This commit was manufactured by cvs2svn to create branch 'utf-2000'.

[chise/xemacs-chise.git-] / info / xemacs.info-6

This is ../info/xemacs.info, produced by makeinfo version 4.0 from
xemacs/xemacs.texi.

INFO-DIR-SECTION XEmacs Editor
START-INFO-DIR-ENTRY
* XEmacs: (xemacs).             XEmacs Editor.
END-INFO-DIR-ENTRY

   This file documents the XEmacs editor.

   Copyright (C) 1985, 1986, 1988 Richard M. Stallman.  Copyright (C)
1991, 1992, 1993, 1994 Lucid, Inc.  Copyright (C) 1993, 1994 Sun
Microsystems, Inc.  Copyright (C) 1995 Amdahl Corporation.

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

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

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

\1f
File: xemacs.info,  Node: Scrolling,  Next: Horizontal Scrolling,  Prev: Display,  Up: Display

Scrolling
=========

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

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

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

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

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

`M-v'
`pgup'
`prior'
     Scroll backward (`scroll-down').

`ARG C-l'
     Scroll so point is on line ARG (`recenter').

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

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

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

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

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

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

   If you set `scroll-step' to a small value because you want to use
arrow keys to scroll the screen without recentering, the redisplay
preemption will likely make XEmacs keep recentering the screen when
scrolling fast, regardless of `scroll-step'.  To prevent this, set
`scroll-conservatively' to a small value, which will have the result of
overriding the redisplay preemption.

\1f
File: xemacs.info,  Node: Horizontal Scrolling,  Prev: Scrolling,  Up: Display

Horizontal Scrolling
====================

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

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

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

   The command `C-x <' (`scroll-left') scrolls the selected window to
the left by N columns with argument N.  With no argument, it scrolls by
almost the full width of the window (two columns less, to be precise).
`C-x >' (`scroll-right') scrolls similarly to the right.  The window
cannot be scrolled any farther to the right once it is displaying
normally (with each line starting at the window's left margin);
attempting to do so has no effect.

\1f
File: xemacs.info,  Node: Selective Display,  Next: Display Vars,  Prev: Display,  Up: Display

Selective Display
=================

   XEmacs can hide lines indented more than a certain number of columns
(you specify how many columns).  This allows you  to get an overview of
a part of a program.

   To hide lines, type `C-x $' (`set-selective-display') with a numeric
argument N.  (*Note Arguments::, for information on giving the
argument.)  Lines with at least N columns of indentation disappear from
the screen.  The only indication of their presence are three dots
(`...'), which appear at the end of each visible line that is followed
by one or more invisible ones.

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

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

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

\1f
File: xemacs.info,  Node: Display Vars,  Prev: Selective Display,  Up: Display

Variables Controlling Display
=============================

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

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

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

   If the variable `ctl-arrow' is `nil', control characters in the
buffer are displayed with octal escape sequences, all except newline and
tab.  If its value is `t', then control characters will be printed with
an up-arrow, for example `^A'.

   If its value is not `t' and not `nil', then characters whose code is
greater than 160 (that is, the space character (32) with its high bit
set) will be assumed to be printable, and will be displayed without
alteration.  This is the default when running under X Windows, since
XEmacs assumes an ISO/8859-1 character set (also known as "Latin1").
The `ctl-arrow' variable may also be set to an integer, in which case
all characters whose codes are greater than or equal to that value will
be assumed to be printable.

   Altering the value of `ctl-arrow' makes it local to the current
buffer; until that time, the default value is in effect.  *Note
Locals::.

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

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

\1f
File: xemacs.info,  Node: Search,  Next: Fixit,  Prev: Display,  Up: Top

Searching and Replacement
*************************

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

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

* Menu:

* Incremental Search::     Search happens as you type the string.
* Non-Incremental Search:: Specify entire string and then search.
* Word Search::            Search for sequence of words.
* Regexp Search::          Search for match for a regexp.
* Regexps::                Syntax of regular expressions.
* Search Case::            To ignore case while searching, or not.
* Replace::                Search, and replace some or all matches.
* Other Repeating Search:: Operating on all matches for some regexp.

