C-x C-s'
     Save the current buffer in its visited file on disk
     (`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').
     With prefix argument (`C-u'), mark the current buffer as changed.

`C-x C-w'
     Save the current buffer with a specified file name (`write-file').

`M-x set-visited-file-name'
     Change the file 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'
displays a message like this:

     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' displays a message
like this in the echo area:

     (No changes need to be saved)

   With a prefix argument, `C-u C-x C-s', Emacs also marks the buffer
to be backed up when the next save is done.  *Note Backup::.

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

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

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

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

`<RET>'
     Terminate `save-some-buffers' without any more saving.

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

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

`d'
     Diff the buffer against its corresponding file, so you can see what
     changes you would be saving.  This calls the command
     `diff-buffer-with-file' (*note Comparing Files::).

`C-h'
     Display a help message about these options.

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

   If you have changed a buffer but do not wish to save the changes,
you should take some action to prevent it.  Otherwise, each time you
use `C-x s' or `C-x C-c', you are liable to save this buffer by
mistake.  One thing you can do is type `M-~' (`not-modified'), which
clears out the indication that the buffer is modified.  If you do this,
none of the save commands will believe that the buffer needs to be
saved.  (`~' is often used as a mathematical symbol for `not'; thus
`M-~' is `not', metafied.)  Alternatively, you can cancel all the
changes made since the file was visited or saved, by reading the text
from the file again.  This is called "reverting".  *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 reverting is easier.)

   `M-x set-visited-file-name' alters the name of the file that the
current buffer is visiting.  It reads the new file name using the
minibuffer.  Then it marks the buffer as visiting that file name, and
changes the buffer name correspondingly.  `set-visited-file-name' does
not save the buffer in the newly visited file; it just alters the
records inside Emacs in case you do save later.  It also marks the
buffer as "modified" so that `C-x C-s' in that buffer _will_ save.

   If you wish to mark the buffer as visiting a different file and save
it right away, use `C-x C-w' (`write-file').  This is equivalent to
`set-visited-file-name' followed by `C-x C-s', except that `C-x C-w'
asks for confirmation if the file exists.  `C-x C-s' used on a buffer
that is not visiting 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 (*note File Names::).

   If the new file name implies a major mode, then `C-x C-w' switches
to that major mode, in most cases.  The command `set-visited-file-name'
also does this.  *Note Choosing Modes::.

   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.


File: emacs,  Node: Backup,  Next: Customize Save,  Prev: Save Commands,  Up: Saving

22.3.2 Backup Files
-------------------

On most operating systems, rewriting a file 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.

   Emacs makes a backup for a file only the first time the file is
saved from a buffer.  No matter how many times you subsequently save
the file, its backup remains unchanged.  However, if you kill the
buffer and then visit the file again, a new backup file will be made.

   For most files, the variable `make-backup-files' determines whether
to make backup files.  On most operating systems, its default value is
`t', so that Emacs does write backup files.

   For files managed by a version control system (*note Version
Control::), the variable `vc-make-backup-files' determines whether to
make backup files.  By default it is `nil', since backup files are
redundant when you store all the previous versions in a version control
system.  *Note General VC Options::.

   At your option, Emacs can keep either a single backup for each file,
or make a series of numbered backup files for each file that you edit.
*Note Backup Names::.

   The default value of the `backup-enable-predicate' variable prevents
backup files being written for files in the directories used for
temporary files, specified by `temporary-file-directory' or
`small-temporary-file-directory'.

   You can explicitly tell Emacs to make another backup file from a
buffer, even though that buffer has been saved before.  If you save the
buffer with `C-u C-x C-s', the version thus saved will be made into a
backup file if you save the buffer again.  `C-u C-u C-x C-s' saves the
buffer, but first makes the previous file contents into a new backup
file.  `C-u C-u C-u C-x C-s' does both things: it makes a backup from
the previous contents, and arranges to make another from the newly
saved contents if you save again.

* Menu:

* Names: Backup Names.          How backup files are named.
* 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,  Up: Backup

22.3.2.1 Single or Numbered Backups
...................................

When Emacs makes a backup file, its name is normally constructed by
appending `~' to the file name being edited; thus, the backup file for
`eval.c' would be `eval.c~'.

   If access control stops Emacs from writing backup files under the
usual names, it writes the backup file as `~/.emacs.d/%backup%~'.  Only
one such file can exist, so only the most recently made such backup is
available.

   Emacs can also make "numbered backup files".  Numbered backup file
names contain `.~', the number, and another `~' after the original file
name.  Thus, the backup files of `eval.c' would be called `eval.c.~1~',
`eval.c.~2~', and so on, all the way through names like `eval.c.~259~'
and beyond.

   The variable `version-control' determines whether to make single
backup files or multiple numbered backup files.  Its possible values
are:

`nil'
     Make numbered backups for files that have numbered backups already.
     Otherwise, make single backups.  This is the default.

`t'
     Make numbered backups.

`never'
     Never make numbered backups; always make single backups.

The usual way to set this variable is globally, through your `.emacs'
file or the customization buffer.  However, you can set
`version-control' locally in an individual buffer to control the making
of backups for that buffer's file (*note Locals::).  You can have Emacs
set `version-control' locally whenever you visit a given file (*note
File Variables::).  Some modes, such as Rmail mode, set this variable.

   If you set the environment variable `VERSION_CONTROL', to tell
various GNU utilities what to do with backup files, Emacs also obeys the
environment variable by setting the Lisp variable `version-control'
accordingly at startup.  If the environment variable's value is `t' or
`numbered', then `version-control' becomes `t'; if the value is `nil'
or `existing', then `version-control' becomes `nil'; if it is `never'
or `simple', then `version-control' becomes `never'.

   You can customize the variable `backup-directory-alist' to specify
that files matching certain patterns should be backed up in specific
directories.  This variable applies to both single and numbered
backups.  A typical use is to add an element `("."  . DIR)' to make all
backups in the directory with absolute name DIR; Emacs modifies the
backup file names to avoid clashes between files with the same names
originating in different directories.  Alternatively, adding, `("." .
".~")' would make backups in the invisible subdirectory `.~' of the
original file's directory.  Emacs creates the directory, if necessary,
to make the backup.

   If you define the variable `make-backup-file-name-function' to a
suitable Lisp function, that overrides the usual way Emacs constructs
backup file names.


File: emacs,  Node: Backup Deletion,  Next: Backup Copying,  Prev: Backup Names,  Up: Backup

22.3.2.2 Automatic Deletion of Backups
......................................

To prevent excessive consumption of disk space, Emacs can delete
numbered backup versions automatically.  Generally Emacs keeps the
first few backups and the latest few backups, deleting any in between.
This happens every time a new backup is made.

   The two variables `kept-old-versions' and `kept-new-versions'
control this deletion.  Their values are, respectively, the number of
oldest (lowest-numbered) backups to keep and the number of newest
(highest-numbered) ones to keep, each time a new backup is made.  The
backups in the middle (excluding those oldest and newest) are the
excess middle versions--those backups are deleted.  These variables'
values are used when it is time to delete excess versions, just after a
new backup version is made; the newly made backup is included in the
count in `kept-new-versions'.  By default, both variables are 2.

   If `delete-old-versions' is `t', Emacs deletes the excess backup
files silently.  If it is `nil', the default, Emacs asks you whether it
should delete the excess backup versions.  If it has any other value,
then Emacs never automatically deletes backups.

   Dired's `.' (Period) command can also be used to delete old versions.
*Note Dired Deletion::.


File: emacs,  Node: Backup Copying,  Prev: Backup Deletion,  Up: Backup

22.3.2.3 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 (hard
links).  If the old file is renamed into the backup file, then the
alternate names become names for the backup file.  If the old file is
copied instead, then the alternate names remain names for the file that
you are editing, and the contents accessed by those names will be the
new contents.

   The method of making a backup file may also affect the file's owner
and group.  If copying is used, these do not change.  If renaming is
used, you become the file's owner, and the file's group becomes the
default (different operating systems have different defaults for the
group).

   Having the owner change is usually a good idea, because then the
owner always shows who last edited the file.  Also, the owners of the
backups show who produced those versions.  Occasionally there is a file
whose owner should not change; it is a good idea for such files to
contain local variable lists to set `backup-by-copying-when-mismatch'
locally (*note File Variables::).

   The choice of renaming or copying is controlled by four variables.
Renaming is the default choice.  If the variable `backup-by-copying' is
non-`nil', copying is used.  Otherwise, if the variable
`backup-by-copying-when-linked' is non-`nil', then copying is used for
files that have multiple names, but renaming may still be used when the
file being edited has only one name.  If the variable
`backup-by-copying-when-mismatch' is non-`nil', then copying is used if
renaming would cause the file's owner or group to change.
`backup-by-copying-when-mismatch' is `t' by default if you start Emacs
as the superuser.  The fourth variable,
`backup-by-copying-when-privileged-mismatch', gives the highest numeric
user-id for which `backup-by-copying-when-mismatch' will be forced on.
This is useful when low-numbered user-ids are assigned to special
system users, such as `root', `bin', `daemon', etc., which must
maintain ownership of files.

   When a file is managed with a version control system (*note Version
Control::), Emacs does not normally make backups in the usual way for
that file.  But check-in and check-out are similar in some ways to
making backups.  One unfortunate similarity is that these operations
typically break hard links, disconnecting the file name you visited from
any alternate names for the same file.  This has nothing to do with
Emacs--the version control system does it.


File: emacs,  Node: Customize Save,  Next: Interlocking,  Prev: Backup,  Up: Saving

22.3.3 Customizing Saving of Files
----------------------------------

If the value of the variable `require-final-newline' is `t', saving or
writing a file silently puts a newline at the end if there isn't
already one there.  If the value is `visit', Emacs adds a newline at
the end of any file that doesn't have one, just after it visits the
file.  (This marks the buffer as modified, and you can undo it.)  If
the value is `visit-save', that means to add newlines both on visiting
and on saving.  If the value is `nil', Emacs leaves the end of the file
unchanged; if it's neither `nil' nor `t', Emacs asks you whether to add
a newline.  The default is `nil'.

   Many major modes are designed for specific kinds of files that are
always supposed to end in newlines.  These major modes set the variable
`require-final-newline' according to `mode-require-final-newline'.  By
setting the latter variable, you can control how these modes handle
final newlines.

   When Emacs saves a file, it invokes the `fsync' system call to force
the data immediately out to disk.  This is important for safety if the
system crashes or in case of power outage.  However, it can be
disruptive on laptops using power saving, because it requires the disk
to spin up each time you save a file.  Setting
`write-region-inhibit-fsync' to a non-`nil' value disables this
synchronization.  Be careful--this means increased risk of data loss.


File: emacs,  Node: Interlocking,  Next: File Shadowing,  Prev: Customize Save,  Up: Saving

22.3.4 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.  On all
systems, Emacs checks when you save the file, and warns if you are
about to overwrite another user's changes.  You can prevent loss of the
other user's work by taking the proper corrective action instead of
saving the file.

   When you make the first modification in an Emacs buffer that is
visiting a file, Emacs records that the file is "locked" by you.  (It
does this by creating a specially-named symbolic link in the same
directory.)  Emacs removes the lock when you save the changes.  The
idea is that the file is locked whenever an Emacs buffer visiting it
has unsaved changes.

   If you begin to modify the buffer while the visited file is locked by
someone else, this constitutes a "collision".  When Emacs detects a
collision, it asks you what to do, by calling the Lisp function
`ask-user-about-lock'.  You can redefine this function for the sake of
customization.  The standard definition of this function asks you a
question and accepts three possible answers:

`s'
     Steal the lock.  Whoever was already changing the file loses the
     lock, and you gain the lock.

`p'
     Proceed.  Go ahead and edit the file despite its being locked by
     someone else.

`q'
     Quit.  This causes an error (`file-locked'), and the buffer
     contents remain unchanged--the modification you were trying to make
     does not actually take place.

   Note that locking works on the basis of a file name; if a file has
multiple names, Emacs does not realize that the two names are the same
file and cannot prevent two users from editing it simultaneously under
different names.  However, basing locking on names means that Emacs can
interlock the editing of new files that will not really exist until
they are saved.

   Some systems are not configured to allow Emacs to make locks, and
there are cases where lock files cannot be written.  In these cases,
Emacs cannot detect trouble in advance, but it still can detect the
collision when you try to save a file and overwrite someone else's
changes.  Every time Emacs saves a buffer, it first checks the
last-modification date of the existing file on disk to verify that it
has not changed since the file was last visited or saved.  If the date
does not match, it implies that changes were made in the file in some
other way, and these changes are about to be lost if Emacs actually
does save.  To prevent this, Emacs displays 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.

   If Emacs or the operating system crashes, this may leave behind lock
files which are stale, so you may occasionally get warnings about
spurious collisions.  When you determine that the collision is spurious,
just use `p' to tell Emacs to go ahead anyway.

   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 Directories::).  This shows the file's current author.  You
should attempt to contact him to warn him not to continue editing.
Often the next step is to save the contents of your Emacs buffer under a
different name, and use `diff' to compare the two files.


File: emacs,  Node: File Shadowing,  Next: Time Stamps,  Prev: Interlocking,  Up: Saving

22.3.5 Shadowing Files
----------------------

`M-x shadow-initialize'
     Set up file shadowing.

`M-x shadow-define-literal-group'
     Declare a single file to be shared between sites.

`M-x shadow-define-regexp-group'
     Make all files that match each of a group of files be shared
     between hosts.

`M-x shadow-define-cluster <RET> NAME <RET>'
     Define a shadow file cluster NAME.

`M-x shadow-copy-files'
     Copy all pending shadow files.

`M-x shadow-cancel'
     Cancel the instruction to shadow some files.

   You can arrange to keep identical "shadow" copies of certain files
in more than one place--possibly on different machines.  To do this,
first you must set up a "shadow file group", which is a set of
identically-named files shared between a list of sites.  The file group
is permanent and applies to further Emacs sessions as well as the
current one.  Once the group is set up, every time you exit Emacs, it
will copy the file you edited to the other files in its group.  You can
also do the copying without exiting Emacs, by typing `M-x
shadow-copy-files'.

   To set up a shadow file group, use `M-x shadow-define-literal-group'
or `M-x shadow-define-regexp-group'.  See their documentation strings
for further information.

   Before copying a file to its shadows, Emacs asks for confirmation.
You can answer "no" to bypass copying of this file, this time.  If you
want to cancel the shadowing permanently for a certain file, use `M-x
shadow-cancel' to eliminate or change the shadow file group.

   A "shadow cluster" is a group of hosts that share directories, so
that copying to or from one of them is sufficient to update the file on
all of them.  Each shadow cluster has a name, and specifies the network
address of a primary host (the one we copy files to), and a regular
expression that matches the host names of all the other hosts in the
cluster.  You can define a shadow cluster with `M-x
shadow-define-cluster'.


File: emacs,  Node: Time Stamps,  Prev: File Shadowing,  Up: Saving

22.3.6 Updating Time Stamps Automatically
-----------------------------------------

You can arrange to put a time stamp in a file, so that it will be
updated automatically each time you edit and save the file.  The time
stamp has to be in the first eight lines of the file, and you should
insert it like this:

     Time-stamp: <>

or like this:

     Time-stamp: " "

   Then add the hook function `time-stamp' to the hook
`before-save-hook'; that hook function will automatically update the
time stamp, inserting the current date and time when you save the file.
You can also use the command `M-x time-stamp' to update the time stamp
manually.  For other customizations, see the Custom group `time-stamp'.
Note that non-numeric fields in the time stamp are formatted according
to your locale setting (*note Environment::).


File: emacs,  Node: Reverting,  Next: Autorevert,  Prev: Saving,  Up: Files

22.4 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 reverting a buffer unintentionally could lose
a lot of work, you must confirm this command with `yes'.

   `revert-buffer' tries to position point in such a way that, if the
file was edited only slightly, you will be at approximately the same
piece of text after reverting as before.  However, if you have made
drastic changes, point may wind up in a totally different piece of text.

   Reverting marks the buffer as "not modified".

   Some kinds of buffers that are not associated with files, such as
Dired buffers, can also be reverted.  For them, reverting means
recalculating their contents.  Buffers created explicitly with `C-x b'
cannot be reverted; `revert-buffer' reports an error if you try.

   When you edit a file that changes automatically and frequently--for
example, a log of output from a process that continues to run--it may
be useful for Emacs to revert the file without querying you.  To
request this behavior, set the variable `revert-without-query' to a
list of regular expressions.  When a file name matches one of these
regular expressions, `find-file' and `revert-buffer' will revert it
automatically if it has changed--provided the buffer itself is not
modified.  (If you have edited the text, it would be wrong to discard
your changes.)

   In addition, you can tell Emacs to periodically revert a buffer by
typing `M-x auto-revert-mode'.  This turns on Auto-Revert mode, a minor
mode that makes Emacs automatically revert the current buffer every
five seconds.  You can change this interval through the variable
`auto-revert-interval'.  Typing `M-x global-auto-revert-mode' enables
Global Auto-Revert mode, which does the same for all file buffers.
Auto-Revert mode and Global Auto-Revert modes do not check or revert
remote files, because that is usually too slow.

   One use of Auto-Revert mode is to "tail" a file such as a system
log, so that changes made to that file by other programs are
continuously displayed.  To do this, just move the point to the end of
the buffer, and it will stay there as the file contents change.
However, if you are sure that the file will only change by growing at
the end, use Auto-Revert Tail mode instead (`auto-revert-tail-mode').
It is more efficient for this.  Auto-Revert Tail mode works also for
remote files.

   *Note VC Mode Line::, for Auto Revert peculiarities in buffers that
visit files under version control.


File: emacs,  Node: Autorevert,  Next: Auto Save,  Prev: Reverting,  Up: Files

22.5 Auto Reverting Non-File Buffers
====================================

Global Auto Revert Mode normally only reverts file buffers.  There are
two ways to auto-revert certain non-file buffers: enabling Auto Revert
Mode in those buffers (using `M-x auto-revert-mode'); and setting
`global-auto-revert-non-file-buffers' non-`nil'.  The latter enables
Auto Reverting for all types of buffers for which it is implemented
(listed in the menu below).

   Like file buffers, non-file buffers should normally not revert while
you are working on them, or while they contain information that might
get lost after reverting.  Therefore, they do not revert if they are
"modified".  This can get tricky, because deciding when a non-file
buffer should be marked modified is usually more difficult than for
file buffers.

   Another tricky detail is that, for efficiency reasons, Auto Revert
often does not try to detect all possible changes in the buffer, only
changes that are "major" or easy to detect.  Hence, enabling
auto-reverting for a non-file buffer does not always guarantee that all
information in the buffer is up-to-date, and does not necessarily make
manual reverts useless.

   At the other extreme, certain buffers automatically revert every
`auto-revert-interval' seconds.  (This currently only applies to the
Buffer Menu.)  In this case, Auto Revert does not print any messages
while reverting, even when `auto-revert-verbose' is non-`nil'.

   The details depend on the particular types of buffers and are
explained in the corresponding sections.

* Menu:

* Auto Reverting the Buffer Menu:: Auto Revert of the Buffer Menu.
* Auto Reverting Dired::           Auto Revert of Dired buffers.
* Supporting additional buffers::  How to add more Auto Revert support.


File: emacs,  Node: Auto Reverting the Buffer Menu,  Next: Auto Reverting Dired,  Up: Autorevert

22.5.1 Auto Reverting the Buffer Menu
-------------------------------------

If auto-reverting of non-file buffers is enabled, the Buffer Menu
automatically reverts every `auto-revert-interval' seconds, whether
there is a need for it or not.  (It would probably take longer to check
whether there is a need than to actually revert.)

   If the Buffer Menu inappropriately gets marked modified, just revert
it manually using `g' and auto-reverting will resume.  However, if you
marked certain buffers to get deleted or to be displayed, you have to
be careful, because reverting erases all marks.  The fact that adding
marks sets the buffer's modified flag prevents Auto Revert from
automatically erasing the marks.


File: emacs,  Node: Auto Reverting Dired,  Next: Supporting additional buffers,  Prev: Auto Reverting the Buffer Menu,  Up: Autorevert

22.5.2 Auto Reverting Dired buffers
-----------------------------------

Auto-reverting Dired buffers currently works on GNU or Unix style
operating systems.  It may not work satisfactorily on some other
systems.

