@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2004
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
+@c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/searching
@node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top
@menu
* String Search:: Search for an exact match.
+* Searching and Case:: Case-independent or case-significant searching.
* Regular Expressions:: Describing classes of strings.
* Regexp Search:: Searching for a match for a regexp.
* POSIX Regexps:: Searching POSIX-style for the longest match.
-* Search and Replace:: Internals of @code{query-replace}.
* Match Data:: Finding out which part of the text matched,
after a string or regexp search.
-* Searching and Case:: Case-independent or case-significant searching.
+* Search and Replace:: Commands that loop, searching and replacing.
* Standard Regexps:: Useful regexps for finding sentences, pages,...
@end menu
The @samp{skip-chars@dots{}} functions also perform a kind of searching.
-@xref{Skipping Characters}.
+@xref{Skipping Characters}. To search for changes in character
+properties, see @ref{Property Search}.
@node String Search
@section Searching for Strings
return the new position of point in that case, but some existing
programs may depend on a value of @code{nil}.)
+The argument @var{noerror} only affects valid searches which fail to
+find a match. Invalid arguments cause errors regardless of
+@var{noerror}.
+
If @var{repeat} is supplied (it must be a positive number), then the
search is repeated that many times (each time starting at the end of the
previous time's match). If these successive searches succeed, the
@end group
@end example
-If @var{limit} is non-@code{nil} (it must be a position in the current
-buffer), then it is the upper bound to the search. The match found must
-not extend after that position.
+If @var{limit} is non-@code{nil}, it must be a position in the current
+buffer; it specifies the upper bound to the search. The match found
+must not extend after that position.
If @var{noerror} is @code{nil}, then @code{word-search-forward} signals
an error if the search fails. If @var{noerror} is @code{t}, then it
beginning of the match.
@end deffn
+@node Searching and Case
+@section Searching and Case
+@cindex searching and case
+
+ By default, searches in Emacs ignore the case of the text they are
+searching through; if you specify searching for @samp{FOO}, then
+@samp{Foo} or @samp{foo} is also considered a match. This applies to
+regular expressions, too; thus, @samp{[aB]} would match @samp{a} or
+@samp{A} or @samp{b} or @samp{B}.
+
+ If you do not want this feature, set the variable
+@code{case-fold-search} to @code{nil}. Then all letters must match
+exactly, including case. This is a buffer-local variable; altering the
+variable affects only the current buffer. (@xref{Intro to
+Buffer-Local}.) Alternatively, you may change the value of
+@code{default-case-fold-search}, which is the default value of
+@code{case-fold-search} for buffers that do not override it.
+
+ Note that the user-level incremental search feature handles case
+distinctions differently. When given a lower case letter, it looks for
+a match of either case, but when given an upper case letter, it looks
+for an upper case letter only. But this has nothing to do with the
+searching functions used in Lisp code.
+
+@defopt case-replace
+This variable determines whether the higher level replacement
+functions should preserve case. If the variable is @code{nil}, that
+means to use the replacement text verbatim. A non-@code{nil} value
+means to convert the case of the replacement text according to the
+text being replaced.
+
+This variable is used by passing it as an argument to the function
+@code{replace-match}. @xref{Replacing Match}.
+@end defopt
+
+@defopt case-fold-search
+This buffer-local variable determines whether searches should ignore
+case. If the variable is @code{nil} they do not ignore case; otherwise
+they do ignore case.
+@end defopt
+
+@defvar default-case-fold-search
+The value of this variable is the default value for
+@code{case-fold-search} in buffers that do not override it. This is the
+same as @code{(default-value 'case-fold-search)}.
+@end defvar
+
@node Regular Expressions
@section Regular Expressions
@cindex regular expression
a regexp is a very powerful operation. This section explains how to write
regexps; the following section says how to search for them.