\1f
File: xemacs.info,  Node: Incremental Search,  Next: Non-Incremental Search,  Prev: Search,  Up: Search

Incremental Search
==================

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

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

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

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

   The echo area display ends with three dots when actual searching is
going on.  When search is waiting for more input, the three dots are
removed.  (On slow terminals, the three dots are not displayed.)

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

   When you are satisfied with the place you have reached, you can type
<RET> (or <C-m>), which stops searching, leaving the cursor where the
search brought it.  Any command not specially meaningful in searches
also stops the search and is then executed.  Thus, typing `C-a' exits
the search and then moves to the beginning of the line.  <RET> is
necessary only if the next command you want to type is a printing
character, <DEL>, <ESC>, or another control character that is special
within searches (`C-q', `C-w', `C-r', `C-s', or `C-y').

   Sometimes you search for `FOO' and find it, but were actually
looking for a different occurrence of it.  To move to the next
occurrence of the search string, type another `C-s'.  Do this as often
as necessary.  If you overshoot, you can cancel some `C-s' characters
with <DEL>.

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

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

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

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

   To search for a control character such as `C-s' or <DEL> or <ESC>,
you must quote it by typing `C-q' first.  This function of `C-q' is
analogous to its meaning as an Emacs command: it causes the following
character to be treated the way a graphic character would normally be
treated in the same context.

   To search backwards, you can use `C-r' instead of `C-s' to start the
search; `C-r' is the key that runs the command (`isearch-backward') to
search backward.  You can also use `C-r' to change from searching
forward to searching backwards.  Do this if a search fails because the
place you started was too far down in the file.  Repeated `C-r' keeps
looking for more occurrences backwards.  `C-s' starts going forward
again.  You can cancel `C-r' in a search with <DEL>.

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

   The characters `M-p' and `M-n' can be used in an incremental search
to recall things which you have searched for in the past.  A list of
the last 16 things you have searched for is retained, and `M-p' and
`M-n' let you cycle through that ring.

   The character `M-<TAB>' does completion on the elements in the
search history ring.  For example, if you know that you have recently
searched for the string `POTATOE', you could type `C-s P O M-<TAB>'.
If you had searched for other strings beginning with `PO' then you
would be shown a list of them, and would need to type more to select
one.

   You can change any of the special characters in incremental search
via the normal keybinding mechanism: simply add a binding to the
`isearch-mode-map'.  For example, to make the character `C-b' mean
"search backwards" while in isearch-mode, do this:

     (define-key isearch-mode-map "\C-b" 'isearch-repeat-backward)

   These are the default bindings of isearch-mode:

`DEL'
     Delete a character from the incremental search string
     (`isearch-delete-char').

`RET'
     Exit incremental search (`isearch-exit').

`C-q'
     Quote special characters for incremental search
     (`isearch-quote-char').

`C-s'
     Repeat incremental search forward (`isearch-repeat-forward').

`C-r'
     Repeat incremental search backward (`isearch-repeat-backward').

`C-y'
     Pull rest of line from buffer into search string
     (`isearch-yank-line').

`C-w'
     Pull next word from buffer into search string
     (`isearch-yank-word').

`C-g'
     Cancels input back to what has been found successfully, or aborts
     the isearch (`isearch-abort').

`M-p'
     Recall the previous element in the isearch history ring
     (`isearch-ring-retreat').

`M-n'
     Recall the next element in the isearch history ring
     (`isearch-ring-advance').

`M-<TAB>'
     Do completion on the elements in the isearch history ring
     (`isearch-complete').

   Any other character which is normally inserted into a buffer when
typed is automatically added to the search string in isearch-mode.

Slow Terminal Incremental Search
--------------------------------

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

   When the search is terminated, the single-line window is removed.
Only at this time the window in which the search was done is
redisplayed to show its new value of point.

   The three dots at the end of the search string, normally used to
indicate that searching is going on, are not displayed in slow style
display.

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

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

\1f
File: xemacs.info,  Node: Non-Incremental Search,  Next: Word Search,  Prev: Incremental Search,  Up: Search

Non-Incremental Search
======================

   Emacs also has conventional non-incremental search commands, which
require you type the entire search string before searching begins.

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

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

   To do a non-incremental search, first type `C-s <RET>' (or `C-s
C-m').  This enters the minibuffer to read the search string.
Terminate the string with <RET> to start the search.  If the string is
not found, the search command gets an error.