   Dired buffers only auto-revert when the file list of the buffer's
main directory changes (e.g. when a new file is added).  They do not
auto-revert when information about a particular file changes (e.g. when
the size changes) or when inserted subdirectories change.  To be sure
that _all_ listed information is up to date, you have to manually
revert using `g', _even_ if auto-reverting is enabled in the Dired
buffer.  Sometimes, you might get the impression that modifying or
saving files listed in the main directory actually does cause
auto-reverting.  This is because making changes to a file, or saving
it, very often causes changes in the directory itself; for instance,
through backup files or auto-save files.  However, this is not
guaranteed.

   If the Dired buffer is marked modified and there are no changes you
want to protect, then most of the time you can make auto-reverting
resume by manually reverting the buffer using `g'.  There is one
exception.  If you flag or mark files, you can safely revert the
buffer.  This will not erase the flags or marks (unless the marked file
has been deleted, of course).  However, the buffer will stay modified,
even after reverting, and auto-reverting will not resume.  This is
because, if you flag or mark files, you may be working on the buffer
and you might not want the buffer to change without warning.  If you
want auto-reverting to resume in the presence of marks and flags, mark
the buffer non-modified using `M-~'.  However, adding, deleting or
changing marks or flags will mark it modified again.

   Remote Dired buffers are not auto-reverted (because it may be slow).
Neither are Dired buffers for which you used shell wildcards or file
arguments to list only some of the files.  `*Find*' and `*Locate*'
buffers do not auto-revert either.


File: emacs,  Node: Supporting additional buffers,  Prev: Auto Reverting Dired,  Up: Autorevert

22.5.3 Adding Support for Auto-Reverting additional Buffers.
------------------------------------------------------------

This section is intended for Elisp programmers who would like to add
support for auto-reverting new types of buffers.

   To support auto-reverting the buffer must first of all have a
`revert-buffer-function'.  *Note Reverting: (elisp)Definition of
revert-buffer-function.

   In addition, it _must_ have a `buffer-stale-function'.

 -- Variable: buffer-stale-function
     The value of this variable is a function to check whether a
     non-file buffer needs reverting.  This should be a function with
     one optional argument NOCONFIRM.  The function should return
     non-`nil' if the buffer should be reverted.  The buffer is current
     when this function is called.

     While this function is mainly intended for use in auto-reverting,
     it could be used for other purposes as well.  For instance, if
     auto-reverting is not enabled, it could be used to warn the user
     that the buffer needs reverting.  The idea behind the NOCONFIRM
     argument is that it should be `t' if the buffer is going to be
     reverted without asking the user and `nil' if the function is just
     going to be used to warn the user that the buffer is out of date.
     In particular, for use in auto-reverting, NOCONFIRM is `t'.  If
     the function is only going to be used for auto-reverting, you can
     ignore the NOCONFIRM argument.

     If you just want to automatically auto-revert every
     `auto-revert-interval' seconds (like the Buffer Menu), use:

          (set (make-local-variable 'buffer-stale-function)
               #'(lambda (&optional noconfirm) 'fast))

     in the buffer's mode function.

     The special return value `fast' tells the caller that the need for
     reverting was not checked, but that reverting the buffer is fast.
     It also tells Auto Revert not to print any revert messages, even if
     `auto-revert-verbose' is non-`nil'.  This is important, as getting
     revert messages every `auto-revert-interval' seconds can be very
     annoying.  The information provided by this return value could
     also be useful if the function is consulted for purposes other than
     auto-reverting.

   Once the buffer has a `revert-buffer-function' and a
`buffer-stale-function', several problems usually remain.

   The buffer will only auto-revert if it is marked unmodified.  Hence,
you will have to make sure that various functions mark the buffer
modified if and only if either the buffer contains information that
might be lost by reverting, or there is reason to believe that the user
might be inconvenienced by auto-reverting, because he is actively
working on the buffer.  The user can always override this by manually
adjusting the modified status of the buffer.  To support this, calling
the `revert-buffer-function' on a buffer that is marked unmodified
should always keep the buffer marked unmodified.

   It is important to assure that point does not continuously jump
around as a consequence of auto-reverting.  Of course, moving point
might be inevitable if the buffer radically changes.

   You should make sure that the `revert-buffer-function' does not
print messages that unnecessarily duplicate Auto Revert's own messages,
displayed if `auto-revert-verbose' is `t', and effectively override a
`nil' value for `auto-revert-verbose'.  Hence, adapting a mode for
auto-reverting often involves getting rid of such messages.  This is
especially important for buffers that automatically revert every
`auto-revert-interval' seconds.

   If the new auto-reverting is part of Emacs, you should mention it in
the documentation string of `global-auto-revert-non-file-buffers'.

   Similarly, you should add a node to this chapter's menu.  This node
should at the very least make clear whether enabling auto-reverting for
the buffer reliably assures that all information in the buffer is
completely up to date (or will be after `auto-revert-interval' seconds).


File: emacs,  Node: Auto Save,  Next: File Aliases,  Prev: Autorevert,  Up: Files

22.6 Auto-Saving: Protection Against Disasters
==============================================

From time to time, Emacs automatically saves each visited file in a
separate file, without altering the file you actually use.  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, it considers
each buffer, and each is auto-saved if auto-saving is enabled for it
and it has been changed since the last time it was auto-saved.  The
message `Auto-saving...' is displayed in the echo area during
auto-saving, if any files are actually auto-saved.  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.       The file where auto-saved changes are
                                  actually made until you save the file.
* Control: Auto Save Control.   Controlling when and how often to auto-save.
* Recover::                     Recovering text from auto-save files.


File: emacs,  Node: Auto Save Files,  Next: Auto Save Control,  Up: Auto Save

22.6.1 Auto-Save Files
----------------------

Auto-saving does not normally save in the files that you visited,
because it can be very undesirable to save a change that you did not
want to make permanent.  Instead, auto-saving is done in a different
file called the "auto-save file", and the visited file is changed only
when you request saving explicitly (such as with `C-x C-s').

   Normally, the auto-save file name is made by appending `#' to the
front and rear of the visited file name.  Thus, a buffer visiting file
`foo.c' is auto-saved in a file `#foo.c#'.  Most buffers that are not
visiting files are auto-saved only if you request it explicitly; when
they are auto-saved, the auto-save file name is made by appending `#'
to the front and rear of buffer name, then adding digits and letters at
the end for uniqueness.  For example, the `*mail*' buffer in which you
compose messages to be sent might be auto-saved in a file named
`#*mail*#704juu'.  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.

   The variable `auto-save-file-name-transforms' allows a degree of
control over the auto-save file name.  It lets you specify a series of
regular expressions and replacements to transform the auto save file
name.  The default value puts the auto-save files for remote files
(*note Remote Files::) into the temporary file directory on the local
machine.

   When you delete a substantial part of the text in a large buffer,
auto save turns off temporarily in that buffer.  This is because if you
deleted the text unintentionally, you might find the auto-save file more
useful if it contains the deleted text.  To reenable auto-saving after
this happens, save the buffer with `C-x C-s', or use `C-u 1 M-x
auto-save-mode'.

   If you want auto-saving to be done in the visited file rather than
in a separate auto-save file, set the variable
`auto-save-visited-file-name' to a non-`nil' value.  In this mode,
there is no real difference between auto-saving and explicit saving.

   A buffer's auto-save file is deleted when you save the buffer in its
visited file.  (You can inhibit this by setting 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

22.6.2 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 doesn't accept
values that are too small: if you customize `auto-save-interval' to a
value less than 20, Emacs will behave as if the value is 20.

   Auto-saving also takes place when you stop typing for a while.  The
variable `auto-save-timeout' says how many seconds Emacs should wait
before it does an auto save (and perhaps also a garbage collection).
(The actual time period is longer if the current buffer is long; this
is a heuristic which aims to keep out of your way when you are editing
long buffers, in which auto-save takes an appreciable amount of time.)
Auto-saving during idle periods accomplishes two things: first, it
makes sure all your work is saved if you go away from the terminal for
a while; second, it may avoid some auto-saving while you are actually
typing.

   Emacs also does auto-saving whenever it gets a fatal error.  This
includes killing the Emacs job with a shell command such as `kill
%emacs', or disconnecting a phone line or network connection.

   You can request an auto-save explicitly with the command `M-x
do-auto-save'.


File: emacs,  Node: Recover,  Prev: Auto Save Control,  Up: Auto Save

22.6.3 Recovering Data from Auto-Saves
--------------------------------------

You can use the contents of an auto-save file to recover from a loss of
data with the command `M-x recover-file <RET> FILE <RET>'.  This visits
FILE and then (after your confirmation) restores the contents from its
auto-save file `#FILE#'.  You can then save with `C-x C-s' to put the
recovered text into FILE itself.  For example, to recover file `foo.c'
from its auto-save file `#foo.c#', do:

     M-x recover-file <RET> foo.c <RET>
     yes <RET>
     C-x C-s

   Before asking for confirmation, `M-x recover-file' displays a
directory listing describing the specified file and the auto-save file,
so you can compare their sizes and dates.  If the auto-save file is
older, `M-x recover-file' does not offer to read it.

   If Emacs or the computer crashes, you can recover all the files you
were editing from their auto save files with the command `M-x
recover-session'.  This first shows you a list of recorded interrupted
sessions.  Move point to the one you choose, and type `C-c C-c'.

   Then `recover-session' asks about each of the files that were being
edited during that session, asking whether to recover that file.  If
you answer `y', it calls `recover-file', which works in its normal
fashion.  It shows the dates of the original file and its auto-save
file, and asks once again whether to recover that file.

   When `recover-session' is done, the files you've chosen to recover
are present in Emacs buffers.  You should then save them.  Only
this--saving them--updates the files themselves.

   Emacs records information about interrupted sessions for later
recovery in files named
`~/.emacs.d/auto-save-list/.saves-PID-HOSTNAME'.  The directory used,
`~/.emacs.d/auto-save-list/', is determined by the variable
`auto-save-list-file-prefix'.  You can record sessions in a different
place by customizing that variable.  If you set
`auto-save-list-file-prefix' to `nil' in your `.emacs' file, sessions
are not recorded for recovery.


File: emacs,  Node: File Aliases,  Next: Directories,  Prev: Auto Save,  Up: Files

22.7 File Name Aliases
======================

Symbolic links and hard links both make it possible for several file
names to refer to the same file.  Hard links are alternate names that
refer directly to the file; all the names are equally valid, and no one
of them is preferred.  By contrast, a symbolic link is a kind of defined
alias: when `foo' is a symbolic link to `bar', you can use either name
to refer to the file, but `bar' is the real name, while `foo' is just
an alias.  More complex cases occur when symbolic links point to
directories.

   Normally, if you visit a file which Emacs is already visiting under
a different name, Emacs displays a message in the echo area and uses
the existing buffer visiting that file.  This can happen on systems
that support hard or symbolic links, or if you use a long file name on
a system that truncates long file names, or on a case-insensitive file
system.  You can suppress the message by setting the variable
`find-file-suppress-same-file-warnings' to a non-`nil' value.  You can
disable this feature entirely by setting the variable
`find-file-existing-other-name' to `nil': then if you visit the same
file under two different names, you get a separate buffer for each file
name.

   If the variable `find-file-visit-truename' is non-`nil', then the
file name recorded for a buffer is the file's "truename" (made by
replacing all symbolic links with their target names), rather than the
name you specify.  Setting `find-file-visit-truename' also implies the
effect of `find-file-existing-other-name'.

   Sometimes, a directory is ordinarily accessed through a symbolic
link, and you may want Emacs to preferentially show its "linked" name.
To do this, customize `directory-abbrev-alist'.  Each element in this
list should have the form `(FROM . TO)', which means to replace FROM
with TO whenever FROM appears in a directory name.  The FROM string is a
regular expression (*note Regexps::).  It is matched against directory
names anchored at the first character, and should start with `\`' (to
support directory names with embedded newlines, which would defeat
`^').  The TO string should be an ordinary absolute directory name
pointing to the same directory.  Do not use `~' to stand for a home
directory in the TO string; Emacs performs these substitutions
separately.  Here's an example, from a system on which `/home/fsf' is
normally accessed through a symbolic link named `/fsf':

     (("\\`/home/fsf" . "/fsf"))


File: emacs,  Node: Directories,  Next: Comparing Files,  Prev: File Aliases,  Up: Files

22.8 File Directories
=====================

The file system groups files into "directories".  A "directory listing"
is a list of all the files in a directory.  Emacs provides commands to
create and delete directories, and to make directory listings in brief
format (file names only) and verbose format (sizes, dates, and authors
included).  Emacs also includes a directory browser feature called
Dired; see *note Dired::.

`C-x C-d DIR-OR-PATTERN <RET>'
     Display a brief directory listing (`list-directory').

`C-u C-x C-d DIR-OR-PATTERN <RET>'
     Display a verbose directory listing.

`M-x make-directory <RET> DIRNAME <RET>'
     Create a new directory named DIRNAME.

`M-x delete-directory <RET> DIRNAME <RET>'
     Delete the directory named DIRNAME.  If it isn't empty, you will
     be asked whether you want to delete it recursively.

   The command to display a directory listing is `C-x C-d'
(`list-directory').  It reads using the minibuffer a file name which is
either a directory to be listed or a wildcard-containing pattern for
the files to be listed.  For example,

     C-x C-d /u2/emacs/etc <RET>

lists all the files in directory `/u2/emacs/etc'.  Here is an example
of specifying a file name pattern:

     C-x C-d /u2/emacs/src/*.c <RET>

   Normally, `C-x C-d' displays a brief directory listing containing
just file names.  A numeric argument (regardless of value) tells it to
make a verbose listing including sizes, dates, and owners (like `ls
-l').

   The text of a directory listing is mostly 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).

   In verbose directory listings, Emacs adds information about the
amount of free space on the disk that contains the directory.  To do
this, it runs the program specified by `directory-free-space-program'
with arguments `directory-free-space-args'.

   The command `M-x delete-directory' prompts for a directory name
using the minibuffer, and deletes the directory if it is empty.  If the
directory is not empty, you will be asked whether you want to delete it
recursively.  On systems that have a "Trash" or "Recycle Bin" feature,
you can make this command move the specified directory to the Trash or
Recycle Bin, instead of deleting it outright, by changing the variable
`delete-by-moving-to-trash' to `t'.  *Note Misc File Ops::, for more
information about using the Trash.


File: emacs,  Node: Comparing Files,  Next: Diff Mode,  Prev: Directories,  Up: Files

22.9 Comparing Files
====================

The command `M-x diff' prompts for two file names, using the
minibuffer, and displays the differences between the two files in a
buffer named `*diff*'.  This works by running the `diff' program, using
options taken from the variable `diff-switches'.  The value of
`diff-switches' should be a string; the default is `"-c"' to specify a
context diff.  *Note Diff: (diff)Top, for more information about `diff'
output formats.

   The output of the `diff' command is shown using a major mode called
Diff mode.  *Note Diff Mode::.

   The command `M-x diff-backup' compares a specified file with its
most recent backup.  If you specify the name of a backup file,
`diff-backup' compares it with the source file that it is a backup of.
In all other respects, this behaves like `M-x diff'.

   The command `M-x diff-buffer-with-file' compares a specified buffer
with its corresponding file.  This shows you what changes you would
make to the file if you save the buffer.

   The command `M-x compare-windows' compares the text in the current
window with that in the next window.  (For more information about
windows in Emacs, *note Windows::.)  Comparison starts at point in each
window, after pushing each initial point value on the mark ring in its
respective buffer.  Then it moves point forward in each window, one
character at a time, until it reaches characters that don't match.
Then the command exits.

   If point in the two windows is followed by non-matching text when
the command starts, `M-x compare-windows' tries heuristically to
advance up to matching text in the two windows, and then exits.  So if
you use `M-x compare-windows' repeatedly, each time it either skips one
matching range or finds the start of another.

   With a numeric argument, `compare-windows' ignores changes in
whitespace.  If the variable `compare-ignore-case' is non-`nil', the
comparison ignores differences in case as well.  If the variable
`compare-ignore-whitespace' is non-`nil', `compare-windows' normally
ignores changes in whitespace, and a prefix argument turns that off.

   You can use `M-x smerge-mode' to turn on Smerge mode, a minor mode
for editing output from the `diff3' program.  This is typically the
result of a failed merge from a version control system "update" outside
VC, due to conflicting changes to a file.  Smerge mode provides
commands to resolve conflicts by selecting specific changes.

   *Note Emerge::, for the Emerge facility, which provides a powerful
interface for merging files.


File: emacs,  Node: Diff Mode,  Next: Misc File Ops,  Prev: Comparing Files,  Up: Files

22.10 Diff Mode
===============

Diff mode is a major mode used for the output of `M-x diff' and other
similar commands, as well as the output of the `diff' program.  This
kind of output is called a "patch", because it can be passed to the
`patch' command to automatically apply the specified changes.  To
select Diff mode manually, type `M-x diff-mode'.

   The changes specified in a patch are grouped into "hunks", which are
contiguous chunks of text that contain one or more changed lines.
Hunks can also include unchanged lines to provide context for the
changes.  Each hunk is preceded by a "hunk header", which specifies the
old and new line numbers at which the hunk occurs.  Diff mode
highlights each hunk header, to distinguish it from the actual contents
of the hunk.

   You can edit a Diff mode buffer like any other buffer.  (If it is
read-only, you need to make it writable first.  *Note Misc Buffer::.)
Whenever you change a hunk, Diff mode attempts to automatically correct
the line numbers in the hunk headers, to ensure that the diff remains
"correct".  To disable automatic line number correction, change the
variable `diff-update-on-the-fly' to `nil'.

   Diff mode treats each hunk as an "error message," similar to
Compilation mode.  Thus, you can use commands such as `C-x '' to visit
the corresponding source locations.  *Note Compilation Mode::.

   In addition, Diff mode provides the following commands to navigate,
manipulate and apply parts of patches:

`M-n'
     Move to the next hunk-start (`diff-hunk-next').

`M-p'
     Move to the previous hunk-start (`diff-hunk-prev').

`M-}'
     Move to the next file-start, in a multi-file patch
     (`diff-file-next').

`M-{'
     Move to the previous file-start, in a multi-file patch
     (`diff-file-prev').

`M-k'
     Kill the hunk at point (`diff-hunk-kill').

`M-K'
     In a multi-file patch, kill the current file part.
     (`diff-file-kill').

`C-c C-a'
     Apply this hunk to its target file (`diff-apply-hunk').  With a
     prefix argument of `C-u', revert this hunk.

`C-c C-b'
     Highlight the changes of the hunk at point with a finer granularity
     (`diff-refine-hunk').  This allows you to see exactly which parts
     of each changed line were actually changed.

`C-c C-c'
     Go to the source file and line corresponding to this hunk
     (`diff-goto-source').

`C-c C-e'
     Start an Ediff session with the patch (`diff-ediff-patch').  *Note
     Ediff: (ediff)Top.

`C-c C-n'
     Restrict the view to the current hunk (`diff-restrict-view').
     *Note Narrowing::.  With a prefix argument of `C-u', restrict the
     view to the current file of a multiple-file patch.  To widen again,
     use `C-x n w' (`widen').

`C-c C-r'
     Reverse the direction of comparison for the entire buffer
     (`diff-reverse-direction').

`C-c C-s'
     Split the hunk at point (`diff-split-hunk').  This is for manually
     editing patches, and only works with the "unified diff format"
     produced by the `-u' or `--unified' options to the `diff' program.
     If you need to split a hunk in the "context diff format" produced
     by the `-c' or `--context' options to `diff', first convert the
     buffer to the unified diff format with `C-c C-u'.

`C-c C-d'
     Convert the entire buffer to the "context diff format"
     (`diff-unified->context').  With a prefix argument, convert only
     the text within the region.

`C-c C-u'
     Convert the entire buffer to unified diff format
     (`diff-context->unified').  With a prefix argument, convert
     unified format to context format.  When the mark is active, convert
     only the text within the region.

`C-c C-w'
     Refine the current hunk so that it disregards changes in whitespace
     (`diff-refine-hunk').

`C-x 4 A'
     Generate a ChangeLog entry, like `C-x 4 a' does (*note Change
     Log::), for each one of the hunks
     (`diff-add-change-log-entries-other-window').  This creates a
     skeleton of the log of changes that you can later fill with the
     actual descriptions of the changes.  `C-x 4 a' itself in Diff mode
     operates on behalf of the current hunk's file, but gets the
     function name from the patch itself.  This is useful for making
     log entries for functions that are deleted by the patch.