+@findex re-builder
+@cindex authoring regular expressions
+ For convenient interactive development of regular expressions, you
+can use the @kbd{M-x re-builder} command. It provides a convenient
+interface for creating regular expressions, by giving immediate visual
+feedback in a separate buffer. As you edit the regexp, all its
+matches in the target buffer are highlighted. Each parenthesized
+sub-expression of the regexp is shown in a distinct face, which makes
+it easier to verify even very complex regexps.
+
@menu
* Syntax of Regexps:: Rules for writing regular expressions.
* Regexp Example:: Illustrates regular expression syntax.
Regular expressions have a syntax in which a few characters are
special constructs and the rest are @dfn{ordinary}. An ordinary
-character is a simple regular expression that matches that character and
-nothing else. The special characters are @samp{.}, @samp{*}, @samp{+},
-@samp{?}, @samp{[}, @samp{]}, @samp{^}, @samp{$}, and @samp{\}; no new
-special characters will be defined in the future. Any other character
-appearing in a regular expression is ordinary, unless a @samp{\}
-precedes it.
+character is a simple regular expression that matches that character
+and nothing else. The special characters are @samp{.}, @samp{*},
+@samp{+}, @samp{?}, @samp{[}, @samp{^}, @samp{$}, and @samp{\}; no new
+special characters will be defined in the future. The character
+@samp{]} is special if it ends a character alternative (see later).
+The character @samp{-} is special inside a character alternative. A
+@samp{[:} and balancing @samp{:]} enclose a character class inside a
+character alternative. Any other character appearing in a regular
+expression is ordinary, unless a @samp{\} precedes it.
For example, @samp{f} is not a special character, so it is ordinary, and
therefore @samp{f} is a regular expression that matches the string
first tries to match all three @samp{a}s; but the rest of the pattern is
@samp{ar} and there is only @samp{r} left to match, so this try fails.
The next alternative is for @samp{a*} to match only two @samp{a}s. With
-this choice, the rest of the regexp matches successfully.@refill
-
-Nested repetition operators can be extremely slow or loop infinitely
-if they use repetition operators inside repetition operators. For
-example, it could take hours for the regular expression
-@samp{\(x+y*\)*a} to try to match the sequence
-@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}, before it ultimately
-fails. Emacs must try each way of grouping the 35 @samp{x}s before
-concluding that none of them can work. Even worse, @samp{\(x*\)*} can
-match the null string in infinitely many ways, so it causes an
-infinite loop. To avoid these problems, check nested repetitions
-carefully.
+this choice, the rest of the regexp matches successfully.
+
+@strong{Warning:} Nested repetition operators take a long time,
+or even forever, if they
+lead to ambiguous matching. For example, trying to match the regular
+expression @samp{\(x+y*\)*a} against the string
+@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz} could take hours before it
+ultimately fails. Emacs must try each way of grouping the 35
+@samp{x}s before concluding that none of them can work. Even worse,
+@samp{\(x*\)*} can match the null string in infinitely many ways, so
+it causes an infinite loop. To avoid these problems, check nested
+repetitions carefully, to make sure that they do not cause combinatorial
+explosions in backtracking.
@item @samp{+}
@cindex @samp{+} in regexp
in both multibyte and unibyte representations, because only the
@acronym{ASCII} characters are excluded.
-Starting in Emacs 21, a character alternative can also specify named
+A character alternative can also specify named
character classes (@pxref{Char Classes}). This is a POSIX feature whose
syntax is @samp{[:@var{class}:]}. Using a character class is equivalent
to mentioning each of the characters in that class; but the latter is
@item @samp{[^ @dots{} ]}
@cindex @samp{^} in regexp
-@samp{[^} begins a @dfn{complemented character alternative}, which matches any
-character except the ones specified. Thus, @samp{[^a-z0-9A-Z]} matches
-all characters @emph{except} letters and digits.
+@samp{[^} begins a @dfn{complemented character alternative}. This
+matches any character except the ones specified. Thus,
+@samp{[^a-z0-9A-Z]} matches all characters @emph{except} letters and
+digits.