   By default, `C-s' invokes incremental search, but if you give it an
empty argument, which would otherwise be useless, it invokes
non-incremental search.  Therefore, `C-s <RET>' invokes non-incremental
search.  `C-r <RET>' also works this way.

   Forward and backward non-incremental searches are implemented by the
commands `search-forward' and `search-backward'.  You can bind these
commands to keys.  The reason that incremental search is programmed to
invoke them as well is that `C-s <RET>' is the traditional sequence of
characters used in Emacs to invoke non-incremental search.

   Non-incremental searches performed using `C-s <RET>' do not call
`search-forward' right away.  They first check if the next character is
`C-w', which requests a word search.  *Note Word Search::.

\1f
File: xemacs.info,  Node: Word Search,  Next: Regexp Search,  Prev: Non-Incremental Search,  Up: Search

Word Search
===========

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

   Word search is useful in editing documents formatted by text
formatters.  If you edit while looking at the printed, formatted
version, you can't tell where the line breaks are in the source file.
Word search, allows you to search  without having to know the line
breaks.

`C-s <RET> C-w WORDS <RET>'
     Search for WORDS, ignoring differences in punctuation.

`C-r <RET> C-w WORDS <RET>'
     Search backward for WORDS, ignoring differences in punctuation.

   Word search is a special case of non-incremental search.  It is
invoked with `C-s <RET> C-w' followed by the search string, which must
always be terminated with another <RET>.  Being non-incremental, this
search does not start until the argument is terminated.  It works by
constructing a regular expression and searching for that.  *Note Regexp
Search::.

   You can do a backward word search with `C-r <RET> C-w'.

   Forward and backward word searches are implemented by the commands
`word-search-forward' and `word-search-backward'.  You can bind these
commands to keys.  The reason that incremental search is programmed to
invoke them as well is that `C-s <RET> C-w' is the traditional Emacs
sequence of keys for word search.

\1f
File: xemacs.info,  Node: Regexp Search,  Next: Regexps,  Prev: Word Search,  Up: Search

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

   A "regular expression" ("regexp", for short) is a pattern that
denotes a (possibly infinite) set of strings.  Searching for matches
for a regexp is a powerful operation that editors on Unix systems have
traditionally offered.

   To gain a thorough understanding of regular expressions and how to
use them to best advantage, we recommend that you study `Mastering
Regular Expressions, by Jeffrey E.F. Friedl, O'Reilly and Associates,
1997'. (It's known as the "Hip Owls" book, because of the picture on its
cover.)  You might also read the manuals to *Note (gawk)Top::, *Note
(ed)Top::, `sed', `grep', *Note (perl)Top::, *Note (regex)Top::, *Note
(rx)Top::, `pcre', and *Note (flex)Top::, which also make good use of
regular expressions.

   The XEmacs regular expression syntax most closely resembles that of
`ed', or `grep', the GNU versions of which all utilize the GNU `regex'
library.  XEmacs' version of `regex' has recently been extended with
some Perl-like capabilities, described in the next section.

   In XEmacs, you can search for the next match for a regexp either
incrementally or not.

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

   All of the control characters that do special things within an
ordinary incremental search have the same functionality in incremental
regexp search.  Typing `C-s' or `C-r' immediately after starting a
search retrieves the last incremental search regexp used: incremental
regexp and non-regexp searches have independent defaults.

   Non-incremental search for a regexp is done by the functions
`re-search-forward' and `re-search-backward'.  You can invoke them with
`M-x' or bind them to keys.  You can also call `re-search-forward' by
way of incremental regexp search with `M-C-s <RET>'; similarly for
`re-search-backward' with `M-C-r <RET>'.

\1f
File: xemacs.info,  Node: Regexps,  Next: Search Case,  Prev: Regexp Search,  Up: Search

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

   Regular expressions have a syntax in which a few characters are
special constructs and the rest are "ordinary".  An ordinary character
is a simple regular expression that matches that character and nothing
else.  The special characters are `.', `*', `+', `?', `[', `]', `^',
`$', and `\'; no new special characters will be defined in the future.
Any other character appearing in a regular expression is ordinary,
unless a `\' precedes it.