`M-x diff-show-trailing-whitespaces RET'
     Highlight trailing whitespace characters, except for those used by
     the patch syntax (*note Useless Whitespace::).


File: emacs,  Node: Misc File Ops,  Next: Compressed Files,  Prev: Diff Mode,  Up: Files

22.11 Miscellaneous File Operations
===================================

Emacs has commands for performing many other operations on files.  All
operate on one file; they do not accept wildcard file names.

   `M-x view-file' allows you to scan or read a file by sequential
screenfuls.  It reads a file name argument using the minibuffer.  After
reading the file into an Emacs buffer, `view-file' displays the
beginning.  You can then type <SPC> to scroll forward one windowful, or
<DEL> to scroll backward.  Various other commands are provided for
moving around in the file, but none for changing it; type `?' while
viewing for a list of them.  They are mostly the same as normal Emacs
cursor motion commands.  To exit from viewing, type `q'.  The commands
for viewing are defined by a special minor mode called View mode.

   A related command, `M-x view-buffer', views a buffer already present
in Emacs.  *Note Misc Buffer::.

   `M-x insert-file' (also `C-x i') inserts a copy of the contents of
the specified file into the current buffer at point, leaving point
unchanged before the contents.  The position after the inserted
contents is added to the mark ring, without activating the mark (*note
Mark Ring::).

   `M-x insert-file-literally' is like `M-x insert-file', except the
file is inserted "literally": it is treated as a sequence of ASCII
characters with no special encoding or conversion, similar to the `M-x
find-file-literally' command (*note Visiting::).

   `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.  *Note Accumulating Text::.  The variable
`write-region-inhibit-fsync' applies to these commands, as well as
saving files; see *note Customize Save::.

   `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 rather than `delete-file'.  *Note
Dired::.

   On some systems, there is a facility called the "Trash" (or "Recycle
Bin"); "deleting" a file normally means moving it into the Trash, and
you can bring the file back from the Trash if you later change your
mind.  By default, Emacs does _not_ use the Trash for file
deletion--when Emacs deletes a file, it is gone forever.  You can tell
Emacs to use the Trash by changing the variable
`delete-by-moving-to-trash' to `t'.  This applies to file deletion via
`M-x delete-file', as well as `M-x delete-directory' (*note
Directories::) and file deletion in Dired (*note Dired Deletion::).  In
addition, you can explicitly move a file into the Trash with the
command `M-x move-file-to-trash'.

   `M-x rename-file' reads two file names OLD and NEW using the
minibuffer, then renames file OLD as NEW.  If the file name 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.

   If the argument NEW is just a directory name, the real new name is
in that directory, with the same non-directory component as OLD.  For
example, `M-x rename-file RET ~/foo RET /tmp RET' renames `~/foo' to
`/tmp/foo'.  The same rule applies to all the remaining commands in
this section.  All of them ask for confirmation when the new file name
already exists, too.

   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 is created as a "hard link" to the existing file.  The new
name must belong on the same file system that the file is on.  On
MS-Windows, this command works only if the file resides in an NTFS file
system.  On MS-DOS, it works by copying the file.

   `M-x copy-file' reads the file OLD and writes a new file named NEW
with the same contents.  `M-x copy-directory' does the same for
directories, by recursive copying all files and subdirectories.

   `M-x make-symbolic-link' reads two file names TARGET and LINKNAME,
then creates a symbolic link named LINKNAME, which points at TARGET.
The effect is that future attempts to open file LINKNAME will refer to
whatever file is named TARGET at the time the opening is done, or will
get an error if the name TARGET is nonexistent at that time.  This
command does not expand the argument TARGET, so that it allows you to
specify a relative name as the target of the link.

   Not all systems support symbolic links; on systems that don't
support them, this command is not defined.

   `M-x set-file-modes' reads a file name followed by a "file mode",
and applies that file mode to the specified file.  File modes, also
called "file permissions", determine whether a file can be read,
written to, or executed, and by whom.  This command reads file modes
using the same symbolic or octal format accepted by the `chmod'
command; for instance, `u+x' means to add execution permission for the
user who owns the file.  It has no effect on operating systems that do
not support file modes.  `chmod' is a convenience alias for this
function.


File: emacs,  Node: Compressed Files,  Next: File Archives,  Prev: Misc File Ops,  Up: Files

22.12 Accessing Compressed Files
================================

Emacs automatically uncompresses compressed files when you visit them,
and automatically recompresses them if you alter them and save them.
Emacs recognizes compressed files by their file names.  File names
ending in `.gz' indicate a file compressed with `gzip'.  Other endings
indicate other compression programs.

   Automatic uncompression and compression apply to all the operations
in which Emacs uses the contents of a file.  This includes visiting it,
saving it, inserting its contents into a buffer, loading it, and byte
compiling it.

   To disable this feature, type the command `M-x
auto-compression-mode'.  You can disable it permanently by customizing
the variable `auto-compression-mode'.


File: emacs,  Node: File Archives,  Next: Remote Files,  Prev: Compressed Files,  Up: Files

22.13 File Archives
===================

A file whose name ends in `.tar' is normally an "archive" made by the
`tar' program.  Emacs views these files in a special mode called Tar
mode which provides a Dired-like list of the contents (*note Dired::).
You can move around through the list just as you would in Dired, and
visit the subfiles contained in the archive.  However, not all Dired
commands are available in Tar mode.

   If Auto Compression mode is enabled (*note Compressed Files::), then
Tar mode is used also for compressed archives--files with extensions
`.tgz', `.tar.Z' and `.tar.gz'.

   The keys `e', `f' and <RET> all extract a component file into its
own buffer.  You can edit it there, and if you save the buffer, the
edited version will replace the version in the Tar buffer.  `v'
extracts a file into a buffer in View mode.  `o' extracts the file and
displays it in another window, so you could edit the file and operate
on the archive simultaneously.  `d' marks a file for deletion when you
later use `x', and `u' unmarks a file, as in Dired.  `C' copies a file
from the archive to disk and `R' renames a file within the archive.
`g' reverts the buffer from the archive on disk.

   The keys `M', `G', and `O' change the file's permission bits, group,
and owner, respectively.

   If your display supports colors and the mouse, moving the mouse
pointer across a file name highlights that file name, indicating that
you can click on it.  Clicking `Mouse-2' on the highlighted file name
extracts the file into a buffer and displays that buffer.

   Saving the Tar buffer writes a new version of the archive to disk
with the changes you made to the components.

   You don't need the `tar' program to use Tar mode--Emacs reads the
archives directly.  However, accessing compressed archives requires the
appropriate uncompression program.

   A separate but similar Archive mode is used for archives produced by
the programs `arc', `jar', `lzh', `zip', `rar', and `zoo', which have
extensions corresponding to the program names.  Archive mode also works
for those `exe' files that are self-extracting executables.

   The key bindings of Archive mode are similar to those in Tar mode,
with the addition of the `m' key which marks a file for subsequent
operations, and `M-<DEL>' which unmarks all the marked files.  Also,
the `a' key toggles the display of detailed file information, for those
archive types where it won't fit in a single line.  Operations such as
renaming a subfile, or changing its mode or owner, are supported only
for some of the archive formats.

   Unlike Tar mode, Archive mode runs the archiving program to unpack
and repack archives.  Details of the program names and their options
can be set in the `Archive' Customize group.  However, you don't need
these programs to look at the archive table of contents, only to
extract or manipulate the subfiles in the archive.


File: emacs,  Node: Remote Files,  Next: Quoted File Names,  Prev: File Archives,  Up: Files

22.14 Remote Files
==================

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

     /HOST:FILENAME
     /USER@HOST:FILENAME
     /USER@HOST#PORT:FILENAME
     /METHOD:USER@HOST:FILENAME
     /METHOD:USER@HOST#PORT:FILENAME

To carry out this request, Emacs uses a remote-login program such as
`ftp', `ssh', `rlogin', or `telnet'.  You can always specify in the
file name which method to use--for example, `/ftp:USER@HOST:FILENAME'
uses FTP, whereas `/ssh:USER@HOST:FILENAME' uses `ssh'.  When you don't
specify a method in the file name, Emacs chooses the method as follows:

  1. If the host name starts with `ftp.' (with dot), then Emacs uses
     FTP.

  2. If the user name is `ftp' or `anonymous', then Emacs uses FTP.

  3. If the variable `tramp-default-method' is set to `ftp', then Emacs
     uses FTP.

  4. If `ssh-agent' is running, then Emacs uses `scp'.

  5. Otherwise, Emacs uses `ssh'.

You can entirely turn off the remote file name feature by setting the
variable `tramp-mode' to `nil'.  You can turn off the feature in
individual cases by quoting the file name with `/:' (*note Quoted File
Names::).

   Remote file access through FTP is handled by the Ange-FTP package,
which is documented in the following.  Remote file access through the
other methods is handled by the Tramp package, which has its own manual.
*Note The Tramp Manual: (tramp)Top.

   When the Ange-FTP package is used, Emacs logs in through FTP using
your user name or the name USER.  It may ask you for a password from
time to time (*note Passwords::); this is used for logging in on HOST.
The form using PORT allows you to access servers running on a
non-default TCP port.

   If you want to disable backups for remote files, set the variable
`ange-ftp-make-backup-files' to `nil'.

   By default, the auto-save files (*note Auto Save Files::) for remote
files are made in the temporary file directory on the local machine.
This is achieved using the variable `auto-save-file-name-transforms'.

   Normally, if you do not specify a user name in a remote file name,
that means to use your own user name.  But if you set the variable
`ange-ftp-default-user' to a string, that string is used instead.

   To visit files accessible by anonymous FTP, you use special user
names `anonymous' or `ftp'.  Passwords for these user names are handled
specially.  The variable `ange-ftp-generate-anonymous-password'
controls what happens: if the value of this variable is a string, then
that string is used as the password; if non-`nil' (the default), then
the value of `user-mail-address' is used; if `nil', then Emacs prompts
you for a password as usual (*note Passwords::).

   Sometimes you may be unable to access files on a remote machine
because a "firewall" in between blocks the connection for security
reasons.  If you can log in on a "gateway" machine from which the
target files _are_ accessible, and whose FTP server supports gatewaying
features, you can still use remote file names; all you have to do is
specify the name of the gateway machine by setting the variable
`ange-ftp-gateway-host', and set `ange-ftp-smart-gateway' to `t'.
Otherwise you may be able to make remote file names work, but the
procedure is complex.  You can read the instructions by typing `M-x
finder-commentary <RET> ange-ftp <RET>'.


File: emacs,  Node: Quoted File Names,  Next: File Name Cache,  Prev: Remote Files,  Up: Files

22.15 Quoted File Names
=======================

You can "quote" an absolute file name to prevent special characters and
syntax in it from having their special effects.  The way to do this is
to add `/:' at the beginning.

   For example, you can quote a local file name which appears remote, to
prevent it from being treated as a remote file name.  Thus, if you have
a directory named `/foo:' and a file named `bar' in it, you can refer
to that file in Emacs as `/:/foo:/bar'.

   `/:' can also prevent `~' from being treated as a special character
for a user's home directory.  For example, `/:/tmp/~hack' refers to a
file whose name is `~hack' in directory `/tmp'.

   Quoting with `/:' is also a way to enter in the minibuffer a file
name that contains `$'.  In order for this to work, the `/:' must be at
the beginning of the minibuffer contents.  (You can also double each
`$'; see *note File Names with $::.)

   You can also quote wildcard characters with `/:', for visiting.  For
example, `/:/tmp/foo*bar' visits the file `/tmp/foo*bar'.

   Another method of getting the same result is to enter
`/tmp/foo[*]bar', which is a wildcard specification that matches only
`/tmp/foo*bar'.  However, in many cases there is no need to quote the
wildcard characters because even unquoted they give the right result.
For example, if the only file name in `/tmp' that starts with `foo' and
ends with `bar' is `foo*bar', then specifying `/tmp/foo*bar' will visit
only `/tmp/foo*bar'.


File: emacs,  Node: File Name Cache,  Next: File Conveniences,  Prev: Quoted File Names,  Up: Files

22.16 File Name Cache
=====================

You can use the "file name cache" to make it easy to locate a file by
name, without having to remember exactly where it is located.  When
typing a file name in the minibuffer, `C-<tab>'
(`file-cache-minibuffer-complete') completes it using the file name
cache.  If you repeat `C-<tab>', that cycles through the possible
completions of what you had originally typed.  (However, note that the
`C-<tab>' character cannot be typed on most text-only terminals.)

   The file name cache does not fill up automatically.  Instead, you
load file names into the cache using these commands:

`M-x file-cache-add-directory <RET> DIRECTORY <RET>'
     Add each file name in DIRECTORY to the file name cache.

`M-x file-cache-add-directory-using-find <RET> DIRECTORY <RET>'
     Add each file name in DIRECTORY and all of its nested
     subdirectories to the file name cache.

`M-x file-cache-add-directory-using-locate <RET> DIRECTORY <RET>'
     Add each file name in DIRECTORY and all of its nested
     subdirectories to the file name cache, using `locate' to find them
     all.

`M-x file-cache-add-directory-list <RET> VARIABLE <RET>'
     Add each file name in each directory listed in VARIABLE to the
     file name cache.  VARIABLE should be a Lisp variable such as
     `load-path' or `exec-path', whose value is a list of directory
     names.

`M-x file-cache-clear-cache <RET>'
     Clear the cache; that is, remove all file names from it.

   The file name cache is not persistent: it is kept and maintained
only for the duration of the Emacs session.  You can view the contents
of the cache with the `file-cache-display' command.


File: emacs,  Node: File Conveniences,  Next: Filesets,  Prev: File Name Cache,  Up: Files

22.17 Convenience Features for Finding Files
============================================

In this section, we introduce some convenient facilities for finding
recently-opened files, reading file names from a buffer, and viewing
image files.

   If you enable Recentf mode, with `M-x recentf-mode', the `File' menu
includes a submenu containing a list of recently opened files.  `M-x
recentf-save-list' saves the current `recent-file-list' to a file, and
`M-x recentf-edit-list' edits it.

   The `M-x ffap' command generalizes `find-file' with more powerful
heuristic defaults (*note FFAP::), often based on the text at point.
Partial Completion mode offers other features extending `find-file',
which can be used with `ffap'.  *Note Completion Options::.

   Visiting image files automatically selects Image mode.  This major
mode allows you to toggle between displaying the file as an image in
the Emacs buffer, and displaying its underlying text representation,
using the command `C-c C-c' (`image-toggle-display').  This works only
when Emacs can display the specific image type.  If the displayed image
is wider or taller than the frame, the usual point motion keys (`C-f',
`C-p', and so forth) cause different parts of the image to be displayed.

   See also the Image-Dired package (*note Image-Dired::) for viewing
images as thumbnails.


File: emacs,  Node: Filesets,  Prev: File Conveniences,  Up: Files

22.18 Filesets
==============

If you regularly edit a certain group of files, you can define them as
a "fileset".  This lets you perform certain operations, such as
visiting, `query-replace', and shell commands on all the files at once.
To make use of filesets, you must first add the expression
`(filesets-init)' to your `.emacs' file (*note Init File::).  This adds
a `Filesets' menu to the menu bar.

   The simplest way to define a fileset is by adding files to it one at
a time.  To add a file to fileset NAME, visit the file and type `M-x
filesets-add-buffer RET NAME RET'.  If there is no fileset NAME, this
creates a new one, which initially creates only the current file.  The
command `M-x filesets-remove-buffer' removes the current file from a
fileset.

   You can also edit the list of filesets directly, with `M-x
filesets-edit' (or by choosing `Edit Filesets' from the `Filesets'
menu).  The editing is performed in a Customize buffer (*note Easy
Customization::).  Filesets need not be a simple list of files--you can
also define filesets using regular expression matching file names.
Some examples of these more complicated filesets are shown in the
Customize buffer.  Remember to select `Save for future sessions' if you
want to use the same filesets in future Emacs sessions.

   You can use the command `M-x filesets-open' to visit all the files
in a fileset, and `M-x filesets-close' to close them.  Use `M-x
filesets-run-cmd' to run a shell command on all the files in a fileset.
These commands are also available from the `Filesets' menu, where each
existing fileset is represented by a submenu.

   Emacs uses the concept of a fileset elsewhere *note Version
Control:: to describe sets of files to be treated as a group for
purposes of version control operations.  Those filesets are unnamed and
do not persist across Emacs sessions.


File: emacs,  Node: Buffers,  Next: Windows,  Prev: Files,  Up: Top

23 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*'.

   Each buffer has a unique name, which can be of any length.  When a
buffer is displayed in a window, its name is shown in the mode line
(*note Mode Line::).  The distinction between upper and lower case
matters in buffer names.  Most buffers are made by visiting files, and
their names are derived from the files' names; however, you can also
create an empty buffer with any name you want.  A newly started Emacs
has a buffer named `*scratch*', which is not associated with any file
and can be used for evaluating Lisp expressions in Emacs (*note Lisp
Interaction::).

   At any time, one and only one buffer is "current".  This is also
called the "selected buffer".  We often say that a command operates on
"the buffer"; this really means that the command operates on the
current buffer (most commands do).  When there is only one Emacs
window, the buffer displayed in that window is current.  When there are
multiple windows present, the buffer displayed in the "selected window"
is current.  *Note Windows::.

   Each buffer records individually what file it is visiting (if any),
whether it is modified, and what major mode and minor modes are in
effect (*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::.

   A buffer's size cannot be larger than some maximum, which is defined
by the largest buffer position representable by the "Emacs integer"
data type.  This is because Emacs tracks buffer positions using that
data type.  For 32-bit machines, the largest buffer size is 512
megabytes.

* 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-onlyness; 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.
* Indirect Buffers::    An indirect buffer shares the text of another buffer.
* Buffer Convenience::  Convenience and customization features for
                          buffer handling.


File: emacs,  Node: Select Buffer,  Next: List Buffers,  Up: Buffers

23.1 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 BUFFER in another window
     (`switch-to-buffer-other-window').

`C-x 5 b BUFFER <RET>'
     Similar, but select BUFFER in a separate frame
     (`switch-to-buffer-other-frame').

`C-x <LEFT>'
     Select the previous buffer in the list of existing buffers.

`C-x <RIGHT>'
     Select the next buffer in the list of existing buffers.

`C-u M-g M-g'
`C-u M-g g'
     Read a number N and move to line N in the most recently selected
     buffer other than the current buffer.

   To select the buffer named BUFNAME, type `C-x b BUFNAME <RET>'.
This runs the command `switch-to-buffer' with argument BUFNAME.  While
entering the buffer name, you can use the usual minibuffer completion
and history commands (*note Minibuffer::).  An empty argument to `C-x
b' specifies the buffer that was current most recently among those not
now displayed in any window.

   If you specify a buffer that does not exist, `C-x b' creates a new,
empty buffer that is not visiting any file, and selects it for editing.
First, however, Emacs might prompt you for confirmation, in case you
entered the wrong buffer name.  Emacs asks for confirmation only if the
last key you typed, before submitting the minibuffer input with <RET>,
was <TAB> (`minibuffer-complete').  This catches a common mistake, in
which one types <RET> before realizing that <TAB> did not complete far
enough to yield the desired buffer name (*note Completion::).  Emacs
asks for confirmation by putting the message `[Confirm]' in the
minibuffer; type <RET> again to confirm and visit the buffer.

   The variable `confirm-nonexistent-file-or-buffer' controls whether
Emacs asks for confirmation before visiting a buffer that did not
previously exist.  The default value, `after-completion', gives the
behavior we have just described.  If the value is `nil', Emacs never
asks for confirmation; for any other non-`nil' value, Emacs always asks
for confirmation.  This variable also affects the `find-file' command
(*note Visiting::).

   One reason to create a new buffer is to use it for making temporary
notes.  If you try to save it, Emacs asks for the file name to use.
The default value of the variable `major-mode' determines the new
buffer's major mode; the default value is Fundamental mode.  *Note
Major Modes::.

   For conveniently switching between a few buffers, use the commands
`C-x <LEFT>' and `C-x <RIGHT>'.  `C-x <RIGHT>' (`previous-buffer')
selects the previous buffer (following the order of most recent
selection in the current frame), while `C-x <LEFT>' (`next-buffer')
moves through buffers in the reverse direction.

   To select a buffer in a window other than the current one, type `C-x
4 b' (`switch-to-buffer-other-window').  This prompts for a buffer name
using the minibuffer, displays that buffer in another window, and
selects that window.  By default, if displaying the buffer causes two
vertically adjacent windows to be displayed, the heights of those
windows are evened out; to countermand that and preserve the window
configuration, set the variable `even-window-heights' to `nil'.