@samp{^} is not special in a character alternative unless it is the first
character. The character following the @samp{^} is treated as if it
beginning of the string or after a newline character.
For historical compatibility reasons, @samp{^} can be used only at the
-beginning of the regular expression, or after @samp{\(} or @samp{\|}.
+beginning of the regular expression, or after @samp{\(}, @samp{\(?:}
+or @samp{\|}.
@item @samp{$}
@cindex @samp{$} in regexp
can act. It is poor practice to depend on this behavior; quote the
special character anyway, regardless of where it appears.@refill
+As a @samp{\} is not special inside a character alternative, it can
+never remove the special meaning of @samp{-} or @samp{]}. 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 @emph{have} special
+meaning, as in @samp{[^\]} (@code{"[^\\]"} for Lisp string syntax),
+which matches any single character except a backslash.
+
+In practice, most @samp{]} that occur in regular expressions close a
+character alternative and hence are special. However, occasionally a
+regular expression may try to match a complex pattern of literal
+@samp{[} and @samp{]}. In such situations, it sometimes may be
+necessary to carefully parse the regexp from the start to determine
+which square brackets enclose a character alternative. For example,
+@samp{[^][]]} consists of the complemented character alternative
+@samp{[^][]} (which matches any single character that is not a square
+bracket), followed by a literal @samp{]}.
+
+The exact rules are that at the beginning of a regexp, @samp{[} is
+special and @samp{]} not. This lasts until the first unquoted
+@samp{[}, after which we are in a character alternative; @samp{[} is
+no longer special (except when it starts a character class) but @samp{]}
+is special, unless it immediately follows the special @samp{[} or that
+@samp{[} followed by a @samp{^}. This lasts until the next special
+@samp{]} that does not end a character class. This ends the character
+alternative and restores the ordinary syntax of regular expressions;
+an unquoted @samp{[} is special again and a @samp{]} not.
+
@node Char Classes
@subsubsection Character Classes
@cindex character classes in regexp
Here is a table of the classes you can use in a character alternative,
-in Emacs 21, and what they mean:
+and what they mean:
@table @samp
@item [:ascii:]
-This matches any @acronym{ASCII} (unibyte) character.
+This matches any @acronym{ASCII} character (codes 0--127).
@item [:alnum:]
This matches any letter or digit. (At present, for multibyte
characters, it matches anything that has word syntax.)
@item [:lower:]
This matches any lower-case letter, as determined by
the current case table (@pxref{Case Tables}).
+@item [:multibyte:]
+This matches any multibyte character (@pxref{Text Representations}).
@item [:nonascii:]
-This matches any non-@acronym{ASCII} (multibyte) character.
+This matches any non-@acronym{ASCII} character.
@item [:print:]
This matches printing characters---everything except @acronym{ASCII} control
characters and the delete character.
@item [:space:]
This matches any character that has whitespace syntax
(@pxref{Syntax Class Table}).
+@item [:unibyte:]
+This matches any unibyte character (@pxref{Text Representations}).
@item [:upper:]
This matches any upper-case letter, as determined by
the current case table (@pxref{Case Tables}).
@kindex invalid-regexp
Not every string is a valid regular expression. For example, a string
-with unbalanced square brackets is invalid (with a few exceptions, such
-as @samp{[]]}), and so is a string that ends with a single @samp{\}. If
+that ends inside a character alternative without terminating @samp{]}
+is invalid, and so is a string that ends with a single @samp{\}. If
an invalid regular expression is passed to any of the search functions,
an @code{invalid-regexp} error is signaled.
@var{regexp}, and leaves point at the end of the first match found.
It returns the new value of point.
-If @var{limit} is non-@code{nil} (it must be a position in the current
-buffer), then it is the upper bound to the search. No match extending
-after that position is accepted.
+If @var{limit} is non-@code{nil}, it must be a position in the current
+buffer. It specifies the upper bound to the search. No match
+extending after that position is accepted.