   For example, `f' is not a special character, so it is ordinary, and
therefore `f' is a regular expression that matches the string `f' and
no other string.  (It does _not_ match the string `ff'.)  Likewise, `o'
is a regular expression that matches only `o'.

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

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

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

`*'
     is not a construct by itself; it is a quantifying suffix operator
     that means to repeat the preceding regular expression as many
     times as possible.  In `fo*', the `*' applies to the `o', so `fo*'
     matches one `f' followed by any number of `o's.  The case of zero
     `o's is allowed: `fo*' does match `f'.

     `*' always applies to the _smallest_ possible preceding
     expression.  Thus, `fo*' has a repeating `o', not a repeating `fo'.

     The matcher processes a `*' construct by matching, immediately, as
     many repetitions as can be found; it is "greedy".  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.

     Nested repetition operators can be extremely slow if they specify
     backtracking loops.  For example, it could take hours for the
     regular expression `\(x+y*\)*a' to match the sequence
     `xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz'.  The slowness is because
     Emacs must try each imaginable way of grouping the 35 `x''s before
     concluding that none of them can work.  To make sure your regular
     expressions run fast, check nested repetitions carefully.

`+'
     is a quantifying suffix operator similar to `*' except that the
     preceding expression must match at least once.  It is also
     "greedy".  So, for example, `ca+r' matches the strings `car' and
     `caaaar' but not the string `cr', whereas `ca*r' matches all three
     strings.

`?'
     is a quantifying suffix operator similar to `*', except that the
     preceding expression can match either once or not at all.  For
     example, `ca?r' matches `car' or `cr', but does not match anything
     else.

`*?'
     works just like `*', except that rather than matching the longest
     match, it matches the shortest match.  `*?' is known as a
     "non-greedy" quantifier, a regexp construct borrowed from Perl.

     This construct is very useful for when you want to match the text
     inside a pair of delimiters.  For instance, `/\*.*?\*/' will match
     C comments in a string.  This could not easily be achieved without
     the use of a non-greedy quantifier.

     This construct has not been available prior to XEmacs 20.4.  It is
     not available in FSF Emacs.

`+?'
     is the non-greedy version of `+'.

`??'
     is the non-greedy version of `?'.

`\{n,m\}'
     serves as an interval quantifier, analogous to `*' or `+', but
     specifies that the expression must match at least N times, but no
     more than M times.  This syntax is supported by most Unix regexp
     utilities, and has been introduced to XEmacs for the version 20.3.

     Unfortunately, the non-greedy version of this quantifier does not
     exist currently, although it does in Perl.

`[ ... ]'
     `[' begins a "character set", which is terminated by a `]'.  In
     the simplest case, the characters between the two brackets form
     the set.  Thus, `[ad]' matches either one `a' or one `d', and
     `[ad]*' matches any string composed of just `a's and `d's
     (including the empty string), from which it follows that `c[ad]*r'
     matches `cr', `car', `cdr', `caddaar', etc.

     The usual regular expression special characters are not special
     inside a character set.  A completely different set of special
     characters exists inside character sets: `]', `-' and `^'.

     `-' is used for ranges of characters.  To write a range, write two
     characters with a `-' between them.  Thus, `[a-z]' matches any
     lower case letter.  Ranges may be intermixed freely with individual
     characters, as in `[a-z$%.]', which matches any lower case letter
     or `$', `%', or a period.

     To include a `]' in a character set, make it the first character.
     For example, `[]a]' matches `]' or `a'.  To include a `-', write
     `-' as the first character in the set, or put it immediately after
     a range.  (You can replace one individual character C with the
     range `C-C' to make a place to put the `-'.)  There is no way to
     write a set containing just `-' and `]'.

     To include `^' in a set, put it anywhere but at the beginning of
     the set.

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

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

     Note that a complement character set can match a newline, unless
     newline is mentioned as one of the characters not to match.

`^'
     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.

     When matching a string instead of a buffer, `^' matches at the
     beginning of the string or after a newline character `\n'.

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

     When matching a string instead of a buffer, `$' matches at the end
     of the string or before a newline character `\n'.

`\'
     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.

   *Please 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; quote the special character
anyway, regardless of where it appears.