   Similarly, `C-x 5 b' (`switch-to-buffer-other-frame') prompts for a
buffer name, displays that buffer in another frame, and selects that
frame.

   In addition, `C-x C-f', and any other command for visiting a file,
can also be used to switch to an existing file-visiting buffer.  *Note
Visiting::.

   You can control how certain buffers are handled by these commands by
customizing the variables `special-display-buffer-names',
`special-display-regexps', `same-window-buffer-names', and
`same-window-regexps'.  See *note Force Same Window::, and *note
Special Buffer Frames::, for more about these variables.  In addition,
if the value of `display-buffer-reuse-frames' is non-`nil', and the
buffer you want to switch to is already displayed in some frame, Emacs
will just raise that frame.

   `C-u M-g M-g', that is `goto-line' with a plain prefix argument,
reads a number N using the minibuffer, selects the most recently
selected buffer other than the current buffer in another window, and
then moves point to the beginning of line number N in that buffer.
This is mainly useful in a buffer that refers to line numbers in
another buffer: if point is on or just after a number, `goto-line' uses
that number as the default for N.  Note that prefix arguments other
than just `C-u' behave differently.  `C-u 4 M-g M-g' goes to line 4 in
the _current_ buffer, without reading a number from the minibuffer.
(Remember that `M-g M-g' without prefix argument reads a number N and
then moves to line number N in the current buffer.  *Note Moving
Point::.)

   Emacs uses buffer names that start with a space for internal
purposes.  It treats these buffers specially in minor ways--for
example, by default they do not record undo information.  It is best to
avoid using such buffer names yourself.


File: emacs,  Node: List Buffers,  Next: Misc Buffer,  Prev: Select Buffer,  Up: Buffers

23.2 Listing Existing Buffers
=============================

`C-x C-b'
     List the existing buffers (`list-buffers').

   To display a list of existing buffers, type `C-x C-b'.  Each line in
the list shows one buffer's name, major mode and visited file.  The
buffers are listed in the order that they were current; the buffers
that were current most recently come first.

   `.' in the first field of a line indicates that the buffer is
current.  `%' indicates a read-only buffer.  `*' indicates that the
buffer is "modified."  If several buffers are modified, it may be time
to save some with `C-x s' (*note Save Commands::).  Here is an example
of a buffer list:

     CRM Buffer                Size  Mode              File
     . * .emacs                3294  Emacs-Lisp        ~/.emacs
      %  *Help*                 101  Help
         search.c             86055  C                 ~/cvs/emacs/src/search.c
      %  src                  20959  Dired by name     ~/cvs/emacs/src/
       * *mail*                  42  Mail
      %  HELLO                 1607  Fundamental       ~/cvs/emacs/etc/HELLO
      %  NEWS                481184  Outline           ~/cvs/emacs/etc/NEWS
         *scratch*              191  Lisp Interaction
       * *Messages*            1554  Fundamental

The buffer `*Help*' was made by a help request (*note Help::); it is
not visiting any file.  The buffer `src' was made by Dired on the
directory `~/cvs/emacs/src/'.  You can list only buffers that are
visiting files by giving the command a prefix argument, as in `C-u C-x
C-b'.

   `list-buffers' omits buffers whose names begin with a space, unless
they visit files: such buffers are used internally by Emacs.


File: emacs,  Node: Misc Buffer,  Next: Kill Buffer,  Prev: List Buffers,  Up: Buffers

23.3 Miscellaneous Buffer Operations
====================================

`C-x C-q'
     Toggle read-only status of buffer (`toggle-read-only').

`M-x rename-buffer <RET> NAME <RET>'
     Change the name of the current buffer.

`M-x rename-uniquely'
     Rename the current buffer by adding `<NUMBER>' to the end.

`M-x view-buffer <RET> BUFFER <RET>'
     Scroll through buffer BUFFER.

   A buffer can be "read-only", which means that commands to change its
contents are not allowed.  The mode line indicates read-only buffers
with `%%' or `%*' near the left margin.  Read-only buffers are usually
made by subsystems such as Dired and Rmail that have special commands
to operate on the text; also by visiting a file whose access control
says 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'.  If you have
files under version control, you may find it convenient to bind `C-x
C-q' to `vc-toggle-read-only' instead.  This will guard you against an
operation that will confuse most modern version-conmtrol systems. *Note
Version Control::.

   `M-x rename-buffer' changes the name of the current buffer.  You
specify the new name as a minibuffer argument; there is no default.  If
you specify a name that is in use for some other buffer, an error
happens and no renaming is done.

   `M-x rename-uniquely' renames the current buffer to a similar name
with a numeric suffix added to make it both different and unique.  This
command does not need an argument.  It is useful for creating multiple
shell buffers: if you rename the `*shell*' buffer, then do `M-x shell'
again, it makes a new shell buffer named `*shell*'; meanwhile, the old
shell buffer continues to exist under its new name.  This method is
also good for mail buffers, compilation buffers, and most Emacs
features that create special buffers with particular names.  (With some
of these features, such as `M-x compile', `M-x grep' an `M-x info', you
need to switch to some other buffer before using the command, in order
for it to make a different buffer.)

   `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 with `q', that
switches back to the buffer (and the position) which was previously
displayed in the window.  Alternatively, if you exit View mode with
`e', the buffer and the value of point that resulted from your perusal
remain in effect.

   The commands `M-x append-to-buffer' and `M-x insert-buffer' can be
used to copy text from one buffer to another.  *Note Accumulating
Text::.


File: emacs,  Node: Kill Buffer,  Next: Several Buffers,  Prev: Misc Buffer,  Up: Buffers

23.4 Killing Buffers
====================

If you continue an Emacs session for a while, you may accumulate a
large number of buffers.  You may then find it convenient to "kill" the
buffers you no longer need.  On most operating systems, killing a
buffer releases its space back to the operating system so that other
programs can use it.  Here are some commands for killing buffers:

`C-x k BUFNAME <RET>'
     Kill buffer BUFNAME (`kill-buffer').

`M-x kill-some-buffers'
     Offer to kill each buffer, one by one.

`M-x kill-matching-buffers'
     Offer to kill all buffers matching a regular expression.

   `C-x k' (`kill-buffer') kills one buffer, whose name you specify in
the minibuffer.  The default, used if you type just <RET> in the
minibuffer, is to kill the current buffer.  If you kill the current
buffer, another buffer becomes current: one that was current in the
recent past but is not displayed in any window now.  If you ask to kill
a file-visiting buffer that is modified, then you must confirm with
`yes' before the buffer is killed.

   The command `M-x kill-some-buffers' asks about each buffer, one by
one.  An answer of `y' means to kill the buffer, just like
`kill-buffer'.  This command ignores buffers whose names begin with a
space, which are used internally by Emacs.

   The command `M-x kill-matching-buffers' prompts for a regular
expression and kills all buffers whose names match that expression.
*Note Regexps::.  Like `kill-some-buffers', it asks for confirmation
before each kill.  This command normally ignores buffers whose names
begin with a space, which are used internally by Emacs.  To kill
internal buffers as well, call `kill-matching-buffers' with a prefix
argument.

   The buffer menu feature is also convenient for killing various
buffers.  *Note Several Buffers::.

   If you want to do something special every time a buffer is killed,
you can add hook functions to the hook `kill-buffer-hook' (*note
Hooks::).

   If you run one Emacs session for a period of days, as many people do,
it can fill up with buffers that you used several days ago.  The command
`M-x clean-buffer-list' is a convenient way to purge them; it kills all
the unmodified buffers that you have not used for a long time.  An
ordinary buffer is killed if it has not been displayed for three days;
however, you can specify certain buffers that should never be killed
automatically, and others that should be killed if they have been unused
for a mere hour.

   You can also have this buffer purging done for you, every day at
midnight, by enabling Midnight mode.  Midnight mode operates each day
at midnight; at that time, it runs `clean-buffer-list', or whichever
functions you have placed in the normal hook `midnight-hook' (*note
Hooks::).  To enable Midnight mode, use the Customization buffer to set
the variable `midnight-mode' to `t'.  *Note Easy Customization::.


File: emacs,  Node: Several Buffers,  Next: Indirect Buffers,  Prev: Kill Buffer,  Up: Buffers

23.5 Operating on Several Buffers
=================================

`M-x buffer-menu'
     Begin editing a buffer listing all Emacs buffers.

`M-x buffer-menu-other-window.'
     Similar, but do it in another window.

   The "buffer menu" opened by `C-x C-b' (*note List Buffers::) does
not merely list buffers.  It also allows you to perform various
operations on buffers, through an interface similar to Dired (*note
Dired::).  You can save buffers, kill them (here called "deleting"
them, for consistency with Dired), or display them.

   To use the buffer menu, type `C-x C-b' and switch to the window
displaying the `*Buffer List*' buffer.  You can also type `M-x
buffer-menu' to open the buffer menu in the selected window.
Alternatively, the command `M-x buffer-menu-other-window' opens the
buffer menu in another window, and selects that window.

   The buffer menu is a read-only buffer, and can be changed only
through the special commands described in this section.  The usual
Emacs cursor motion commands can be used in this buffer.  The following
commands apply to the buffer described on the current line:

`d'
     Request to delete (kill) the buffer, then move down.  The request
     shows as a `D' on the line, before the buffer name.  Requested
     deletions take place when you type the `x' command.

`C-d'
     Like `d' but move up afterwards instead of down.

`s'
     Request to save the buffer.  The request shows as an `S' on the
     line.  Requested saves take place when you type the `x' command.
     You may request both saving and deletion for the same buffer.

`x'
     Perform previously requested deletions and saves.

`u'
     Remove any request made for the current line, and move down.

`<DEL>'
     Move to previous line and remove any request made for that line.

   The `d', `C-d', `s' and `u' commands to add or remove flags also
move down (or up) one line.  They accept a numeric argument as a repeat
count.

   These commands operate immediately on the buffer listed on the
current line:

`~'
     Mark the buffer "unmodified."  The command `~' does this
     immediately when you type it.

`%'
     Toggle the buffer's read-only flag.  The command `%' does this
     immediately when you type it.

`t'
     Visit the buffer as a tags table.  *Note Select Tags Table::.

   There are also commands to select another buffer or buffers:

`q'
     Quit the buffer menu--immediately display the most recent formerly
     visible buffer in its place.

`<RET>'
`f'
     Immediately select this line's buffer in place of the `*Buffer
     List*' buffer.

`o'
     Immediately select this line's buffer in another window as if by
     `C-x 4 b', leaving `*Buffer List*' visible.

`C-o'
     Immediately display this line's buffer in another window, but don't
     select the window.

`1'
     Immediately select this line's buffer in a full-screen window.

`2'
     Immediately set up two windows, with this line's buffer selected in
     one, and the previously current buffer (aside from the buffer
     `*Buffer List*') displayed in the other.

`b'
     Bury the buffer listed on this line.

`m'
     Mark this line's buffer to be displayed in another window if you
     exit with the `v' command.  The request shows as a `>' at the
     beginning of the line.  (A single buffer may not have both a delete
     request and a display request.)

`v'
     Immediately select this line's buffer, and also display in other
     windows any buffers previously marked with the `m' command.  If
     you have not marked any buffers, this command is equivalent to `1'.

   There is also a command that affects the entire buffer list:

`T'
     Delete, or reinsert, lines for non-file buffers.  This command
     toggles the inclusion of such buffers in the buffer list.

   What `buffer-menu' actually does is create and switch to a suitable
buffer, and turn on Buffer Menu mode in it.  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 List*' buffer later, to perform the operations
already requested, or you can kill it, or pay no further attention to
it.

   Normally, the buffer `*Buffer List*' is not updated automatically
when buffers are created and killed; its contents are just text.  If
you have created, deleted or renamed buffers, the way to update
`*Buffer List*' to show what you have done is to type `g'
(`revert-buffer').  You can make this happen regularly every
`auto-revert-interval' seconds if you enable Auto Revert mode in this
buffer, as long as it is not marked modified.  Global Auto Revert mode
applies to the `*Buffer List*' buffer only if
`global-auto-revert-non-file-buffers' is non-`nil'.  *Note
global-auto-revert-non-file-buffers: Autorevert, for details.


File: emacs,  Node: Indirect Buffers,  Next: Buffer Convenience,  Prev: Several Buffers,  Up: Buffers

23.6 Indirect Buffers
=====================

An "indirect buffer" shares the text of some other buffer, which is
called the "base buffer" of the indirect buffer.  In some ways it is
the analogue, for buffers, of a symbolic link between files.

`M-x make-indirect-buffer <RET> BASE-BUFFER <RET> INDIRECT-NAME <RET>'
     Create an indirect buffer named INDIRECT-NAME whose base buffer is
     BASE-BUFFER.  

`M-x clone-indirect-buffer <RET>'
     Create an indirect buffer that is a twin copy of the current
     buffer.

`C-x 4 c'
     Create an indirect buffer that is a twin copy of the current
     buffer, and select it in another window
     (`clone-indirect-buffer-other-window').

   The text of the indirect buffer is always identical to the text of
its base buffer; changes made by editing either one are visible
immediately in the other.  But in all other respects, the indirect
buffer and its base buffer are completely separate.  They can have
different names, different values of point, different narrowing,
different markers, different major modes, and different local variables.

   An indirect buffer cannot visit a file, but its base buffer can.  If
you try to save the indirect buffer, that actually works by saving the
base buffer.  Killing the base buffer effectively kills the indirect
buffer, but killing an indirect buffer has no effect on its base buffer.

   One way to use indirect buffers is to display multiple views of an
outline.  *Note Outline Views::.

   A quick and handy way to make an indirect buffer is with the command
`M-x clone-indirect-buffer'.  It creates and selects an indirect buffer
whose base buffer is the current buffer.  With a numeric argument, it
prompts for the name of the indirect buffer; otherwise it uses the name
of the current buffer, with a `<N>' suffix added.  `C-x 4 c'
(`clone-indirect-buffer-other-window') works like `M-x
clone-indirect-buffer', but it selects the new buffer in another
window.  These functions run the hook `clone-indirect-buffer-hook'
after creating the indirect buffer.

   The more general way to make an indirect buffer is with the command
`M-x make-indirect-buffer'.  It creates an indirect buffer from buffer
BASE-BUFFER, under the name INDIRECT-NAME.  It prompts for both
BASE-BUFFER and INDIRECT-NAME using the minibuffer.


File: emacs,  Node: Buffer Convenience,  Prev: Indirect Buffers,  Up: Buffers

23.7 Convenience Features and Customization of Buffer Handling
==============================================================

This section describes several modes and features that make it more
convenient to switch between buffers.

* Menu:

* Uniquify::               Making buffer names unique with directory parts.
* Iswitchb::               Switching between buffers with substrings.
* Buffer Menus::           Configurable buffer menu.


File: emacs,  Node: Uniquify,  Next: Iswitchb,  Up: Buffer Convenience

23.7.1 Making Buffer Names Unique
---------------------------------

When several buffers visit identically-named files, Emacs must give the
buffers distinct names.  The usual method for making buffer names
unique adds `<2>', `<3>', etc. to the end of the buffer names (all but
one of them).

   Other methods work by adding parts of each file's directory to the
buffer name.  To select one, load the library `uniquify' (e.g.  using
`(require 'uniquify)'), and customize the variable
`uniquify-buffer-name-style' (*note Easy Customization::).

   To begin with, the `forward' naming method includes part of the
file's directory name at the beginning of the buffer name; using this
method, buffers visiting the files `/u/rms/tmp/Makefile' and
`/usr/projects/zaphod/Makefile' would be named `tmp/Makefile' and
`zaphod/Makefile', respectively (instead of `Makefile' and
`Makefile<2>').

   In contrast, the `post-forward' naming method would call the buffers
`Makefile|tmp' and `Makefile|zaphod', and the `reverse' naming method
would call them `Makefile\tmp' and `Makefile\zaphod'.  The nontrivial
difference between `post-forward' and `reverse' occurs when just one
directory name is not enough to distinguish two files; then `reverse'
puts the directory names in reverse order, so that `/top/middle/file'
becomes `file\middle\top', while `post-forward' puts them in forward
order after the file name, as in `file|top/middle'.

   Which rule to follow for putting the directory names in the buffer
name is not very important if you are going to _look_ at the buffer
names before you type one.  But as an experienced user, if you know the
rule, you won't have to look.  And then you may find that one rule or
another is easier for you to remember and apply quickly.


File: emacs,  Node: Iswitchb,  Next: Buffer Menus,  Prev: Uniquify,  Up: Buffer Convenience

23.7.2 Switching Between Buffers using Substrings
-------------------------------------------------

Iswitchb global minor mode provides convenient switching between
buffers using substrings of their names.  It replaces the normal
definitions of `C-x b', `C-x 4 b', `C-x 5 b', and `C-x 4 C-o' with
alternative commands that are somewhat "smarter."

   When one of these commands prompts you for a buffer name, you can
type in just a substring of the name you want to choose.  As you enter
the substring, Iswitchb mode continuously displays a list of buffers
that match the substring you have typed.

   At any time, you can type <RET> to select the first buffer in the
list.  So the way to select a particular buffer is to make it the first
in the list.  There are two ways to do this.  You can type more of the
buffer name and thus narrow down the list, excluding unwanted buffers
above the desired one.  Alternatively, you can use `C-s' and `C-r' to
rotate the list until the desired buffer is first.

   <TAB> while entering the buffer name performs completion on the
string you have entered, based on the displayed list of buffers.

   To enable Iswitchb mode, type `M-x iswitchb-mode', or customize the
variable `iswitchb-mode' to `t' (*note Easy Customization::).


File: emacs,  Node: Buffer Menus,  Prev: Iswitchb,  Up: Buffer Convenience

23.7.3 Customizing Buffer Menus
-------------------------------

`M-x bs-show'
     Make a list of buffers similarly to `M-x list-buffers' but
     customizable.

   `M-x bs-show' pops up a buffer list similar to the one normally
displayed by `C-x C-b' but which you can customize.  If you prefer this
to the usual buffer list, you can bind this command to `C-x C-b'.  To
customize this buffer list, use the `bs' Custom group (*note Easy
Customization::).

   MSB global minor mode ("MSB" stands for "mouse select buffer")
provides a different and customizable mouse buffer menu which you may
prefer.  It replaces the bindings of `mouse-buffer-menu', normally on
`C-Down-Mouse-1', and the menu bar buffer menu.  You can customize the
menu in the `msb' Custom group.


File: emacs,  Node: Windows,  Next: Frames,  Prev: Buffers,  Up: Top

24 Multiple Windows
*******************

Emacs can split a frame into two or many windows.  Multiple windows can
display parts of different buffers, or different parts of one buffer.
Multiple frames always imply multiple windows, because each frame has
its own set of windows.  Each window belongs to one and only one frame.

* Menu:

* Basic Window::        Introduction to Emacs windows.
* Split Window::        New windows are made by splitting existing windows.
* Other Window::        Moving to another window or doing something to it.
* Pop Up Window::       Finding a file or buffer in another window.
* Force Same Window::   Forcing certain buffers to appear in the selected
                          window rather than in another window.
* Change Window::       Deleting windows and changing their sizes.
* Window Convenience::  Convenience functions for window handling.


File: emacs,  Node: Basic Window,  Next: Split Window,  Up: Windows

24.1 Concepts of Emacs Windows
==============================

Each Emacs window displays one Emacs buffer at any time.  A single
buffer may appear in more than one window; if it does, any changes in
its text are displayed in all the windows where it appears.  But these
windows can show different parts of the buffer, because each window has
its own value of point.

   At any time, one Emacs window is the "selected window"; the buffer
this window is displaying is the current buffer.  The terminal's cursor
shows the location of point in this window.  Each other window has a
location of point as well.  On text-only terminals, there is no way to
show where those locations are, since the terminal has only one cursor.
On a graphical display, the location of point in a non-selected window
is indicated by a hollow box; the cursor in the selected window is
blinking or solid.

   Commands to move point affect the value of point for the selected
Emacs window only.  They do not change the value of point in other Emacs
windows, even those showing the same buffer.  The same is true for
commands such as `C-x b' to switch buffers in the selected window; they
do not affect other windows at all.  However, there are other commands
such as `C-x 4 b' that select a different window and switch buffers in
it.  Also, all commands that display information in a window, including
(for example) `C-h f' (`describe-function') and `C-x C-b'
(`list-buffers'), work by switching buffers in a nonselected window
without affecting the selected window.