-If @var{repeat} is supplied (it must be a positive number), then the
-search is repeated that many times (each time starting at the end of the
-previous time's match). If all these successive searches succeed, the
-function succeeds, moving point and returning its new value. Otherwise
-the function fails.
+If @var{repeat} is supplied, it must be a positive number; the search
+is repeated that many times; each repetition starts at the end of the
+previous match. If all these successive searches succeed, the search
+succeeds, moving point and returning its new value. Otherwise the
+search fails. What @code{re-search-forward} does when the search
+fails depends on the value of @var{noerror}:
-What happens when the function fails depends on the value of
-@var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed}
-error is signaled. If @var{noerror} is @code{t},
-@code{re-search-forward} does nothing and returns @code{nil}. If
-@var{noerror} is neither @code{nil} nor @code{t}, then
-@code{re-search-forward} moves point to @var{limit} (or the end of the
-accessible portion of the buffer) and returns @code{nil}.
+@table @asis
+@item @code{nil}
+Signal a @code{search-failed} error.
+@item @code{t}
+Do nothing and return @code{nil}.
+@item anything else
+Move point to @var{limit} (or the end of the accessible portion of the
+buffer) and return @code{nil}.
+@end table
In the following example, point is initially before the @samp{T}.
Evaluating the search call moves point to the end of that line (between
@end example
@end defun
+@defvar search-spaces-regexp
+If this variable is non-@code{nil}, it should be a regular expression
+that says how to search for whitespace. In that case, any group of
+spaces in a regular expression being searched for stands for use of
+this regular expression. However, spaces inside of constructs such as
+@samp{[@dots{}]} and @samp{*}, @samp{+}, @samp{?} are not affected by
+@code{search-spaces-regexp}.
+
+Since this variable affects all regular expression search and match
+constructs, you should bind it temporarily for as small as possible
+a part of the code.
+@end defvar
+
@node POSIX Regexps
@section POSIX Regular Expression Searching
matching.
@end defun
-@ignore
-@deffn Command delete-matching-lines regexp
-This function is identical to @code{delete-non-matching-lines}, save
-that it deletes what @code{delete-non-matching-lines} keeps.
-
-In the example below, point is located on the first line of text.
-
-@example
-@group
----------- Buffer: foo ----------
-We hold these truths
-to be self-evident,
-that all men are created
-equal, and that they are
----------- Buffer: foo ----------
-@end group
-
-@group
-(delete-matching-lines "the")
- @result{} nil
-
----------- Buffer: foo ----------
-to be self-evident,
-that all men are created
----------- Buffer: foo ----------
-@end group
-@end example
-@end deffn
-
-@deffn Command flush-lines regexp
-This function is the same as @code{delete-matching-lines}.
-@end deffn
-
-@defun delete-non-matching-lines regexp
-This function deletes all lines following point which don't
-contain a match for the regular expression @var{regexp}.
-@end defun
-
-@deffn Command keep-lines regexp
-This function is the same as @code{delete-non-matching-lines}.
-@end deffn
-
-@deffn Command how-many regexp
-This function counts the number of matches for @var{regexp} there are in
-the current buffer following point. It prints this number in
-the echo area, returning the string printed.
-@end deffn
-
-@deffn Command count-matches regexp
-This function is a synonym of @code{how-many}.
-@end deffn
-
-@deffn Command list-matching-lines regexp &optional nlines
-This function is a synonym of @code{occur}.
-Show all lines following point containing a match for @var{regexp}.
-Display each line with @var{nlines} lines before and after,
-or @code{-}@var{nlines} before if @var{nlines} is negative.
-@var{nlines} defaults to @code{list-matching-lines-default-context-lines}.
-Interactively it is the prefix arg.
-
-The lines are shown in a buffer named @samp{*Occur*}.
-It serves as a menu to find any of the occurrences in this buffer.
-@kbd{C-h m} (@code{describe-mode}) in that buffer gives help.