   For the most part, `\' followed by any character matches only that
character.  However, there are several exceptions: characters that,
when preceded by `\', are special constructs.  Such characters are
always ordinary when encountered on their own.  Here is a table of `\'
constructs:

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

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

     `\|' applies to the largest possible surrounding expressions.
     Only a surrounding `\( ... \)' grouping can limit the 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 an expression for a suffix operator such as `*' to
          act 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 happens to be
     assigned as a second meaning to the same `\( ... \)' construct
     because there is no conflict in practice between the two meanings.
     Here is an explanation of this feature:

`\DIGIT'
     matches the same text that matched the DIGITth occurrence of a `\(
     ... \)' construct.

     In other words, 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 DIGIT to match that same text, whatever it may
     have been.

     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.

`\(?: ... \)'
     is called a "shy" grouping operator, and it is used just like `\(
     ... \)', except that it does not cause the matched substring to be
     recorded for future reference.

     This is useful when you need a lot of grouping `\( ... \)'
     constructs, but only want to remember one or two - or if you have
     more than nine groupings and need to use backreferences to refer to
     the groupings at the end.

     Using `\(?: ... \)' rather than `\( ... \)' when you don't need
     the captured substrings ought to speed up your programs some,
     since it shortens the code path followed by the regular expression
     engine, as well as the amount of memory allocation and string
     copying it must do.  The actual performance gain to be observed
     has not been measured or quantified as of this writing.

     The shy grouping operator has been borrowed from Perl, and has not
     been available prior to XEmacs 20.3, nor is it available in FSF
     Emacs.

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

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

`\sCODE'
     matches any character whose syntax is CODE.  Here CODE is a
     character that represents a syntax code: thus, `w' for word
     constituent, `-' for whitespace, `(' for open parenthesis, etc.
     *Note Syntax::, for a list of syntax codes and the characters that
     stand for them.

`\SCODE'
     matches any character whose syntax is not CODE.

   The following regular expression constructs match the empty
string--that is, they don't use up any characters--but whether they
match depends on the context.

`\`'
     matches the empty string, but only at the beginning of the buffer
     or string being matched against.

`\''
     matches the empty string, but only at the end of the buffer or
     string being matched against.

`\='
     matches the empty string, but only at point.  (This construct is
     not defined when matching against a string.)

`\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 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 the empty string, but only at the end of a word.

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

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

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

\1f
File: xemacs.info,  Node: Search Case,  Next: Replace,  Prev: Regexps,  Up: Search

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

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

   If you want a case-sensitive search, set the variable
`case-fold-search' to `nil'.  Then all letters must match exactly,
including case. `case-fold-search' is a per-buffer variable; altering
it affects only the current buffer, but there is a default value which
you can change as well.  *Note Locals::.  You can also use Case
Sensitive Search from the Options menu on your screen.

\1f
File: xemacs.info,  Node: Replace,  Next: Other Repeating Search,  Prev: Search Case,  Up: Search

Replacement Commands
====================

   Global search-and-replace operations are not needed as often in
Emacs as they are in other editors, but they are available.  In
addition to the simple `replace-string' command which is like that
found in most editors, there is a `query-replace' command which asks
you, for each occurrence of a pattern, whether to replace it.

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

\1f
File: xemacs.info,  Node: Unconditional Replace,  Next: Regexp Replace,  Prev: Replace,  Up: Replace

Unconditional Replacement
-------------------------

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

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

   To replace every instance of `foo' after point with `bar', use the
command `M-x replace-string' with the two arguments `foo' and `bar'.
Replacement occurs only after point: if you want to cover the whole
buffer you must go to the beginning first.  By default, all occurrences
up to the end of the buffer are replaced.  To limit replacement to part
of the buffer, narrow to that part of the buffer before doing the
replacement (*note Narrowing::).

   When `replace-string' exits, point is left at the last occurrence
replaced.  The value of point when the `replace-string' command was
issued is remembered on the mark ring; `C-u C-<SPC>' moves back there.

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

\1f
File: xemacs.info,  Node: Regexp Replace,  Next: Replacement and Case,  Prev: Unconditional Replace,  Up: Replace

Regexp Replacement
------------------

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

   In `replace-regexp', the NEWSTRING need not be constant.  It can
refer to all or part of what is matched by the REGEXP.  `\&' in
NEWSTRING stands for the entire text being replaced.  `\D' in
NEWSTRING, where D is a digit, stands for whatever matched the D'th
parenthesized grouping in REGEXP.  For example,

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

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

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

would perform exactly the opposite replacements.  To include a `\' in
the text to replace with, you must give `\\'.