   When multiple windows show the same buffer, they can have different
regions, because they can have different values of point.  However,
they all have the same value for the mark, because each buffer has only
one mark position.

   Each window has its own mode line, which displays the buffer name,
modification status and major and minor modes of the buffer that is
displayed in the window.  The selected window's mode line appears in a
different color.  *Note Mode Line::, for full details on the mode line.


File: emacs,  Node: Split Window,  Next: Other Window,  Prev: Basic Window,  Up: Windows

24.2 Splitting Windows
======================

`C-x 2'
     Split the selected window into two windows, one above the other
     (`split-window-vertically').

`C-x 3'
     Split the selected window into two windows positioned side by side
     (`split-window-horizontally').

`C-Mouse-2'
     In the mode line or scroll bar of a window, split that window.

   The command `C-x 2' (`split-window-vertically') breaks the selected
window into two windows, one above the other.  Both windows start out
displaying the same buffer, with the same value of point.  By default
the two windows each get half the height of the window that was split; a
numeric argument specifies how many lines to give to the top window.

   `C-x 3' (`split-window-horizontally') breaks the selected window
into two side-by-side windows.  A numeric argument specifies how many
columns to give the one on the left.  If you are not using scrollbars,
a vertical line separates the two windows.  You can customize its color
with the face `vertical-border'.  Windows that are not the full width
of the screen have mode lines, but they are truncated.  On terminals
where Emacs does not support highlighting, truncated mode lines
sometimes do not appear in inverse video.

   You can split a window horizontally or vertically by clicking
`C-Mouse-2' in the mode line or the scroll bar.  The line of splitting
goes through the place where you click: if you click on the mode line,
the new scroll bar goes above the spot; if you click in the scroll bar,
the mode line of the split window is side by side with your click.

   When a window occupies less than the full width of the frame, it may
become too narrow for most of the text lines in its buffer.  If most of
its lines are continued (*note Continuation Lines::), the buffer may
become difficult to read.  Therefore, Emacs automatically truncates
lines if the window width becomes narrower than 50 columns.  This
truncation occurs regardless of the value of the variable
`truncate-lines' (*note Line Truncation::); it is instead controlled by
the variable `truncate-partial-width-windows'.  If the value of
`truncate-partial-width-windows' is a positive integer (the default is
50), that specifies the minimum width for a partial-width window before
automatic line truncation occurs; if the value is `nil', automatic line
truncation is disabled; and for any other non-`nil' value, Emacs
truncates lines in every partial-width window regardless of its width.

   Horizontal scrolling is often used in side-by-side windows.  *Note
Horizontal Scrolling::.

   If `split-window-keep-point' is non-`nil', the default, both of the
windows resulting from `C-x 2' inherit the value of point from the
window that was split.  This means that scrolling is inevitable.  If
this variable is `nil', then `C-x 2' tries to avoid scrolling the text
currently visible on the screen, by putting point in each window at a
position already visible in the window.  It also selects whichever
window contains the screen line that the cursor was previously on.
Some users prefer that mode on slow terminals.


File: emacs,  Node: Other Window,  Next: Pop Up Window,  Prev: Split Window,  Up: Windows

24.3 Using Other Windows
========================

`C-x o'
     Select another window (`other-window').  That is `o', not zero.

`C-M-v'
     Scroll the next window (`scroll-other-window').

`M-x compare-windows'
     Find next place where the text in the selected window does not
     match the text in the next window.

`Mouse-1'
     `Mouse-1', in a window's mode line, selects that window but does
     not move point in it (`mouse-select-window').

   To select a different window, click with `Mouse-1' on its mode line.
With the keyboard, you can switch windows by typing `C-x o'
(`other-window').  That is an `o', for "other," not a zero.  When there
are more than two windows, this command moves through all the windows
in a cyclic order, generally top to bottom and left to right.  After
the rightmost and bottommost window, it goes back to the one at the
upper left corner.  A numeric argument means to move several steps in
the cyclic order of windows.  A negative argument moves around the
cycle in the opposite order.  When the minibuffer is active, the
minibuffer is the last window in the cycle; you can switch from the
minibuffer window to one of the other windows, and later switch back and
finish supplying the minibuffer argument that is requested.  *Note
Minibuffer Edit::.

   The usual scrolling commands (*note Display::) apply to the selected
window only, but there is one command to scroll the next window.
`C-M-v' (`scroll-other-window') scrolls the window that `C-x o' would
select.  It takes arguments, positive and negative, like `C-v'.  (In
the minibuffer, `C-M-v' scrolls the window that contains the minibuffer
help display, if any, rather than the next window in the standard
cyclic order.)

   The command `M-x compare-windows' lets you compare two files or
buffers visible in two windows, by moving through them to the next
mismatch.  *Note Comparing Files::, for details.

   If you set `mouse-autoselect-window' to a non-`nil' value, moving
the mouse into a different window selects that window.  This feature is
off by default.


File: emacs,  Node: Pop Up Window,  Next: Force Same Window,  Prev: Other Window,  Up: Windows

24.4 Displaying in Another Window
=================================

`C-x 4' is a prefix key for commands that select another window
(splitting the window if there is only one) and select a buffer in that
window.  Different `C-x 4' commands have different ways of finding the
buffer to select.

`C-x 4 b BUFNAME <RET>'
     Select buffer BUFNAME in another window.  This runs
     `switch-to-buffer-other-window'.

`C-x 4 C-o BUFNAME <RET>'
     Display buffer BUFNAME in another window, but don't select that
     buffer or that window.  This runs `display-buffer'.

`C-x 4 f FILENAME <RET>'
     Visit file FILENAME and select its buffer in another window.  This
     runs `find-file-other-window'.  *Note Visiting::.

`C-x 4 d DIRECTORY <RET>'
     Select a Dired buffer for directory DIRECTORY in another window.
     This runs `dired-other-window'.  *Note Dired::.

`C-x 4 m'
     Start composing a mail message in another window.  This runs
     `mail-other-window'; its same-window analogue is `C-x m' (*note
     Sending Mail::).

`C-x 4 .'
     Find a tag in the current tags table, in another window.  This runs
     `find-tag-other-window', the multiple-window variant of `M-.'
     (*note Tags::).

`C-x 4 r FILENAME <RET>'
     Visit file FILENAME read-only, and select its buffer in another
     window.  This runs `find-file-read-only-other-window'.  *Note
     Visiting::.

   By default, these commands split the window vertically when there is
only one.  You can customize the variables `split-height-threshold' and
`split-width-threshold' to split the window horizontally instead.


File: emacs,  Node: Force Same Window,  Next: Change Window,  Prev: Pop Up Window,  Up: Windows

24.5 Forcing Display in the Same Window
=======================================

Certain Emacs commands switch to a specific buffer with special
contents.  For example, `M-x shell' switches to a buffer named
`*shell*'.  By convention, all these commands are written to pop up the
buffer in a separate window.  But you can specify that certain of these
buffers should appear in the selected window.

   If you add a buffer name to the list `same-window-buffer-names', the
effect is that such commands display that particular buffer by
switching to it in the selected window.  For example, if you add the
element `"*grep*"' to the list, the `grep' command will display its
output buffer in the selected window.

   The default value of `same-window-buffer-names' is not `nil': it
specifies buffer names `*info*', `*mail*' and `*shell*' (as well as
others used by more obscure Emacs packages).  This is why `M-x shell'
normally switches to the `*shell*' buffer in the selected window.  If
you delete this element from the value of `same-window-buffer-names',
the behavior of `M-x shell' will change--it will pop up the buffer in
another window instead.

   You can specify these buffers more generally with the variable
`same-window-regexps'.  Set it to a list of regular expressions; then
any buffer whose name matches one of those regular expressions is
displayed by switching to it in the selected window.  (Once again, this
applies only to buffers that normally get displayed for you in a
separate window.)  The default value of this variable specifies Telnet
and rlogin buffers.

   An analogous feature lets you specify buffers which should be
displayed in their own individual frames.  *Note Special Buffer
Frames::.


File: emacs,  Node: Change Window,  Next: Window Convenience,  Prev: Force Same Window,  Up: Windows

24.6 Deleting and Rearranging Windows
=====================================

`C-x 0'
     Delete the selected window (`delete-window').  The last character
     in this key sequence is a zero.

`C-x 1'
     Delete all windows in the selected frame except the selected window
     (`delete-other-windows').

`C-x 4 0'
     Delete the selected window and kill the buffer that was showing in
     it (`kill-buffer-and-window').  The last character in this key
     sequence is a zero.

`C-x ^'
     Make selected window taller (`enlarge-window').

`C-x }'
     Make selected window wider (`enlarge-window-horizontally').

`C-x {'
     Make selected window narrower (`shrink-window-horizontally').

`C-x -'
     Shrink this window if its buffer doesn't need so many lines
     (`shrink-window-if-larger-than-buffer').

`C-x +'
     Make all windows the same height (`balance-windows').

   To delete a window, type `C-x 0' (`delete-window').  (That is a
zero.)  The space occupied by the deleted window is given to an
adjacent window (but not the minibuffer window, even if that is active
at the time).  Once a window is deleted, its attributes are forgotten;
only restoring a window configuration can bring it back.  Deleting the
window has no effect on the buffer it used to display; the buffer
continues to exist, and you can select it in any window with `C-x b'.

   `C-x 4 0' (`kill-buffer-and-window') is a stronger command than `C-x
0'; it kills the current buffer and then deletes the selected window.

   `C-x 1' (`delete-other-windows') is more powerful in a different
way; it deletes all the windows except the selected one (and the
minibuffer); the selected window expands to use the whole frame except
for the echo area.

   To readjust the division of space among vertically adjacent windows,
use `C-x ^' (`enlarge-window').  It makes the currently selected window
one line bigger, or as many lines as is specified with a numeric
argument.  With a negative argument, it makes the selected window
smaller.  `C-x }' (`enlarge-window-horizontally') makes the selected
window wider by the specified number of columns.  `C-x {'
(`shrink-window-horizontally') makes the selected window narrower by
the specified number of columns.

   When you make a window bigger, the space comes from its peers.  If
this makes any window too small, it is deleted and its space is given
to an adjacent window.  The minimum size is specified by the variables
`window-min-height' and `window-min-width'.

   `C-x -' (`shrink-window-if-larger-than-buffer') reduces the height
of the selected window, if it is taller than necessary to show the
whole text of the buffer it is displaying.  It gives the extra lines to
other windows in the frame.

   You can also use `C-x +' (`balance-windows') to even out the heights
of all the windows in the selected frame.

   Mouse clicks on the mode line provide another way to change window
heights and to delete windows.  *Note Mode Line Mouse::.


File: emacs,  Node: Window Convenience,  Prev: Change Window,  Up: Windows

24.7 Window Handling Convenience Features and Customization
===========================================================

`M-x winner-mode' is a global minor mode that records the changes in
the window configuration (i.e. how the frames are partitioned into
windows), so that you can "undo" them.  To undo, use `C-c left'
(`winner-undo').  If you change your mind while undoing, you can redo
the changes you had undone using `C-c right' (`M-x winner-redo').
Another way to enable Winner mode is by customizing the variable
`winner-mode'.

   The Windmove commands move directionally between neighboring windows
in a frame.  `M-x windmove-right' selects the window immediately to the
right of the currently selected one, and similarly for the "left," "up,"
and "down" counterparts.  `M-x windmove-default-keybindings' binds
these commands to `S-right' etc.  (Not all terminals support shifted
arrow keys, however.)

   Follow minor mode (`M-x follow-mode') synchronizes several windows
on the same buffer so that they always display adjacent sections of
that buffer.  *Note Follow Mode::.

   `M-x scroll-all-mode' provides commands to scroll all visible
windows together.  You can also turn it on by customizing the variable
`scroll-all-mode'.  The commands provided are `M-x
scroll-all-scroll-down-all', `M-x scroll-all-page-down-all' and their
corresponding "up" equivalents.  To make this mode useful, you should
bind these commands to appropriate keys.


File: emacs,  Node: Frames,  Next: International,  Prev: Windows,  Up: Top

25 Frames and Graphical Displays
********************************

When using a graphical display, you can create multiple system-level
"windows" in a single Emacs session.  We refer to these system-level
windows as "frames".  A frame initially contains a single Emacs window;
however, you can subdivide this Emacs window into smaller windows, all
fitting into the same frame.  Each frame normally contains its own echo
area and minibuffer.

   To avoid confusion, we reserve the word "window" for the
subdivisions that Emacs implements, and never use it to refer to a
frame.

   Any editing you do in one frame affects the other frames.  For
instance, if you put text in the kill ring in one frame, you can yank
it in another frame.  If you exit Emacs through `C-x C-c' in one frame,
it terminates all the frames.  To delete just one frame, use `C-x 5 0'
(that is zero, not `o').

   Emacs compiled for MS-DOS emulates some windowing functionality, so
that you can use many of the features described in this chapter.  *Note
MS-DOS Mouse::.

* Menu:

* Cut and Paste::       Mouse commands for cut and paste.
* Mouse References::    Using the mouse to select an item from a list.
* Menu Mouse Clicks::   Mouse clicks that bring up menus.
* Mode Line Mouse::     Mouse clicks on the mode line.
* Creating Frames::     Creating additional Emacs frames with various contents.
* Frame Commands::      Iconifying, deleting, and switching frames.
* Fonts::               Changing the frame font.
* Speedbar::            How to make and use a speedbar frame.
* Multiple Displays::   How one Emacs job can talk to several displays.
* Special Buffer Frames::  You can make certain buffers have their own frames.
* Frame Parameters::    Changing the colors and other modes of frames.
* Scroll Bars::         How to enable and disable scroll bars; how to use them.
* Wheeled Mice::        Using mouse wheels for scrolling.
* Drag and Drop::       Using drag and drop to open files and insert text.
* Menu Bars::           Enabling and disabling the menu bar.
* Tool Bars::           Enabling and disabling the tool bar.
* Dialog Boxes::        Controlling use of dialog boxes.
* Tooltips::            Displaying information at the current mouse position.
* Mouse Avoidance::     Preventing the mouse pointer from obscuring text.
* Non-Window Terminals::  Multiple frames on terminals that show only one.
* Text-Only Mouse::     Using the mouse in text-only terminals.


File: emacs,  Node: Cut and Paste,  Next: Mouse References,  Up: Frames

25.1 Cutting and Pasting on Graphical Displays
==============================================

This section describes commands for selecting a region, cutting, and
pasting using the mouse.

* Menu:

* Mouse Commands::      Moving, cutting, and pasting, with the mouse.
* Word and Line Mouse:: Mouse commands for selecting whole words or lines.
* Cut/Paste Other App:: Transfering text between Emacs and other apps.
* Secondary Selection:: Cutting without altering point and mark.
* Clipboard::           Using the clipboard for selections.


File: emacs,  Node: Mouse Commands,  Next: Word and Line Mouse,  Up: Cut and Paste

25.1.1 Mouse Commands for Editing
---------------------------------

`Mouse-1'
     Move point to where you click (`mouse-set-point').

`Drag-Mouse-1'
     Activate the region around the text selected by dragging, and copy
     it to the kill ring (`mouse-set-region').

`Mouse-2'
     Yank the last killed text at the click position
     (`mouse-yank-at-click').

`Mouse-3'
     If the region is active, move the nearer end of the region to the
     click position; otherwise, set mark at the current value of point
     and point at the click position.  Save the resulting region in the
     kill ring; on a second click, kill it (`mouse-save-then-kill').

   The most basic mouse command is `mouse-set-point', which is called
by clicking with the left mouse button, `Mouse-1', in the text area of
a window.  This moves point to the position where you clicked.

   Normally, Emacs does not distinguish between ordinary mouse clicks
and clicks that select a frame.  When you click on a frame to select
it, that also changes the selected window and cursor position according
to the mouse click position.  On the X window system, you can change
this behavior by setting the variable
`x-mouse-click-focus-ignore-position' to `t'.  Then the first click
selects the frame, but does not affect the selected window or cursor
position.  If you click again in the same place, that click will be in
the selected frame, so it will change the window or cursor position.

   Holding down `Mouse-1' and "dragging" the mouse over a stretch of
text activates the region around that text (`mouse-set-region').  *Note
Mark::.  Emacs places the mark where you started holding down the mouse
button, and point where you release it.  In addition, the region is
copied into the kill ring (*note Kill Ring::).  If you don't want Emacs
to copy the region, change the variable `mouse-drag-copy-region' to
`nil'.

   If you move the mouse off the top or bottom of the window while
dragging, the window scrolls at a steady rate until you move the mouse
back into the window.  This way, you can select regions that don't fit
entirely on the screen.  The number of lines scrolled per step depends
on how far away from the window edge the mouse has gone; the variable
`mouse-scroll-min-lines' specifies a minimum step size.

   Clicking with the middle mouse button, `Mouse-2', moves point to the
position where you clicked and performs a yank (`mouse-yank-at-click').
*Note Yanking::.  If you change the variable `mouse-yank-at-point' to a
non-`nil' value, `Mouse-2' does not move point.  Then it does not
matter where you click, or even which of the frame's windows you click
on; the yank occurs at the existing point.  This variable also affects
yanking the primary and secondary selections (*note Cut/Paste Other
App::).

   Clicking with the right mouse button, `Mouse-3', runs the command
`mouse-save-then-kill'.  This performs several actions depending on
where you click and the status of the region:

   * If no region is active, clicking `Mouse-3' activates the region,
     placing the mark where point was and point at the clicked position.
     In addition, the text in the region is copied to the kill ring.

   * If a region is active, clicking `Mouse-3' adjusts the nearer end
     of the region by moving it to the clicked position.  The adjusted
     region's text is copied to the kill ring; if the text in the
     original region was already on the kill ring, it replaces it there.

   * If you originally specified the region using a double or triple
     `Mouse-1', so that the region is defined to consist of entire
     words or lines, then adjusting the region with `Mouse-3' also
     proceeds by entire words or lines.

   * If you use `Mouse-3' a second time consecutively, at the same
     place, that kills the region already selected.  Thus, the simplest
     way to kill text with the mouse is to click `Mouse-1' at one end,
     then click `Mouse-3' twice at the other end.  To copy the text
     into the kill ring without deleting it from the buffer, press
     `Mouse-3' just once--or just drag across the text with `Mouse-1'.
     Then you can copy it elsewhere by yanking it.

   Whenever you set the region using any of the mouse commands
described above, the mark will be deactivated by any subsequent
unshifted cursor motion command, in addition to the usual ways of
deactivating the mark.  *Note Shift Selection::.  While the region
remains active, typing <Backspace> or <Delete> deletes the text in that
region and deactivates the mark; this behavior follows a convention
established by other graphical programs, and it does _not_ apply when
you set the region any other way, including shift-selection (*note
Shift Selection::).

   Many graphical applications also follow the convention that
insertion while text is selected deletes the selected text.  You can
make Emacs behave this way by enabling Delete Selection mode.  *Note
Using Region::.


File: emacs,  Node: Word and Line Mouse,  Next: Cut/Paste Other App,  Prev: Mouse Commands,  Up: Cut and Paste

25.1.2 Mouse Commands for Words and Lines
-----------------------------------------

These variants of `Mouse-1' select entire words or lines at a time.
Emacs activates the region around the selected text, which is also
copied to the kill ring.

`Double-Mouse-1'
     Select the text around the word which you click on.

     Double-clicking on a character with "symbol" syntax (such as
     underscore, in C mode) selects the symbol surrounding that
     character.  Double-clicking on a character with open- or
     close-parenthesis syntax selects the parenthetical grouping which
     that character starts or ends.  Double-clicking on a character
     with string-delimiter syntax (such as a singlequote or doublequote
     in C) selects the string constant (Emacs uses heuristics to figure
     out whether that character is the beginning or the end of it).

`Double-Drag-Mouse-1'
     Select the text you drag across, in the form of whole words.

`Triple-Mouse-1'
     Select the line you click on.

`Triple-Drag-Mouse-1'
     Select the text you drag across, in the form of whole lines.


File: emacs,  Node: Cut/Paste Other App,  Next: Secondary Selection,  Prev: Word and Line Mouse,  Up: Cut and Paste

25.1.3 Cut and Paste with Other Window Applications
---------------------------------------------------

When running Emacs under the X window system, you can easily transfer
text between Emacs and other X applications using the "primary
selection" (also called the "X selection").  This is _not_ the same
thing as the "clipboard", which is a separate facility used on desktop
environments such as Gnome, and on operating systems such as Microsoft
Windows (*note Clipboard::).