-@end deffn
-
-@defopt list-matching-lines-default-context-lines
-Default value is 0.
-Default number of context lines to include around a @code{list-matching-lines}
-match. A negative number means to include that many lines before the match.
-A positive number means to include that many lines both before and after.
-@end defopt
-@end ignore
-
-@node Search and Replace
-@section Search and Replace
-@cindex replacement
-
-@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map start end
-This function is the guts of @code{query-replace} and related
-commands. It searches for occurrences of @var{from-string} in the
-text between positions @var{start} and @var{end} and replaces some or
-all of them. If @var{start} is @code{nil} (or omitted), point is used
-instead, and the end of the buffer's accessible portion is used for
-@var{end}.
-
-If @var{query-flag} is @code{nil}, it replaces all
-occurrences; otherwise, it asks the user what to do about each one.
-
-If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is
-considered a regular expression; otherwise, it must match literally. If
-@var{delimited-flag} is non-@code{nil}, then only replacements
-surrounded by word boundaries are considered.
-
-The argument @var{replacements} specifies what to replace occurrences
-with. If it is a string, that string is used. It can also be a list of
-strings, to be used in cyclic order.
-
-If @var{replacements} is a cons cell, @code{(@var{function}
-. @var{data})}, this means to call @var{function} after each match to
-get the replacement text. This function is called with two arguments:
-@var{data}, and the number of replacements already made.
-
-If @var{repeat-count} is non-@code{nil}, it should be an integer. Then
-it specifies how many times to use each of the strings in the
-@var{replacements} list before advancing cyclically to the next one.
-
-If @var{from-string} contains upper-case letters, then
-@code{perform-replace} binds @code{case-fold-search} to @code{nil}, and
-it uses the @code{replacements} without altering the case of them.
-
-Normally, the keymap @code{query-replace-map} defines the possible user
-responses for queries. The argument @var{map}, if non-@code{nil}, is a
-keymap to use instead of @code{query-replace-map}.
-
-@strong{Usage note:} Do not use this function in your own programs
-unless you want to do something very similar to what
-@code{query-replace} does, including setting the mark and possibly
-querying the user. For most purposes a simple loop like, for
-instance:
-
-@example
-(while (re-search-forward "foo[ \t]+bar" nil t)
- (replace-match "foobar"))
-@end example
-
-@noindent
-is preferable. It runs faster and avoids side effects, such as
-setting the mark. @xref{Replacing Match,, Replacing the Text that
-Matched}, for a description of @code{replace-match}.
-@end defun
-
-@defvar query-replace-map
-This variable holds a special keymap that defines the valid user
-responses for @code{query-replace} and related functions, as well as
-@code{y-or-n-p} and @code{map-y-or-n-p}. It is unusual in two ways:
-
-@itemize @bullet
-@item
-The ``key bindings'' are not commands, just symbols that are meaningful
-to the functions that use this map.
-
-@item
-Prefix keys are not supported; each key binding must be for a
-single-event key sequence. This is because the functions don't use
-@code{read-key-sequence} to get the input; instead, they read a single
-event and look it up ``by hand.''
-@end itemize
-@end defvar
-
-Here are the meaningful ``bindings'' for @code{query-replace-map}.
-Several of them are meaningful only for @code{query-replace} and
-friends.
-
-@table @code
-@item act
-Do take the action being considered---in other words, ``yes.''
-
-@item skip
-Do not take action for this question---in other words, ``no.''
-
-@item exit
-Answer this question ``no,'' and give up on the entire series of
-questions, assuming that the answers will be ``no.''
-
-@item act-and-exit
-Answer this question ``yes,'' and give up on the entire series of
-questions, assuming that subsequent answers will be ``no.''
-
-@item act-and-show
-Answer this question ``yes,'' but show the results---don't advance yet
-to the next question.
-
-@item automatic
-Answer this question and all subsequent questions in the series with
-``yes,'' without further user interaction.
-
-@item backup
-Move back to the previous place that a question was asked about.