\1f
File: xemacs.info,  Node: Replacement and Case,  Next: Query Replace,  Prev: Regexp Replace,  Up: Replace

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

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

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

replaces a lower-case `foo' with a lower case `bar', `FOO' with `BAR',
and `Foo' with `Bar'.  If upper-case letters are used in the second
argument, they remain upper-case every time that argument is inserted.
If upper-case letters are used in the first argument, the second
argument is always substituted exactly as given, with no case
conversion.  Likewise, if the variable `case-replace' is set to `nil',
replacement is done without case conversion.  If `case-fold-search' is
set to `nil', case is significant in matching occurrences of `foo' to
replace; also, case conversion of the replacement string is not done.

\1f
File: xemacs.info,  Node: Query Replace,  Prev: Replacement and Case,  Up: Replace

Query Replace
-------------

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

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

   If you want to change only some of the occurrences of `foo' to
`bar', not all of them, you can use `query-replace' instead of `M-%'.
This command finds occurrences of `foo' one by one, displays each
occurrence, and asks you whether to replace it.  A numeric argument to
`query-replace' tells it to consider only occurrences that are bounded
by word-delimiter characters.

   Aside from querying, `query-replace' works just like
`replace-string', and `query-replace-regexp' works just like
`replace-regexp'.

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

`<SPC>'
     to replace the occurrence with NEWSTRING.  This preserves case,
     just like `replace-string', provided `case-replace' is non-`nil',
     as it normally is.

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

`, (Comma)'
     to replace this occurrence and display the result.  You are then
     prompted for another input character.  However, since the
     replacement has already been made, <DEL> and <SPC> are equivalent.
     At this point, you can type `C-r' (see below) to alter the
     replaced text.  To undo the replacement, you can type `C-x u'.
     This exits the `query-replace'.  If you want to do further
     replacement you must use `C-x ESC' to restart (*note Repetition::).

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

`. (Period)'
     to replace this occurrence and then exit.

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

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

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

`C-l'
     to redisplay the screen and then give another answer.

`C-h'
     to display a message summarizing these options, then give another
     answer.

   If you type any other character, Emacs exits the `query-replace', and
executes the character as a command.  To restart the `query-replace',
use `C-x <ESC>', which repeats the `query-replace' because it used the
minibuffer to read its arguments.  *Note C-x ESC: Repetition.

\1f
File: xemacs.info,  Node: Other Repeating Search,  Prev: Replace,  Up: Search

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

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

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

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

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

`M-x count-matches'
     Print the number of matches following point for the specified
     regexp.

`M-x delete-non-matching-lines'
     Delete each line that follows point and does not contain a match
     for the specified regexp.

`M-x delete-matching-lines'
     Delete each line that follows point and contains a match for the
     specified regexp.

\1f
File: xemacs.info,  Node: Fixit,  Next: Files,  Prev: Search,  Up: Top

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

   This chapter describes commands that are especially useful when you
catch a mistake in your text just after you have made it, or when you
change your mind while composing text on line.

* Menu:

* Kill Errors:: Commands to kill a batch of recently entered text.
* 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.

\1f
File: xemacs.info,  Node: Kill Errors,  Next: Transpose,  Prev: Fixit,  Up: Fixit

Killing Your Mistakes
=====================

`<DEL>'
     Delete last character (`delete-backward-char').

`M-<DEL>'
     Kill last word (`backward-kill-word').

`C-x <DEL>'
     Kill to beginning of sentence (`backward-kill-sentence').

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

   When your mistake is longer than a couple of characters, it might be
more convenient to use `M-<DEL>' or `C-x <DEL>'.  `M-<DEL>' kills back
to the start of the last word, and `C-x <DEL>' kills back to the start
of the last sentence.  `C-x <DEL>' is particularly useful when you are
thinking of what to write as you type it, in case you change your mind
about phrasing.  `M-<DEL>' and `C-x <DEL>' save the killed text for
`C-y' and `M-y' to retrieve.  *Note Yanking::.

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