   Under X, whenever you select some text in Emacs by dragging or
clicking the mouse (*note Mouse Commands::), it is also saved in the
primary selection.  You can then "paste" that text into any other X
application, usually by clicking `Mouse-2' in that application.  Unlike
the Emacs kill ring (*note Kill Ring::), the primary selection has no
"memory": each time you save something in the primary selection, either
in Emacs or in another X application, the previous contents of the
primary selection are lost.

   MS-Windows provides no primary selection, but Emacs emulates it
within a single Emacs session, by storing the selected text internally.
Therefore, all the features and commands related to the primary
selection work on Windows as they do on X, for cutting and pasting
within the same session, but not across Emacs sessions or with other
applications.

   Whenever you kill some text using a command such as `C-w'
(`kill-region'), or copy it into the kill ring using a command such as
`M-w' (`kill-ring-save'), that text is also saved in the primary
selection.  *Note Killing::.

   If you set the region using the keyboard--for instance, by typing
`C-<SPC>' and moving point away from the mark--the text in the region
is not normally saved to the primary selection.  However, if you change
the variable `select-active-regions' to `t', the region is saved to the
primary selection whenever you activate the mark.  Each change to the
region also updates the primary selection.

   If you change `yank-pop-change-selection' to `t', rotating the kill
ring with `M-y' (`yank-pop') also saves the new yank to the primary
selection (*note Yanking::).

   If you change `save-interprogram-paste-before-kill' to `t', each
kill command first saves the existing selection onto the kill ring.
This prevents you from losing the existing selection, at the risk of
large memory consumption if other applications generate large
selections.

   Whenever Emacs saves some text to the primary selection, it may also
save it to the "cut buffer".  The cut buffer is an obsolete predecessor
to the primary selection; most modern applications do not use it.
Saving text to the cut buffer is slow and inefficient, so Emacs only
does it if the text is shorter than the value of `x-cut-buffer-max'
(20000 characters by default).

   You can yank the primary selection into Emacs using the usual yank
commands, such as `C-y' (`yank') and `Mouse-2' (`mouse-yank-at-click').
These commands actually check the primary selection before referring to
the kill ring; if no primary selection is available, the kill ring
contents are used.  To prevent yank commands from accessing the primary
selection, set the variable `x-select-enable-primary' to `nil'.

   The standard coding system for the primary selection is
`compound-text-with-extensions'.  You may find that the pasted text is
not what you expected.  In such a case, you can specify another coding
system for the selection by typing `C-x <RET> x' or `C-x <RET> X'.
Alternatively, you can request a different data type by modifying the
variable `x-select-request-type'.  *Note Communication Coding::.


File: emacs,  Node: Secondary Selection,  Next: Clipboard,  Prev: Cut/Paste Other App,  Up: Cut and Paste

25.1.4 Secondary Selection
--------------------------

In addition to the primary selection, the X Window System provides a
second similar facility known as the "secondary selection".  Nowadays,
few X applications make use of the secondary selection, but you can
access it using the following Emacs commands:

`M-Drag-Mouse-1'
     Set the secondary selection, with one end at the place where you
     press down the button, and the other end at the place where you
     release it (`mouse-set-secondary').  The selected text is
     highlighted, using the `secondary-selection' face, as you drag.
     The window scrolls automatically if you drag the mouse off the top
     or bottom of the window, just like `mouse-set-region' (*note Mouse
     Commands::).

     This command does not alter the kill ring.

`M-Mouse-1'
     Set one endpoint for the "secondary selection"
     (`mouse-start-secondary').

`M-Mouse-3'
     Set the secondary selection, with one end at the position clicked
     and the other at the position specified with `M-Mouse-1'
     (`mouse-secondary-save-then-kill').  This also puts the selected
     text in the kill ring.  A second `M-Mouse-3' at the same place
     kills the secondary selection just made.

`M-Mouse-2'
     Insert the secondary selection where you click, placing point at
     the end of the yanked text (`mouse-yank-secondary').

   Double or triple clicking of `M-Mouse-1' operates on words and
lines, much like `Mouse-1'.

   If `mouse-yank-at-point' is non-`nil', `M-Mouse-2' yanks at point.
Then it does not matter precisely where you click, or even which of the
frame's windows you click on.  *Note Mouse Commands::.


File: emacs,  Node: Clipboard,  Prev: Secondary Selection,  Up: Cut and Paste

25.1.5 Using the Clipboard
--------------------------

In desktop environments such as Gnome, and operating systems such as
Microsoft Windows and Mac OS X, you can transfer data (usually text)
between different applications using the "clipboard".  The clipboard is
distinct from the primary selection and secondary selection discussed
earlier.  You can access the clipboard through the `Edit' menu of the
menu bar (*note Menu Bar::).

   The command `clipboard-kill-region', which is bound to the `Cut'
menu item, kills the region and saves it in the clipboard.

   The command `clipboard-kill-ring-save', which is bound to the `Copy'
menu item, copies the region to the kill ring and saves it in the
clipboard.

   The `Paste' menu item in the Edit menu yanks the contents of the
clipboard at point (`clipboard-yank').

   You can customize the variable `x-select-enable-clipboard' to make
the Emacs yank functions consult the clipboard before the primary
selection, and to make the kill functions to store in the clipboard as
well as the primary selection.  Otherwise, these commands do not access
the clipboard at all.  Using the clipboard is the default on MS-Windows
and Mac OS, but not on other systems.


File: emacs,  Node: Mouse References,  Next: Menu Mouse Clicks,  Prev: Cut and Paste,  Up: Frames

25.2 Following References with the Mouse
========================================

Some Emacs buffers include "buttons".  A button is a piece of text that
performs some action when you activate it, such as following a
reference.  Usually, a button's text is visually highlighted: it is
underlined, or a box is drawn around it.  If you move the mouse over a
button, the shape of the mouse cursor changes and the button lights up
(if you change the variable `mouse-highlight' to `nil', Emacs disables
this highlighting).

   You can activate a button by moving point to it and typing <RET>, or
by clicking either `Mouse-1' or `Mouse-2' on the button.  For example,
typing <RET> or clicking on a file name in a Dired buffer visits that
file (*note Dired::).  Doing it on an error message in the
`*Compilation*' buffer goes to the source code for that error message
(*note Compilation::).  Doing it on a completion in the `*Completions*'
buffer chooses that completion (*note Completion::).

   Although clicking `Mouse-1' on a button usually activates that
button, if you hold the mouse button down for a short period of time
before releasing it (specifically, for more than 450 milliseconds),
then Emacs moves point where you clicked instead.  This behavior allows
you to use the mouse to move point over a button without following it.
Dragging--moving the mouse while it is held down--has its usual
behavior of setting the region, even if you drag from or onto a button.

   Normally, clicking `Mouse-1' on a button activates the button even
if it is in a nonselected window.  If you change the variable
`mouse-1-click-in-non-selected-windows' to `nil', clicking `Mouse-1' on
a button in an un-selected window moves point to the clicked position
and selects that window, without activating the button.

   In Emacs versions before 22, only `Mouse-2' activates buttons and
`Mouse-1' always sets point.  If you prefer this older behavior, set
the variable `mouse-1-click-follows-link' to `nil'.  This variable also
lets you choose various other alternatives for following links with the
mouse.  Type `C-h v mouse-1-click-follows-link <RET>' for more details.


File: emacs,  Node: Menu Mouse Clicks,  Next: Mode Line Mouse,  Prev: Mouse References,  Up: Frames

25.3 Mouse Clicks for Menus
===========================

Several mouse clicks with the <CTRL> and <SHIFT> modifiers bring up
menus.

`C-Mouse-1'
     This menu is for selecting a buffer.

     The MSB ("mouse select buffer") global minor mode makes this menu
     smarter and more customizable.  *Note Buffer Menus::.

`C-Mouse-2'
     This menu is for specifying faces and other text properties for
     editing formatted text.  *Note Formatted Text::.

`C-Mouse-3'
     This menu is mode-specific.  For most modes if Menu-bar mode is on,
     this menu has the same items as all the mode-specific menu-bar
     menus put together.  Some modes may specify a different menu for
     this button.(1)  If Menu-bar mode is off, this menu contains all
     the items which would be present in the menu bar--not just the
     mode-specific ones--so that you can access them without having to
     display the menu bar.

`S-Mouse-1'
     This menu is for changing the default face within the window's
     buffer.  *Note Temporary Face Changes::.

   ---------- Footnotes ----------

   (1) Some systems use `Mouse-3' for a mode-specific menu.  We took a
survey of users, and found they preferred to keep `Mouse-3' for
selecting and killing regions.  Hence the decision to use `C-Mouse-3'
for this menu.  To use `Mouse-3' instead, do `(global-set-key [mouse-3]
'mouse-popup-menubar-stuff)'.


File: emacs,  Node: Mode Line Mouse,  Next: Creating Frames,  Prev: Menu Mouse Clicks,  Up: Frames

25.4 Mode Line Mouse Commands
=============================

You can use mouse clicks on window mode lines to select and manipulate
windows.

   Some areas of the mode line, such as the buffer name, and major and
minor mode names, have their own special mouse bindings.  These areas
are highlighted when you hold the mouse over them, and information about
the special bindings will be displayed (*note Tooltips::).  This
section's commands do not apply in those areas.

`Mouse-1'
     `Mouse-1' on a mode line selects the window it belongs to.  By
     dragging `Mouse-1' on the mode line, you can move it, thus
     changing the height of the windows above and below.  Changing
     heights with the mouse in this way never deletes windows, it just
     refuses to make any window smaller than the minimum height.

`Mouse-2'
     `Mouse-2' on a mode line expands that window to fill its frame.

`Mouse-3'
     `Mouse-3' on a mode line deletes the window it belongs to.  If the
     frame has only one window, it buries the current buffer instead,
     and switches to another buffer.

`C-Mouse-2'
     `C-Mouse-2' on a mode line splits the window above horizontally,
     above the place in the mode line where you click.

   Using `Mouse-1' on the divider between two side-by-side mode lines,
you can move the vertical boundary left or right.  Using `C-Mouse-2' on
a scroll bar splits the corresponding window vertically.  *Note Split
Window::.


File: emacs,  Node: Creating Frames,  Next: Frame Commands,  Prev: Mode Line Mouse,  Up: Frames

25.5 Creating Frames
====================

The prefix key `C-x 5' is analogous to `C-x 4', with parallel
subcommands.  The difference is that `C-x 5' commands create a new
frame rather than just a new window in the selected frame (*note Pop Up
Window::).  If an existing visible or iconified ("minimized") frame
already displays the requested material, these commands use the
existing frame, after raising or deiconifying ("un-minimizing") as
necessary.

   The various `C-x 5' commands differ in how they find or create the
buffer to select:

`C-x 5 2'
     Create a new frame (`make-frame-command').

`C-x 5 b BUFNAME <RET>'
     Select buffer BUFNAME in another frame.  This runs
     `switch-to-buffer-other-frame'.

`C-x 5 f FILENAME <RET>'
     Visit file FILENAME and select its buffer in another frame.  This
     runs `find-file-other-frame'.  *Note Visiting::.

`C-x 5 d DIRECTORY <RET>'
     Select a Dired buffer for directory DIRECTORY in another frame.
     This runs `dired-other-frame'.  *Note Dired::.

`C-x 5 m'
     Start composing a mail message in another frame.  This runs
     `mail-other-frame'.  It is the other-frame variant of `C-x m'.
     *Note Sending Mail::.

`C-x 5 .'
     Find a tag in the current tag table in another frame.  This runs
     `find-tag-other-frame', the multiple-frame variant of `M-.'.
     *Note Tags::.

`C-x 5 r FILENAME <RET>'
     Visit file FILENAME read-only, and select its buffer in another
     frame.  This runs `find-file-read-only-other-frame'.  *Note
     Visiting::.

   You can control the appearance of new frames you create by setting
the frame parameters in `default-frame-alist'.  You can use the
variable `initial-frame-alist' to specify parameters that affect only
the initial frame.  *Note Initial Parameters: (elisp)Initial
Parameters, for more information.

   Here is an example of using `default-frame-alist' to specify the
default foreground color and font:

     (add-to-list 'default-frame-alist '(font . "10x20"))
     (add-to-list 'default-frame-alist
                  '(foreground-color . "blue"))

By putting such customizations in your init file, you can control the
appearance of all the frames Emacs creates, including the initial one
(*note Init File::).  *Note Fonts::, for other ways to set the default
font.


File: emacs,  Node: Frame Commands,  Next: Fonts,  Prev: Creating Frames,  Up: Frames

25.6 Frame Commands
===================

The following commands let you create, delete and operate on frames:

`C-z'
     Minimize (or "iconify) the selected Emacs frame (`suspend-frame').
     *Note Exiting::.

`C-x 5 0'
     Delete the selected frame (`delete-frame').  This is not allowed
     if there is only one frame.

`C-x 5 o'
     Select another frame, raise it, and warp the mouse to it.  If you
     repeat this command, it cycles through all the frames on your
     terminal.

`C-x 5 1'
     Delete all frames except the selected one.

   The `C-x 5 0' (`delete-frame') command will never delete the last
frame, to prevent you from losing the ability to interact with the
Emacs process.  Note that when Emacs is run as a daemon (*note Emacs
Server::), there is always a "virtual frame" that remains after all the
ordinary, interactive frames are deleted.  In this case, `C-x 5 0' can
delete the last interactive frame; you can use `emacsclient' to
reconnect to the Emacs session.

   On X, you may have to tell Emacs how the system (or the window
manager) handles focus-switching between windows, in order for the
command `C-x 5 o' (`other-frame') to work properly.  Unfortunately,
there is no way for Emacs to detect this automatically, so you should
set the variable `focus-follows-mouse'.  If simply moving the mouse
onto a window selects it and gives it focus, the variable should be
`t'; if you have to click on the window to select it, the variable
should be `nil'.  The default is `t'.

   The window manager that is part of MS-Windows always gives focus to
a frame that raises, so this variable has no effect in the native
MS-Windows build of Emacs.


File: emacs,  Node: Fonts,  Next: Speedbar,  Prev: Frame Commands,  Up: Frames

25.7 Fonts
==========

By default, Emacs displays text in X using a 12-point monospace font.
There are several different ways to specify a different font:

   * Click on `Set Default Font' in the `Options' menu.  To save this
     for future sessions, click on `Save Options' in the `Options' menu.

   * Add a line to your init file (*note Init File::), modifying the
     variable `default-frame-alist' to specify the `font' parameter
     (*note Creating Frames::), like this:

          (add-to-list 'default-frame-alist '(font . "DejaVu Sans Mono-12"))

   * Add an `emacs.font' X resource setting to your X resource file,
     like this:

          emacs.font: DejaVu Sans Mono-12

     You must restart X, or use the `xrdb' command, for the X resources
     file to take effect.  *Note Resources::.  When specifying a font
     in your X resources file, you should not quote it.

   * If you are running Emacs on the GNOME desktop, you can tell Emacs
     to use the default system font by setting the variable
     `font-use-system-font' to `t' (the default is `nil').  For this to
     work, Emacs must be compiled with Gconf support; this is done
     automatically if the libraries are present at compile time.

   * Use the command line option `-fn' (or `--font').  *Note Font X::.

   On X, there are four different ways to express a "font name".  The
first is to use a "Fontconfig pattern".  Fontconfig patterns have the
following form:

     FONTNAME[-FONTSIZE][:NAME1=VALUES1][:NAME2=VALUES2]...

Within this format, any of the elements in braces may be omitted.
Here, FONTNAME is the "family name" of the font, such as `Monospace' or
`DejaVu Serif'; FONTSIZE is the "point size" of the font (one
"printer's point" is about 1/72 of an inch); and the `NAME=VALUES'
entries specify settings such as the slant and weight of the font.
Each VALUES may be a single value, or a list of values separated by
commas.  In addition, some property values are valid with only one kind
of property name, in which case the `NAME=' part may be omitted.

   Here is a list of common font properties:

`slant'
     One of `italic', `oblique' or `roman'.

`weight'
     One of `light', `medium', `demibold', `bold' or `black'.

`style'
     Some fonts define special styles which are a combination of slant
     and weight.  For instance, `Dejavu Sans' defines the `book' style,
     which overrides the slant and weight properties.

`width'
     One of `condensed', `normal', or `expanded'.

`spacing'
     One of `monospace', `proportional', `dual-width', or `charcell'.

Here are some examples of Fontconfig patterns:

     Monospace
     Monospace-12
     Monospace-12:bold
     DejaVu Sans Mono:bold:italic
     Monospace-12:weight=bold:slant=italic

   For a more detailed description of Fontconfig patterns, see the
Fontconfig manual, which is distributed with Fontconfig and available
online at `http://fontconfig.org/fontconfig-user.html'.

   The second way to specify a font is to use a "GTK font description".
These have the syntax

     FONTNAME [PROPERTIES] [FONTSIZE]

where FONTNAME is the family name, PROPERTIES is a list of property
values separated by spaces, and FONTSIZE is the point size.  The
properties that you may specify are as follows:

`style'
     One of `roman', `italic' or `oblique'.  If omitted, the `roman'
     style is used.

`weight'
     One of `medium', `ultra-light', `light', `semi-bold', or `bold'.
     If omitted, `medium' weight is used.

Here are some examples of GTK font descriptions:

     Monospace 12
     Monospace Bold Italic 12

   The third way to specify a font is to use an "XLFD" ("X Logical Font
Description").  This is the traditional method for specifying fonts
under X.  Each XLFD consists of fourteen words or numbers, separated by
dashes, like this:

     -misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1

A wildcard character (`*') in an XLFD matches any sequence of
characters (including none), and `?' matches any single character.
However, matching is implementation-dependent, and can be inaccurate
when wildcards match dashes in a long name.  For reliable results,
supply all 14 dashes and use wildcards only within a field.  Case is
insignificant in an XLFD.  The syntax for an XLFD is as follows:

     -MAKER-FAMILY-WEIGHT-SLANT-WIDTHTYPE-STYLE...
     ...-PIXELS-HEIGHT-HORIZ-VERT-SPACING-WIDTH-REGISTRY-ENCODING

The entries have the following meanings:

MAKER
     The name of the font manufacturer.

FAMILY
     The name of the font family (e.g. `courier').

WEIGHT
     The font weight--normally either `bold', `medium' or `light'.
     Some font names support other values.

SLANT
     The font slant--normally `r' (roman), `i' (italic), `o' (oblique),
     `ri' (reverse italic), or `ot' (other).  Some font names support
     other values.

WIDTHTYPE
     The font width--normally `normal', `condensed', `extended', or
     `semicondensed' (some font names support other values).

STYLE
     An optional additional style name.  Usually it is empty--most long
     font names have two hyphens in a row at this point.

PIXELS
     The font height, in pixels.

HEIGHT
     The font height on the screen, measured in tenths of a printer's
     point.  This is the point size of the font, times ten.  For a given
     vertical resolution, HEIGHT and PIXELS are proportional;
     therefore, it is common to specify just one of them and use `*'
     for the other.

HORIZ
     The horizontal resolution, in pixels per inch, of the screen for
     which the font is intended.

VERT
     The vertical resolution, in pixels per inch, of the screen for
     which the font is intended.  Normally the resolution of the fonts
     on your system is the right value for your screen; therefore, you
     normally specify `*' for this and HORIZ.

SPACING
     This is `m' (monospace), `p' (proportional) or `c' (character
     cell).

WIDTH
     The average character width, in pixels, multiplied by ten.

REGISTRY
ENCODING
     The X font character set that the font depicts.  (X font character
     sets are not the same as Emacs character sets, but they are
     similar.)  You can use the `xfontsel' program to check which
     choices you have.  Normally you should use `iso8859' for REGISTRY
     and `1' for ENCODING.

   The fourth and final method of specifying a font is to use a "font
nickname".  Certain fonts have shorter nicknames, which you can use
instead of a normal font specification.  For instance, `6x13' is
equivalent to

     -misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1

   On X, Emacs recognizes two types of fonts: "client-side" fonts,
which are provided by the Xft and Fontconfig libraries, and
"server-side" fonts, which are provided by the X server itself.  Most
client-side fonts support advanced font features such as antialiasing
and subpixel hinting, while server-side fonts do not.  Fontconfig and
GTK patterns match only client-side fonts.