-
-@item edit
-Enter a recursive edit to deal with this question---instead of any
-other action that would normally be taken.
-
-@item delete-and-edit
-Delete the text being considered, then enter a recursive edit to replace
-it.
-
-@item recenter
-Redisplay and center the window, then ask the same question again.
-
-@item quit
-Perform a quit right away. Only @code{y-or-n-p} and related functions
-use this answer.
-
-@item help
-Display some help, then ask again.
-@end table
-
@node Match Data
@section The Match Data
@cindex match data
Emacs keeps track of the start and end positions of the segments of
-text found during a search. This means, for example, that you can
-search for a complex pattern, such as a date in an Rmail message, and
-then extract parts of the match under control of the pattern.
+text found during a search; this is called the @dfn{match data}.
+Thanks to the match data, you can search for a complex pattern, such
+as a date in a mail message, and then extract parts of the match under
+control of the pattern.
Because the match data normally describe the most recent search only,
you must be careful not to do another search inadvertently between the
@node Replacing Match
@subsection Replacing the Text that Matched
- This function replaces the text matched by the last search with
-@var{replacement}.
+ This function replaces all or part of the text matched by the last
+search. It works by means of the match data.
@cindex case in replacements
@defun replace-match replacement &optional fixedcase literal string subexp
expressions can have subexpressions---after a simple string search, the
only information available is about the entire match.
+ Every successful search sets the match data. Therefore, you should
+query the match data immediately after searching, before calling any
+other function that might perform another search. Alternatively, you
+may save and restore the match data (@pxref{Saving Match Data}) around
+the call to functions that could perform another search.
+
A search which fails may or may not alter the match data. In the
past, a failing search did not do this, but we may change it in the
future. So don't try to rely on the value of the match data after
The functions @code{match-data} and @code{set-match-data} read or
write the entire match data, all at once.
-@defun match-data &optional integers reuse
-This function returns a newly constructed list containing all the
-information on what text the last search matched. Element zero is the
-position of the beginning of the match for the whole expression; element
-one is the position of the end of the match for the expression. The
-next two elements are the positions of the beginning and end of the
-match for the first subexpression, and so on. In general, element
+@defun match-data &optional integers reuse reseat
+This function returns a list of positions (markers or integers) that
+record all the information on what text the last search matched.
+Element zero is the position of the beginning of the match for the
+whole expression; element one is the position of the end of the match
+for the expression. The next two elements are the positions of the
+beginning and end of the match for the first subexpression, and so on.
+In general, element
@ifnottex
number 2@var{n}
@end ifnottex
@end tex
corresponds to @code{(match-end @var{n})}.
-All the elements are markers or @code{nil} if matching was done on a
-buffer and all are integers or @code{nil} if matching was done on a
-string with @code{string-match}. If @var{integers} is
-non-@code{nil}, then the elements are integers or @code{nil}, even if
-matching was done on a buffer. In that case, the buffer itself is
-appended as an additional element at the end of the list
-to facilitate complete restoration of the match data. Also,
-@code{match-beginning} and
-@code{match-end} always return integers or @code{nil}.
+Normally all the elements are markers or @code{nil}, but if
+@var{integers} is non-@code{nil}, that means to use integers instead
+of markers. (In that case, the buffer itself is appended as an
+additional element at the end of the list, to facilitate complete
+restoration of the match data.) If the last match was done on a
+string with @code{string-match}, then integers are always used,
+since markers can't point into a string.
If @var{reuse} is non-@code{nil}, it should be a list. In that case,
@code{match-data} stores the match data in @var{reuse}. That is,
have the right length. If it is not long enough to contain the match
data, it is extended. If it is too long, the length of @var{reuse}
stays the same, but the elements that were not used are set to
-@code{nil}. The purpose of this feature is to avoid producing too
-much garbage, that would later have to be collected.
+@code{nil}. The purpose of this feature is to reduce the need for
+garbage collection.