   You will probably want to use a fixed-width default font--that is, a
font in which all characters have the same width.  For Xft and
Fontconfig fonts, you can use the `fc-list' command to list the
available fixed-width fonts, like this:

     fc-list :spacing=mono fc-list :spacing=charcell

For server-side X fonts, you can use the `xlsfonts' program to list the
available fixed-width fonts, like this:

     xlsfonts -fn '*x*' | egrep "^[0-9]+x[0-9]+"
     xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-m*'
     xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-c*'

Any font with `m' or `c' in the SPACING field of the XLFD is a
fixed-width font.  To see what a particular font looks like, use the
`xfd' command.  For example:

     xfd -fn 6x13

displays the entire font `6x13'.

   While running Emacs, you can also set the font of a specific kind of
text (*note Faces::), or a particular frame (*note Frame Parameters::).


File: emacs,  Node: Speedbar,  Next: Multiple Displays,  Prev: Fonts,  Up: Frames

25.8 Speedbar Frames
====================

The "speedbar" is a special frame for conveniently navigating in or
operating on another frame.  The speedbar, when it exists, is always
associated with a specific frame, called its "attached frame"; all
speedbar operations act on that frame.

   Type `M-x speedbar' to create the speedbar and associate it with the
current frame.  To dismiss the speedbar, type `M-x speedbar' again, or
select the speedbar and type `q'.  (You can also delete the speedbar
frame like any other Emacs frame.)  If you wish to associate the
speedbar with a different frame, dismiss it and call `M-x speedbar'
from that frame.

   The speedbar can operate in various modes.  Its default mode is
"File Display" mode, which shows the files in the current directory of
the selected window of the attached frame, one file per line.  Clicking
on a file name visits that file in the selected window of the attached
frame, and clicking on a directory name shows that directory in the
speedbar (*note Mouse References::).  Each line also has a box, `[+]'
or `<+>', that you can click on to "expand" the contents of that item.
Expanding a directory adds the contents of that directory to the
speedbar display, underneath the directory's own line.  Expanding an
ordinary file adds a list of the tags in that file to the speedbar
display; you can click on a tag name to jump to that tag in the
selected window of the attached frame.  When a file or directory is
expanded, the `[+]' changes to `[-]'; you can click on that box to
"contract" the item, hiding its contents.

   You navigate through the speedbar using the keyboard, too.  Typing
`RET' while point is on a line in the speedbar is equivalent to
clicking the item on the current line, and `SPC' expands or contracts
the item.  `U' displays the parent directory of the current directory.
To copy, delete, or rename the file on the current line, type `C', `D',
and `R' respectively.  To create a new directory, type `M'.

   Another general-purpose speedbar mode is "Buffer Display" mode; in
this mode, the speedbar displays a list of Emacs buffers.  To switch to
this mode, type `b' in the speedbar.  To return to File Display mode,
type `f'.  You can also change the display mode by clicking `mouse-3'
anywhere in the speedbar window (or `mouse-1' on the mode-line) and
selecting `Displays' in the pop-up menu.

   Some major modes, including Rmail mode, Info, and GUD, have
specialized ways of putting useful items into the speedbar for you to
select.  For example, in Rmail mode, the speedbar shows a list of Rmail
files, and lets you move the current message to another Rmail file by
clicking on its `<M>' box.

   For more details on using and programming the speedbar, *Note
Speedbar: (speedbar)Top.


File: emacs,  Node: Multiple Displays,  Next: Special Buffer Frames,  Prev: Speedbar,  Up: Frames

25.9 Multiple Displays
======================

A single Emacs can talk to more than one X display.  Initially, Emacs
uses just one display--the one specified with the `DISPLAY' environment
variable or with the `--display' option (*note Initial Options::).  To
connect to another display, use the command `make-frame-on-display':

`M-x make-frame-on-display <RET> DISPLAY <RET>'
     Create a new frame on display DISPLAY.

   A single X server can handle more than one screen.  When you open
frames on two screens belonging to one server, Emacs knows they share a
single keyboard, and it treats all the commands arriving from these
screens as a single stream of input.

   When you open frames on different X servers, Emacs makes a separate
input stream for each server.  Each server also has its own selected
frame.  The commands you enter with a particular X server apply to that
server's selected frame.

   It is even possible to use this feature to let two or more users
type simultaneously on the two displays, within the same Emacs job.  In
practice, however, the different users can easily interfere with each
others' edits if they are not careful.


File: emacs,  Node: Special Buffer Frames,  Next: Frame Parameters,  Prev: Multiple Displays,  Up: Frames

25.10 Special Buffer Frames
===========================

You can make certain chosen buffers, which Emacs normally displays in
"another window," appear in special frames of their own.  To do this,
set the variable `special-display-buffer-names' to a list of buffer
names; any buffer whose name is in that list automatically gets a
special frame, when an Emacs command wants to display it "in another
window."

   For example, if you set the variable this way,

     (setq special-display-buffer-names
           '("*Completions*" "*grep*" "*tex-shell*"))

then completion lists, `grep' output and the TeX mode shell buffer get
individual frames of their own.  These frames, and the windows in them,
are never automatically split or reused for any other buffers.  They
continue to show the buffers they were created for, unless you alter
them by hand.  Killing the special buffer deletes its frame
automatically.

   More generally, you can set `special-display-regexps' to a list of
regular expressions; then a buffer gets its own frame if its name
matches any of those regular expressions.  (Once again, this applies
only to buffers that normally get displayed for you in "another
window.")

   The variable `special-display-frame-alist' specifies the frame
parameters for these frames.  It has a default value, so you don't need
to set it.

   For those who know Lisp, an element of
`special-display-buffer-names' or `special-display-regexps' can also be
a list.  Then the first element is the buffer name or regular
expression; the rest of the list specifies how to create the frame.  It
can be an association list specifying frame parameter values; these
values take precedence over parameter values specified in
`special-display-frame-alist'.  If you specify the symbol `same-window'
as a "frame parameter" in this list, with a non-`nil' value, that means
to use the selected window if possible.  If you use the symbol
`same-frame' as a "frame parameter" in this list, with a non-`nil'
value, that means to use the selected frame if possible.

   Alternatively, the value can have this form:

     (FUNCTION ARGS...)

where FUNCTION is a symbol.  Then the frame is constructed by calling
FUNCTION; its first argument is the buffer, and its remaining arguments
are ARGS.

   An analogous feature lets you specify buffers which should be
displayed in the selected window.  *Note Force Same Window::.  The
same-window feature takes precedence over the special-frame feature;
therefore, if you add a buffer name to `special-display-buffer-names'
and it has no effect, check to see whether that feature is also in use
for the same buffer name.


File: emacs,  Node: Frame Parameters,  Next: Scroll Bars,  Prev: Special Buffer Frames,  Up: Frames

25.11 Setting Frame Parameters
==============================

These commands are available for controlling the window management
behavior of the selected frame:

`M-x auto-raise-mode'
     Toggle whether or not the selected frame should auto-raise.
     Auto-raise means that every time you move the mouse onto the
     frame, it raises the frame.

     Some window managers also implement auto-raise.  If you enable
     auto-raise for Emacs frames in your window manager, it will work,
     but it is beyond Emacs' control, so `auto-raise-mode' has no effect
     on it.

`M-x auto-lower-mode'
     Toggle whether or not the selected frame should auto-lower.
     Auto-lower means that every time you move the mouse off the frame,
     the frame moves to the bottom of the stack on the screen.

     The command `auto-lower-mode' has no effect on auto-lower
     implemented by the window manager.  To control that, you must use
     the appropriate window manager features.

   In Emacs versions that use an X toolkit, the color-setting and
font-setting functions don't affect menus and the menu bar, since they
are displayed by their own widget classes.  To change the appearance of
the menus and menu bar, you must use X resources (*note Resources::).
*Note Colors::, regarding colors.  *Note Font X::, regarding choice of
font.

   Colors, fonts, and other attributes of the frame's display can also
be customized by setting frame parameters in the variable
`default-frame-alist' (*note Creating Frames::).  For a detailed
description of frame parameters and customization, see *note Frame
Parameters: (elisp)Frame Parameters.


File: emacs,  Node: Scroll Bars,  Next: Wheeled Mice,  Prev: Frame Parameters,  Up: Frames

25.12 Scroll Bars
=================

On graphical displays, Emacs normally makes a "scroll bar" at the left
of each Emacs window, running the height of the window.(1)

   When Emacs is compiled with GTK+ support on the X window system, or
in operating systems such as Microsoft Windows or Mac OS, you can use
the scroll bar as you do in other graphical applications.  If you click
`Mouse-1' on the scroll bar's up and down buttons, that scrolls the
window by one line at a time.  Clicking `Mouse-1' above or below the
scroll bar's inner box scrolls the window by nearly the entire height
of the window, like `M-v' and `C-v' respectively (*note Moving
Point::).  Dragging the inner box with `Mouse-1' scrolls the window
continuously.

   If Emacs is compiled without GTK+ support on the X window system,
the scroll bar behaves differently.  The scroll bar's inner box is
drawn to represent the portion of the buffer currently displayed, with
the entire height of the scroll bar representing the entire length of
the buffer.  `Mouse-1' anywhere on the scroll bar scrolls forward like
`C-v', and `Mouse-3' scrolls backward like `M-v'.  Clicking `Mouse-2'
in the scroll bar lets you move or drag the inner box up and down.

   You can also click `C-Mouse-2' in the scroll bar to split a window
vertically.  The split occurs on the line where you click.

   You can toggle the use of the scroll bar with the command `M-x
scroll-bar-mode'.  With a prefix argument, this command turns use of
scroll bars on if and only if the argument is positive.  This command
applies to all frames, including frames yet to be created.  Customize
the variable `scroll-bar-mode' to control the use of scroll bars at
startup.  You can use it to specify that they are placed at the right
of windows if you prefer that.  You have to set this variable through
the `Customize' interface (*note Easy Customization::), or it will not
work properly.  You can also use the X resource `verticalScrollBars' to
control the initial setting of Scroll Bar mode.  *Note Resources::.

   To enable or disable scroll bars for just the selected frame, use the
command `M-x toggle-scroll-bar'.

   You can control the scroll bar width by changing the value of the
`scroll-bar-width' frame parameter.

   ---------- Footnotes ----------

   (1) Placing it at the left is usually more useful with overlapping
frames with text starting at the left margin.


File: emacs,  Node: Wheeled Mice,  Next: Drag and Drop,  Prev: Scroll Bars,  Up: Frames

25.13 Scrolling With "Wheeled" Mice
===================================

Some mice have a "wheel" instead of a third button.  You can usually
click the wheel to act as either `Mouse-2' or `Mouse-3', depending on
the setup.  You can also use the wheel to scroll windows instead of
using the scroll bar or keyboard commands.  Mouse wheel support only
works if the system generates appropriate events; whenever possible, it
is turned on by default.  To toggle this feature, use `M-x
mouse-wheel-mode'.

   The two variables `mouse-wheel-follow-mouse' and
`mouse-wheel-scroll-amount' determine where and by how much buffers are
scrolled.  The variable `mouse-wheel-progressive-speed' determines
whether the scroll speed is linked to how fast you move the wheel.


File: emacs,  Node: Drag and Drop,  Next: Menu Bars,  Prev: Wheeled Mice,  Up: Frames

25.14 Drag and Drop
===================

Emacs supports "drag and drop" using the mouse.  For instance, dropping
text onto an Emacs frame inserts the text where it is dropped.
Dropping a file onto an Emacs frame visits that file.  As a special
case, dropping the file on a Dired buffer moves or copies the file
(according to the conventions of the application it came from) into the
directory displayed in that buffer.

   Dropping a file normally visits it in the window you drop it on.  If
you prefer to visit the file in a new window in such cases, customize
the variable `dnd-open-file-other-window'.

   The XDND and Motif drag and drop protocols, and the old KDE 1.x
protocol, are currently supported.


File: emacs,  Node: Menu Bars,  Next: Tool Bars,  Prev: Drag and Drop,  Up: Frames

25.15 Menu Bars
===============

You can turn display of menu bars on or off with `M-x menu-bar-mode' or
by customizing the variable `menu-bar-mode'.  With no argument, this
command toggles Menu Bar mode, a minor mode.  With an argument, the
command turns Menu Bar mode on if the argument is positive, off if the
argument is not positive.  You can use the X resource `menuBar' to
control the initial setting of Menu Bar mode.  *Note Resources::.

   Expert users often turn off the menu bar, especially on text-only
terminals, where this makes one additional line available for text.  If
the menu bar is off, you can still pop up a menu of its contents with
`C-Mouse-3' on a display which supports pop-up menus.  *Note Menu Mouse
Clicks::.

   *Note Menu Bar::, for information on how to invoke commands with the
menu bar.  *Note X Resources::, for how to customize the menu bar
menus' visual appearance.


File: emacs,  Node: Tool Bars,  Next: Dialog Boxes,  Prev: Menu Bars,  Up: Frames

25.16 Tool Bars
===============

The "tool bar" is a line (or lines) of icons at the top of the Emacs
window, just below the menu bar.  You can click on these icons with the
mouse to do various jobs.

   The global tool bar contains general commands.  Some major modes
define their own tool bars to replace it.  A few "special" modes that
are not designed for ordinary editing remove some items from the global
tool bar.

   Tool bars work only on a graphical display.  The tool bar uses
colored XPM icons if Emacs was built with XPM support.  Otherwise, the
tool bar uses monochrome icons (PBM or XBM format).

   You can turn display of tool bars on or off with `M-x tool-bar-mode'
or by customizing the option `tool-bar-mode'.


File: emacs,  Node: Dialog Boxes,  Next: Tooltips,  Prev: Tool Bars,  Up: Frames

25.17 Using Dialog Boxes
========================

A dialog box is a special kind of menu for asking you a yes-or-no
question or some other special question.  Many Emacs commands use a
dialog box to ask a yes-or-no question, if you used the mouse to invoke
the command that led to the question.

   To disable the use of dialog boxes, change the variable
`use-dialog-box' to `nil'.  In that case, Emacs always performs
yes-or-no prompts using the echo area and keyboard input.  This
variable also controls whether to use file selection windows (but those
are not supported on all platforms).

   A file selection window is a special kind of dialog box for asking
for file names.  You can customize the variable `use-file-dialog' to
suppress the use of file selection windows, even if you still want
other kinds of dialogs.  This variable has no effect if you have
suppressed all dialog boxes with the variable `use-dialog-box'.

   When Emacs is compiled with GTK+ support, it uses the GTK+ "file
chooser" dialog.  Emacs adds an additional toggle button to this
dialog, which you can use to enable or disable the display of hidden
files (files starting with a dot) in that dialog.  If you want this
toggle to be activated by default, change the variable
`x-gtk-show-hidden-files' to `t'.  In addition, Emacs adds help text to
the GTK+ file chooser dialog; to disable this help text, change the
variable `x-gtk-file-dialog-help-text' to `nil'.

   In GTK+ versions 2.4 through 2.10, you can choose to use an older
version of the GTK+ file dialog by setting the variable
`x-gtk-use-old-file-dialog' to a non-`nil' value.  If Emacs is built
with a GTK+ version that has only one file dialog, this variable has no
effect.


File: emacs,  Node: Tooltips,  Next: Mouse Avoidance,  Prev: Dialog Boxes,  Up: Frames

25.18 Tooltips
==============

"Tooltips" are small windows that display text information at the
current mouse position.  They activate when there is a pause in mouse
movement.  There are two types of tooltip: help tooltips and GUD
tooltips.

   "Help tooltips" typically display over text--including the mode
line--but are also available for other parts of the Emacs frame, such
as the tool bar and menu items.

   You can toggle display of help tooltips (Tooltip mode) with the
command `M-x tooltip-mode'.  When Tooltip mode is disabled, the help
text is displayed in the echo area instead.

   "GUD tooltips" show values of variables.  They are useful when you
are debugging a program.  *Note Debugger Operation::.

   The variables `tooltip-delay' specifies how long Emacs should wait
before displaying a tooltip.  For additional customization options for
displaying tooltips, use `M-x customize-group <RET> tooltip <RET>'.
*Note X Resources::, for information on customizing the windows that
display tooltips.


File: emacs,  Node: Mouse Avoidance,  Next: Non-Window Terminals,  Prev: Tooltips,  Up: Frames

25.19 Mouse Avoidance
=====================

On graphical terminals, the mouse pointer may obscure the text in the
Emacs frame.  Emacs provides two methods to avoid this problem.

   Firstly, Emacs hides the mouse pointer each time you type a
self-inserting character, if the pointer lies inside an Emacs frame;
moving the mouse pointer makes it visible again.  To disable this
feature, set the variable `make-pointer-invisible' to `nil'.

   Secondly, you can use Mouse Avoidance mode, a minor mode, to keep
the mouse pointer away from point.  To use Mouse Avoidance mode,
customize the variable `mouse-avoidance-mode'.  You can set this to
various values to move the mouse in several ways:

`banish'
     Move the mouse to the upper-right corner on any key-press;

`exile'
     Move the mouse to the corner only if the cursor gets too close,
     and allow it to return once the cursor is out of the way;

`jump'
     If the cursor gets too close to the mouse, displace the mouse a
     random distance & direction;

`animate'
     As `jump', but shows steps along the way for illusion of motion;

`cat-and-mouse'
     The same as `animate';

`proteus'
     As `animate', but changes the shape of the mouse pointer too.

   You can also use the command `M-x mouse-avoidance-mode' to enable
the mode.  Whenever Mouse Avoidance mode moves the mouse, it also
raises the frame.


File: emacs,  Node: Non-Window Terminals,  Next: Text-Only Mouse,  Prev: Mouse Avoidance,  Up: Frames

25.20 Non-Window Terminals
==========================

On a text-only terminal, Emacs can display only one Emacs frame at a
time.  However, you can still create multiple Emacs frames, and switch
between them.  Switching frames on these terminals is much like
switching between different window configurations.

   Use `C-x 5 2' to create a new frame and switch to it; use `C-x 5 o'
to cycle through the existing frames; use `C-x 5 0' to delete the
current frame.

   Each frame has a number to distinguish it.  If your terminal can
display only one frame at a time, the selected frame's number N appears
near the beginning of the mode line, in the form `FN'.

   `FN' is in fact the frame's initial name.  You can give frames more
meaningful names if you wish, and you can select a frame by its name.
Use the command `M-x set-frame-name <RET> NAME <RET>' to specify a new
name for the selected frame, and use `M-x select-frame-by-name <RET>
NAME <RET>' to select a frame according to its name.  The name you
specify appears in the mode line when the frame is selected.


File: emacs,  Node: Text-Only Mouse,  Prev: Non-Window Terminals,  Up: Frames

25.21 Using a Mouse in Terminal Emulators
=========================================

Some text-only terminals support mouse clicks in the terminal window.

   In a terminal emulator which is compatible with `xterm', you can use
`M-x xterm-mouse-mode' to give Emacs control over simple use of the
mouse--basically, only non-modified single clicks are supported.  The
normal `xterm' mouse functionality for such clicks is still available
by holding down the `SHIFT' key when you press the mouse button.  Xterm
Mouse mode is a global minor mode (*note Minor Modes::).  Repeating the
command turns the mode off again.

   In the console on GNU/Linux, you can use `M-x gpm-mouse-mode' to
enable terminal mouse support.  You must have the gpm package installed
and running on your system in order for this to work.


File: emacs,  Node: International,  Next: Major Modes,  Prev: Frames,  Up: Top

26 International Character Set Support
**************************************

Emacs supports a wide variety of international character sets,
including European and Vietnamese variants of the Latin alphabet, as
well as Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek,
Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA,
Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts.
Emacs also supports various encodings of these characters used by other
internationalized software, such as word processors and mailers.

   Emacs allows editing text with international characters by supporting
all the related activities:

   * You can visit files with non-ASCII characters, save non-ASCII
     text, and pass non-ASCII text between Emacs and programs it
     invokes (such as compilers, spell-checkers, and mailers).  Setting
     your language environment (*note Language Environments::) takes
     care of setting up the coding systems and other options for a
     specific language or culture.  Alternatively, you can specify how
     Emacs should encode or decode text for each command; see *note
     Text Coding::.

   * You can display non-ASCII characters encoded by the various
     scripts.  This works by using appropriate fonts on graphics
     displays (*note Defining Fontsets::), and by sending special codes
     to text-only displays (*note Terminal Coding::).  If some
     characters are displayed incorrectly, refer to *note Undisplayable
     Characters::, which describes possible problems and explains how
     to solve them.