+
+If @var{reseat} is non-@code{nil}, all markers on the @var{reuse} list
+are reseated to point to nowhere.
As always, there must be no possibility of intervening searches between
the call to a search function and the call to @code{match-data} that is
@end example
@end defun
-@defun set-match-data match-list
+@defun set-match-data match-list &optional reseat
This function sets the match data from the elements of @var{match-list},
which should be a list that was the value of a previous call to
@code{match-data}. (More precisely, anything that has the same format
If @var{match-list} refers to a buffer that doesn't exist, you don't get
an error; that sets the match data in a meaningless but harmless way.
+If @var{reseat} is non-@code{nil}, all markers on the @var{match-list} list
+are reseated to point to nowhere.
+
@findex store-match-data
@code{store-match-data} is a semi-obsolete alias for @code{set-match-data}.
@end defun
@end smallexample
@end ignore
-@node Searching and Case
-@section Searching and Case
-@cindex searching and case
+@node Search and Replace
+@section Search and Replace
+@cindex replacement
- By default, searches in Emacs ignore the case of the text they are
-searching through; if you specify searching for @samp{FOO}, then
-@samp{Foo} or @samp{foo} is also considered a match. This applies to
-regular expressions, too; thus, @samp{[aB]} would match @samp{a} or
-@samp{A} or @samp{b} or @samp{B}.
+ If you want to find all matches for a regexp in part of the buffer,
+and replace them, the best way is to write an explicit loop using
+@code{re-search-forward} and @code{replace-match}, like this:
- If you do not want this feature, set the variable
-@code{case-fold-search} to @code{nil}. Then all letters must match
-exactly, including case. This is a buffer-local variable; altering the
-variable affects only the current buffer. (@xref{Intro to
-Buffer-Local}.) Alternatively, you may change the value of
-@code{default-case-fold-search}, which is the default value of
-@code{case-fold-search} for buffers that do not override it.
+@example
+(while (re-search-forward "foo[ \t]+bar" nil t)
+ (replace-match "foobar"))
+@end example
- Note that the user-level incremental search feature handles case
-distinctions differently. When given a lower case letter, it looks for
-a match of either case, but when given an upper case letter, it looks
-for an upper case letter only. But this has nothing to do with the
-searching functions used in Lisp code.
+@noindent
+@xref{Replacing Match,, Replacing the Text that Matched}, for a
+description of @code{replace-match}.
+
+ However, replacing matches in a string is more complex, especially
+if you want to do it efficiently. So Emacs provides a function to do
+this.
+
+@defun replace-regexp-in-string regexp rep string &optional fixedcase literal subexp start
+This function copies @var{string} and searches it for matches for
+@var{regexp}, and replaces them with @var{rep}. It returns the
+modified copy. If @var{start} is non-@code{nil}, the search for
+matches starts at that index in @var{string}, so matches starting
+before that index are not changed.
+
+This function uses @code{replace-match} to do the replacement, and it
+passes the optional arguments @var{fixedcase}, @var{literal} and
+@var{subexp} along to @code{replace-match}.
+
+Instead of a string, @var{rep} can be a function. In that case,
+@code{replace-regexp-in-string} calls @var{rep} for each match,
+passing the text of the match as its sole argument. It collects the
+value @var{rep} returns and passes that to @code{replace-match} as the
+replacement string. The match-data at this point are the result
+of matching @var{regexp} against a substring of @var{string}.
+@end defun
-@defopt case-replace
-This variable determines whether the higher level replacement
-functions should preserve case. If the variable is @code{nil}, that
-means to use the replacement text verbatim. A non-@code{nil} value
-means to convert the case of the replacement text according to the
-text being replaced.
+ If you want to write a command along the lines of @code{query-replace},
+you can use @code{perform-replace} to do the work.
-This variable is used by passing it as an argument to the function
-@code{replace-match}. @xref{Replacing Match}.