   * You can insert non-ASCII characters or search for them.  To do
     that, you can specify an input method (*note Select Input
     Method::) suitable for your language, or use the default input
     method set up when you set your language environment.  If your
     keyboard can produce non-ASCII characters, you can select an
     appropriate keyboard coding system (*note Terminal Coding::), and
     Emacs will accept those characters.  Latin-1 characters can also
     be input by using the `C-x 8' prefix, see *note Unibyte Mode::.

     On X Window systems, your locale should be set to an appropriate
     value to make sure Emacs interprets keyboard input correctly; see
     *note locales: Language Environments.

   The rest of this chapter describes these issues in detail.

* Menu:

* International Chars::     Basic concepts of multibyte characters.
* Enabling Multibyte::      Controlling whether to use multibyte characters.
* Language Environments::   Setting things up for the language you use.
* Input Methods::           Entering text characters not on your keyboard.
* Select Input Method::     Specifying your choice of input methods.
* Coding Systems::          Character set conversion when you read and
                              write files, and so on.
* Recognize Coding::        How Emacs figures out which conversion to use.
* Specify Coding::          Specifying a file's coding system explicitly.
* Output Coding::           Choosing coding systems for output.
* Text Coding::             Choosing conversion to use for file text.
* Communication Coding::    Coding systems for interprocess communication.
* File Name Coding::        Coding systems for file _names_.
* Terminal Coding::         Specifying coding systems for converting
                              terminal input and output.
* Fontsets::                Fontsets are collections of fonts
                              that cover the whole spectrum of characters.
* Defining Fontsets::       Defining a new fontset.
* Modifying Fontsets::      Modifying an existing fontset.
* Undisplayable Characters:: When characters don't display.
* Unibyte Mode::            You can pick one European character set
                              to use without multibyte characters.
* Charsets::                How Emacs groups its internal character codes.


File: emacs,  Node: International Chars,  Next: Enabling Multibyte,  Up: International

26.1 Introduction to International Character Sets
=================================================

The users of international character sets and scripts have established
many more-or-less standard coding systems for storing files.  These
coding systems are typically "multibyte", meaning that sequences of two
or more bytes are used to represent individual non-ASCII characters.

   Internally, Emacs uses its own multibyte character encoding, which
is a superset of the "Unicode" standard.  This internal encoding allows
characters from almost every known script to be intermixed in a single
buffer or string.  Emacs translates between the multibyte character
encoding and various other coding systems when reading and writing
files, and when exchanging data with subprocesses.

   The command `C-h h' (`view-hello-file') displays the file
`etc/HELLO', which shows how to say "hello" in many languages.  This
illustrates various scripts.  If some characters can't be displayed on
your terminal, they appear as `?' or as hollow boxes (*note
Undisplayable Characters::).

   Keyboards, even in the countries where these character sets are
used, generally don't have keys for all the characters in them.  You
can insert characters that your keyboard does not support, using `C-q'
(`quoted-insert') or `C-x 8 <RET>' (`ucs-insert').  *Note Inserting
Text::.  Emacs also supports various "input methods", typically one for
each script or language, which make it easier to type characters in the
script.  *Note Input Methods::.

   The prefix key `C-x <RET>' is used for commands that pertain to
multibyte characters, coding systems, and input methods.

   The command `C-x =' (`what-cursor-position') shows information about
the character at point.  In addition to the character position, which
was described in *note Position Info::, this command displays how the
character is encoded.  For instance, it displays the following line in
the echo area for the character `c':

     Char: c (99, #o143, #x63) point=28062 of 36168 (78%) column=53

   The four values after `Char:' describe the character that follows
point, first by showing it and then by giving its character code in
decimal, octal and hex.  For a non-ASCII multibyte character, these are
followed by `file' and the character's representation, in hex, in the
buffer's coding system, if that coding system encodes the character
safely and with a single byte (*note Coding Systems::).  If the
character's encoding is longer than one byte, Emacs shows `file ...'.

   As a special case, if the character lies in the range 128 (0200
octal) through 159 (0237 octal), it stands for a "raw" byte that does
not correspond to any specific displayable character.  Such a
"character" lies within the `eight-bit-control' character set, and is
displayed as an escaped octal character code.  In this case, `C-x ='
shows `part of display ...' instead of `file'.

   With a prefix argument (`C-u C-x ='), this command displays a
detailed description of the character in a window:

   * The character set name, and the codes that identify the character
     within that character set; ASCII characters are identified as
     belonging to the `ascii' character set.

   * The character's syntax and categories.

   * The character's encodings, both internally in the buffer, and
     externally if you were to save the file.

   * What keys to type to input the character in the current input
     method (if it supports the character).

   * If you are running Emacs on a graphical display, the font name and
     glyph code for the character.  If you are running Emacs on a
     text-only terminal, the code(s) sent to the terminal.

   * The character's text properties (*note Text Properties:
     (elisp)Text Properties.), including any non-default faces used to
     display the character, and any overlays containing it (*note
     Overlays: (elisp)Overlays.).

   Here's an example showing the Latin-1 character A with grave accent,
in a buffer whose coding system is `utf-8-unix':

             character: A` (192, #o300, #xc0)
     preferred charset: unicode (Unicode (ISO10646))
            code point: 0xC0
                syntax: w    which means: word
              category: j:Japanese l:Latin v:Vietnamese
           buffer code: #xC3 #x80
             file code: not encodable by coding system undecided-unix
               display: by this font (glyph code)
         xft:-unknown-DejaVu Sans Mono-normal-normal-
             normal-*-13-*-*-*-m-0-iso10646-1 (#x82)

     Character code properties: customize what to show
       name: LATIN CAPITAL LETTER A WITH GRAVE
       general-category: Lu (Letter, Uppercase)
       decomposition: (65 768) ('A' '̀')
       old-name: LATIN CAPITAL LETTER A GRAVE

     There are text properties here:
       auto-composed        t


File: emacs,  Node: Enabling Multibyte,  Next: Language Environments,  Prev: International Chars,  Up: International

26.2 Enabling Multibyte Characters
==================================

By default, Emacs starts in multibyte mode: it stores the contents of
buffers and strings using an internal encoding that represents
non-ASCII characters using multi-byte sequences.  Multibyte mode allows
you to use all the supported languages and scripts without limitations.

   Under very special circumstances, you may want to disable multibyte
character support, for a specific buffer.  When multibyte characters
are disabled in a buffer, we call that "unibyte mode".  In unibyte
mode, each character in the buffer has a character code ranging from 0
through 255 (0377 octal); 0 through 127 (0177 octal) represent ASCII
characters, and 128 (0200 octal) through 255 (0377 octal) represent
non-ASCII characters.

   To edit a particular file in unibyte representation, visit it using
`find-file-literally'.  *Note Visiting::.  You can convert a multibyte
buffer to unibyte by saving it to a file, killing the buffer, and
visiting the file again with `find-file-literally'.  Alternatively, you
can use `C-x <RET> c' (`universal-coding-system-argument') and specify
`raw-text' as the coding system with which to visit or save a file.
*Note Text Coding::.  Unlike `find-file-literally', finding a file as
`raw-text' doesn't disable format conversion, uncompression, or auto
mode selection.

   Emacs normally loads Lisp files as multibyte.  This includes the
Emacs initialization file, `.emacs', and the initialization files of
Emacs packages such as Gnus.  However, you can specify unibyte loading
for a particular Lisp file, by putting `-*-unibyte: t;-*-' in a comment
on the first line (*note File Variables::).  Then that file is always
loaded as unibyte text.  The motivation for these conventions is that
it is more reliable to always load any particular Lisp file in the same
way.  However, you can load a Lisp file as unibyte, on any one
occasion, by typing `C-x <RET> c raw-text <RET>' immediately before
loading it.

   The mode line indicates whether multibyte character support is
enabled in the current buffer.  If it is, there are two or more
characters (most often two dashes) near the beginning of the mode line,
before the indication of the visited file's end-of-line convention
(colon, backslash, etc.).  When multibyte characters are not enabled,
nothing precedes the colon except a single dash.  *Note Mode Line::,
for more details about this.

   You can turn on multibyte support in a specific buffer by invoking
the command `toggle-enable-multibyte-characters' in that buffer.


File: emacs,  Node: Language Environments,  Next: Input Methods,  Prev: Enabling Multibyte,  Up: International

26.3 Language Environments
==========================

All supported character sets are supported in Emacs buffers whenever
multibyte characters are enabled; there is no need to select a
particular language in order to display its characters in an Emacs
buffer.  However, it is important to select a "language environment" in
order to set various defaults.  Roughly speaking, the language
environment represents a choice of preferred script rather than a
choice of language.

   The language environment controls which coding systems to recognize
when reading text (*note Recognize Coding::).  This applies to files,
incoming mail, and any other text you read into Emacs.  It may also
specify the default coding system to use when you create a file.  Each
language environment also specifies a default input method.

   To select a language environment, customize
`current-language-environment' or use the command `M-x
set-language-environment'.  It makes no difference which buffer is
current when you use this command, because the effects apply globally
to the Emacs session.  The supported language environments include:

     ASCII, Belarusian, Bengali, Brazilian Portuguese, Bulgarian,
     Chinese-BIG5, Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Chinese-GBK,
     Chinese-GB18030, Croatian, Cyrillic-ALT, Cyrillic-ISO,
     Cyrillic-KOI8, Czech, Devanagari, Dutch, English, Esperanto,
     Ethiopic, French, Georgian, German, Greek, Gujarati, Hebrew, IPA,
     Italian, Japanese, Kannada, Khmer, Korean, Lao, Latin-1, Latin-2,
     Latin-3, Latin-4, Latin-5, Latin-6, Latin-7, Latin-8 (Celtic),
     Latin-9 (updated Latin-1 with the Euro sign), Latvian, Lithuanian,
     Malayalam, Oriya, Polish, Punjabi, Romanian, Russian, Sinhala,
     Slovak, Slovenian, Spanish, Swedish, TaiViet, Tajik, Tamil,
     Telugu, Thai, Tibetan, Turkish, UTF-8 (for a setup which prefers
     Unicode characters and files encoded in UTF-8), Ukrainian,
     Vietnamese, Welsh, and Windows-1255 (for a setup which prefers
     Cyrillic characters and files encoded in Windows-1255).

   To display the script(s) used by your language environment on a
graphical display, you need to have a suitable font.  If some of the
characters appear as empty boxes, you should install the GNU Intlfonts
package, which includes fonts for most supported scripts.(1) *Note
Fontsets::, for more details about setting up your fonts.

   Some operating systems let you specify the character-set locale you
are using by setting the locale environment variables `LC_ALL',
`LC_CTYPE', or `LANG'.(2)  During startup, Emacs looks up your
character-set locale's name in the system locale alias table, matches
its canonical name against entries in the value of the variables
`locale-charset-language-names' and `locale-language-names', and
selects the corresponding language environment if a match is found.
(The former variable overrides the latter.)  It also adjusts the display
table and terminal coding system, the locale coding system, the
preferred coding system as needed for the locale, and--last but not
least--the way Emacs decodes non-ASCII characters sent by your keyboard.

   If you modify the `LC_ALL', `LC_CTYPE', or `LANG' environment
variables while running Emacs, you may want to invoke the
`set-locale-environment' function afterwards to readjust the language
environment from the new locale.

   The `set-locale-environment' function normally uses the preferred
coding system established by the language environment to decode system
messages.  But if your locale matches an entry in the variable
`locale-preferred-coding-systems', Emacs uses the corresponding coding
system instead.  For example, if the locale `ja_JP.PCK' matches
`japanese-shift-jis' in `locale-preferred-coding-systems', Emacs uses
that encoding even though it might normally use `japanese-iso-8bit'.

   You can override the language environment chosen at startup with
explicit use of the command `set-language-environment', or with
customization of `current-language-environment' in your init file.

   To display information about the effects of a certain language
environment LANG-ENV, use the command `C-h L LANG-ENV <RET>'
(`describe-language-environment').  This tells you which languages this
language environment is useful for, and lists the character sets,
coding systems, and input methods that go with it.  It also shows some
sample text to illustrate scripts used in this language environment.
If you give an empty input for LANG-ENV, this command describes the
chosen language environment.    You can customize any language
environment with the normal hook `set-language-environment-hook'.  The
command `set-language-environment' runs that hook after setting up the
new language environment.  The hook functions can test for a specific
language environment by checking the variable
`current-language-environment'.  This hook is where you should put
non-default settings for specific language environment, such as coding
systems for keyboard input and terminal output, the default input
method, etc.

   Before it starts to set up the new language environment,
`set-language-environment' first runs the hook
`exit-language-environment-hook'.  This hook is useful for undoing
customizations that were made with `set-language-environment-hook'.
For instance, if you set up a special key binding in a specific language
environment using `set-language-environment-hook', you should set up
`exit-language-environment-hook' to restore the normal binding for that
key.

   ---------- Footnotes ----------

   (1) If you run Emacs on X, you need to inform the X server about the
location of the newly installed fonts with the following commands:

      xset fp+ /usr/local/share/emacs/fonts
      xset fp rehash

   (2) If more than one of these is set, the first one that is nonempty
specifies your locale for this purpose.


File: emacs,  Node: Input Methods,  Next: Select Input Method,  Prev: Language Environments,  Up: International

26.4 Input Methods
==================

An "input method" is a kind of character conversion designed
specifically for interactive input.  In Emacs, typically each language
has its own input method; sometimes several languages which use the same
characters can share one input method.  A few languages support several
input methods.

   The simplest kind of input method works by mapping ASCII letters
into another alphabet; this allows you to use one other alphabet
instead of ASCII.  The Greek and Russian input methods work this way.

   A more powerful technique is composition: converting sequences of
characters into one letter.  Many European input methods use composition
to produce a single non-ASCII letter from a sequence that consists of a
letter followed by accent characters (or vice versa).  For example, some
methods convert the sequence `a'' into a single accented letter.  These
input methods have no special commands of their own; all they do is
compose sequences of printing characters.

   The input methods for syllabic scripts typically use mapping followed
by composition.  The input methods for Thai and Korean work this way.
First, letters are mapped into symbols for particular sounds or tone
marks; then, sequences of these which make up a whole syllable are
mapped into one syllable sign.

   Chinese and Japanese require more complex methods.  In Chinese input
methods, first you enter the phonetic spelling of a Chinese word (in
input method `chinese-py', among others), or a sequence of portions of
the character (input methods `chinese-4corner' and `chinese-sw', and
others).  One input sequence typically corresponds to many possible
Chinese characters.  You select the one you mean using keys such as
`C-f', `C-b', `C-n', `C-p', and digits, which have special meanings in
this situation.

   The possible characters are conceptually arranged in several rows,
with each row holding up to 10 alternatives.  Normally, Emacs displays
just one row at a time, in the echo area; `(I/J)' appears at the
beginning, to indicate that this is the Ith row out of a total of J
rows.  Type `C-n' or `C-p' to display the next row or the previous row.

   Type `C-f' and `C-b' to move forward and backward among the
alternatives in the current row.  As you do this, Emacs highlights the
current alternative with a special color; type `C-<SPC>' to select the
current alternative and use it as input.  The alternatives in the row
are also numbered; the number appears before the alternative.  Typing a
digit N selects the Nth alternative of the current row and uses it as
input.

   <TAB> in these Chinese input methods displays a buffer showing all
the possible characters at once; then clicking `Mouse-2' on one of them
selects that alternative.  The keys `C-f', `C-b', `C-n', `C-p', and
digits continue to work as usual, but they do the highlighting in the
buffer showing the possible characters, rather than in the echo area.

   In Japanese input methods, first you input a whole word using
phonetic spelling; then, after the word is in the buffer, Emacs
converts it into one or more characters using a large dictionary.  One
phonetic spelling corresponds to a number of different Japanese words;
to select one of them, use `C-n' and `C-p' to cycle through the
alternatives.

   Sometimes it is useful to cut off input method processing so that the
characters you have just entered will not combine with subsequent
characters.  For example, in input method `latin-1-postfix', the
sequence `e '' combines to form an `e' with an accent.  What if you
want to enter them as separate characters?

   One way is to type the accent twice; this is a special feature for
entering the separate letter and accent.  For example, `e ' '' gives
you the two characters `e''.  Another way is to type another letter
after the `e'--something that won't combine with that--and immediately
delete it.  For example, you could type `e e <DEL> '' to get separate
`e' and `''.

   Another method, more general but not quite as easy to type, is to use
`C-\ C-\' between two characters to stop them from combining.  This is
the command `C-\' (`toggle-input-method') used twice.  *Note Select
Input Method::.

   `C-\ C-\' is especially useful inside an incremental search, because
it stops waiting for more characters to combine, and starts searching
for what you have already entered.

   To find out how to input the character after point using the current
input method, type `C-u C-x ='.  *Note Position Info::.

   The variables `input-method-highlight-flag' and
`input-method-verbose-flag' control how input methods explain what is
happening.  If `input-method-highlight-flag' is non-`nil', the partial
sequence is highlighted in the buffer (for most input methods--some
disable this feature).  If `input-method-verbose-flag' is non-`nil',
the list of possible characters to type next is displayed in the echo
area (but not when you are in the minibuffer).

   Another facility for typing characters not on your keyboard is by
using the `C-x 8 <RET>' (`ucs-insert') to insert a single character
based on its Unicode name or code-point; see *note Inserting Text::.


File: emacs,  Node: Select Input Method,  Next: Coding Systems,  Prev: Input Methods,  Up: International

26.5 Selecting an Input Method
==============================

`C-\'
     Enable or disable use of the selected input method.

`C-x <RET> C-\ METHOD <RET>'
     Select a new input method for the current buffer.

`C-h I METHOD <RET>'
`C-h C-\ METHOD <RET>'
     Describe the input method METHOD (`describe-input-method').  By
     default, it describes the current input method (if any).  This
     description should give you the full details of how to use any
     particular input method.

`M-x list-input-methods'
     Display a list of all the supported input methods.

   To choose an input method for the current buffer, use `C-x <RET>
C-\' (`set-input-method').  This command reads the input method name
from the minibuffer; the name normally starts with the language
environment that it is meant to be used with.  The variable
`current-input-method' records which input method is selected.

   Input methods use various sequences of ASCII characters to stand for
non-ASCII characters.  Sometimes it is useful to turn off the input
method temporarily.  To do this, type `C-\' (`toggle-input-method').
To reenable the input method, type `C-\' again.

   If you type `C-\' and you have not yet selected an input method, it
prompts for you to specify one.  This has the same effect as using `C-x
<RET> C-\' to specify an input method.

   When invoked with a numeric argument, as in `C-u C-\',
`toggle-input-method' always prompts you for an input method,
suggesting the most recently selected one as the default.

   Selecting a language environment specifies a default input method for
use in various buffers.  When you have a default input method, you can
select it in the current buffer by typing `C-\'.  The variable
`default-input-method' specifies the default input method (`nil' means
there is none).

   In some language environments, which support several different input
methods, you might want to use an input method different from the
default chosen by `set-language-environment'.  You can instruct Emacs
to select a different default input method for a certain language
environment, if you wish, by using `set-language-environment-hook'
(*note set-language-environment-hook: Language Environments.).  For
example:

     (defun my-chinese-setup ()
       "Set up my private Chinese environment."
       (if (equal current-language-environment "Chinese-GB")
           (setq default-input-method "chinese-tonepy")))
     (add-hook 'set-language-environment-hook 'my-chinese-setup)

This sets the default input method to be `chinese-tonepy' whenever you
choose a Chinese-GB language environment.

   You can instruct Emacs to activate a certain input method
automatically.  For example:

     (add-hook 'text-mode-hook
       (lambda () (set-input-method "german-prefix")))

This activates the input method "german-prefix" automatically in the
Text mode.

   Some input methods for alphabetic scripts work by (in effect)
remapping the keyboard to emulate various keyboard layouts commonly used
for those scripts.  How to do this remapping properly depends on your
actual keyboard layout.  To specify which layout your keyboard has, use
the command `M-x quail-set-keyboard-layout'.

   You can use the command `M-x quail-show-key' to show what key (or
key sequence) to type in order to input the character following point,
using the selected keyboard layout.  The command `C-u C-x =' also shows
that information in addition to the other information about the
character.

   `M-x list-input-methods' displays a list of all the supported input
methods.  The list gives information about each input method, including
the string that stands for it in the mode line.