-@end defopt
+@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map start end
+This function is the guts of @code{query-replace} and related
+commands. It searches for occurrences of @var{from-string} in the
+text between positions @var{start} and @var{end} and replaces some or
+all of them. If @var{start} is @code{nil} (or omitted), point is used
+instead, and the end of the buffer's accessible portion is used for
+@var{end}.
-@defopt case-fold-search
-This buffer-local variable determines whether searches should ignore
-case. If the variable is @code{nil} they do not ignore case; otherwise
-they do ignore case.
-@end defopt
+If @var{query-flag} is @code{nil}, it replaces all
+occurrences; otherwise, it asks the user what to do about each one.
-@defvar default-case-fold-search
-The value of this variable is the default value for
-@code{case-fold-search} in buffers that do not override it. This is the
-same as @code{(default-value 'case-fold-search)}.
+If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is
+considered a regular expression; otherwise, it must match literally. If
+@var{delimited-flag} is non-@code{nil}, then only replacements
+surrounded by word boundaries are considered.
+
+The argument @var{replacements} specifies what to replace occurrences
+with. If it is a string, that string is used. It can also be a list of
+strings, to be used in cyclic order.
+
+If @var{replacements} is a cons cell, @code{(@var{function}
+. @var{data})}, this means to call @var{function} after each match to
+get the replacement text. This function is called with two arguments:
+@var{data}, and the number of replacements already made.
+
+If @var{repeat-count} is non-@code{nil}, it should be an integer. Then
+it specifies how many times to use each of the strings in the
+@var{replacements} list before advancing cyclically to the next one.
+
+If @var{from-string} contains upper-case letters, then
+@code{perform-replace} binds @code{case-fold-search} to @code{nil}, and
+it uses the @code{replacements} without altering the case of them.
+
+Normally, the keymap @code{query-replace-map} defines the possible
+user responses for queries. The argument @var{map}, if
+non-@code{nil}, specifies a keymap to use instead of
+@code{query-replace-map}.
+@end defun
+
+@defvar query-replace-map
+This variable holds a special keymap that defines the valid user
+responses for @code{perform-replace} and the commands that use it, as
+well as @code{y-or-n-p} and @code{map-y-or-n-p}. This map is unusual
+in two ways:
+
+@itemize @bullet
+@item
+The ``key bindings'' are not commands, just symbols that are meaningful
+to the functions that use this map.
+
+@item
+Prefix keys are not supported; each key binding must be for a
+single-event key sequence. This is because the functions don't use
+@code{read-key-sequence} to get the input; instead, they read a single
+event and look it up ``by hand.''
+@end itemize
@end defvar
+Here are the meaningful ``bindings'' for @code{query-replace-map}.
+Several of them are meaningful only for @code{query-replace} and
+friends.
+
+@table @code
+@item act
+Do take the action being considered---in other words, ``yes.''
+
+@item skip
+Do not take action for this question---in other words, ``no.''
+
+@item exit
+Answer this question ``no,'' and give up on the entire series of
+questions, assuming that the answers will be ``no.''
+
+@item act-and-exit
+Answer this question ``yes,'' and give up on the entire series of
+questions, assuming that subsequent answers will be ``no.''
+
+@item act-and-show
+Answer this question ``yes,'' but show the results---don't advance yet
+to the next question.
+
+@item automatic
+Answer this question and all subsequent questions in the series with
+``yes,'' without further user interaction.
+
+@item backup
+Move back to the previous place that a question was asked about.
+
+@item edit
+Enter a recursive edit to deal with this question---instead of any
+other action that would normally be taken.
+
+@item delete-and-edit
+Delete the text being considered, then enter a recursive edit to replace
+it.
+
+@item recenter
+Redisplay and center the window, then ask the same question again.
+
+@item quit
+Perform a quit right away. Only @code{y-or-n-p} and related functions
+use this answer.
+
+@item help
+Display some help, then ask again.
+@end table
+
@node Standard Regexps
@section Standard Regular Expressions Used in Editing
@cindex regexps used standardly in editing