@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/searching
-@node Searching and Matching, Syntax Tables, Text, Top
+@node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top
@chapter Searching and Matching
@cindex searching
These are the primitive functions for searching through the text in a
buffer. They are meant for use in programs, but you may call them
-interactively. If you do so, they prompt for the search string;
-@var{limit} and @var{noerror} are set to @code{nil}, and @var{repeat}
-is set to 1.
+interactively. If you do so, they prompt for the search string; the
+arguments @var{limit} and @var{noerror} are @code{nil}, and @var{repeat}
+is 1.
+
+ These search functions convert the search string to multibyte if the
+buffer is multibyte; they convert the search string to unibyte if the
+buffer is unibyte. @xref{Text Representations}.
@deffn Command search-forward string &optional limit noerror repeat
- This function searches forward from point for an exact match for
+This function searches forward from point for an exact match for
@var{string}. If successful, it sets point to the end of the occurrence
found, and returns the new value of point. If no match is found, the
value and side effects depend on @var{noerror} (see below).
@c Emacs 19 feature
- In the following example, point is initially at the beginning of the
+In the following example, point is initially at the beginning of the
line. Then @code{(search-forward "fox")} moves point after the last
letter of @samp{fox}:
@end group
@end example
- The argument @var{limit} specifies the upper bound to the search. (It
+The argument @var{limit} specifies the upper bound to the search. (It
must be a position in the current buffer.) No match extending after
that position is accepted. If @var{limit} is omitted or @code{nil}, it
defaults to the end of the accessible portion of the buffer.
@kindex search-failed
- What happens when the search fails depends on the value of
+What happens when the search 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{search-forward}
returns @code{nil} and does nothing. If @var{noerror} is neither
@code{nil} nor @code{t}, then @code{search-forward} moves point to the
-upper bound and returns @code{nil}. (It would be more consistent now
-to return the new position of point in that case, but some programs
-may depend on a value of @code{nil}.)
+upper bound and returns @code{nil}. (It would be more consistent now to
+return the new position of point in that case, but some existing
+programs may depend on a value of @code{nil}.)
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
@menu
* Syntax of Regexps:: Rules for writing regular expressions.
+* Regexp Functions:: Functions for operating on regular expressions.
* Regexp Example:: Illustrates regular expression syntax.
@end menu
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
+ 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
@samp{f} and no other string. (It does @emph{not} match the string
-@samp{ff}.) Likewise, @samp{o} is a regular expression that matches
-only @samp{o}.@refill
+@samp{fg}, but it does match a @emph{part} of that string.) Likewise,
+@samp{o} is a regular expression that matches only @samp{o}.@refill
-Any two regular expressions @var{a} and @var{b} can be concatenated. The
+ Any two regular expressions @var{a} and @var{b} can be concatenated. The
result is a regular expression that matches a string if @var{a} matches
some amount of the beginning of that string and @var{b} matches the rest of
the string.@refill
-As a simple example, we can concatenate the regular expressions @samp{f}
+ As a simple example, we can concatenate the regular expressions @samp{f}
and @samp{o} to get the regular expression @samp{fo}, which matches only
the string @samp{fo}. Still trivial. To do something more powerful, you
-need to use one of the special characters. Here is a list of them:
+need to use one of the special regular expression constructs.
+
+@menu
+* Regexp Special:: Special characters in regular expressions.
+* Char Classes:: Character classes used in regular expressions.
+* Regexp Backslash:: Backslash-sequences in regular expressions.
+@end menu
+
+@node Regexp Special
+@subsubsection Special Characters in Regular Expressions
+
+ Here is a list of the characters that are special in a regular
+expression.
-@need 1200
-@table @kbd
-@item .@: @r{(Period)}
+@need 800
+@table @asis
+@item @samp{.}@: @r{(Period)}
@cindex @samp{.} in regexp
is a special character that matches any single character except a newline.
Using concatenation, we can make regular expressions like @samp{a.b}, which
matches any three-character string that begins with @samp{a} and ends with
@samp{b}.@refill
-@item *
+@item @samp{*}
@cindex @samp{*} in regexp
is not a construct by itself; it is a postfix operator that means to
match the preceding regular expression repetitively as many times as
expression. Thus, @samp{fo*} has a repeating @samp{o}, not a repeating
@samp{fo}. It matches @samp{f}, @samp{fo}, @samp{foo}, and so on.
-The matcher processes a @samp{*} 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 @samp{*}-modified construct in case that makes
-it possible to match the rest of the pattern. For example, in matching
-@samp{ca*ar} against the string @samp{caaar}, the @samp{a*} first
-tries to match all three @samp{a}s; but the rest of the pattern is
+The matcher processes a @samp{*} 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 @samp{*}-modified construct in the hope that that will
+make it possible to match the rest of the pattern. For example, in
+matching @samp{ca*ar} against the string @samp{caaar}, the @samp{a*}
+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
+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 if they specify
backtracking loops. For example, it could take hours for the regular
-expression @samp{\(x+y*\)*a} to match the sequence
-@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}. The slowness is because
-Emacs must try each imaginable way of grouping the 35 @samp{x}'s before
-concluding that none of them can work. To make sure your regular
-expressions run fast, check nested repetitions carefully.
-
-@item +
+expression @samp{\(x+y*\)*a} to try to match the sequence
+@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}, before it ultimately fails.
+The slowness is because Emacs must try each imaginable way of grouping
+the 35 @samp{x}s before concluding that none of them can work. To make
+sure your regular expressions run fast, check nested repetitions
+carefully.
+
+@item @samp{+}
@cindex @samp{+} in regexp
is a postfix operator, similar to @samp{*} except that it must match
the preceding expression at least once. So, for example, @samp{ca+r}
matches the strings @samp{car} and @samp{caaaar} but not the string
@samp{cr}, whereas @samp{ca*r} matches all three strings.
-@item ?
+@item @samp{?}
@cindex @samp{?} in regexp
-is a postfix operator, similar to @samp{*} except that it can match the
+is a postfix operator, similar to @samp{*} except that it must match the
preceding expression either once or not at all. For example,
@samp{ca?r} matches @samp{car} or @samp{cr}; nothing else.
-@item [ @dots{} ]
-@cindex character set (in regexp)
+@item @samp{*?}, @samp{+?}, @samp{??}
+These are ``non-greedy'' variants of the operators @samp{*}, @samp{+}
+and @samp{?}. Where those operators match the largest possible
+substring (consistent with matching the entire containing expression),
+the non-greedy variants match the smallest possible substring
+(consistent with matching the entire containing expression).
+
+For example, the regular expression @samp{c[ad]*a} when applied to the
+string @samp{cdaaada} matches the whole string; but the regular
+expression @samp{c[ad]*?a}, applied to that same string, matches just
+@samp{cda}. (The smallest possible match here for @samp{[ad]*?} that
+permits the whole expression to match is @samp{d}.)
+
+@item @samp{[ @dots{} ]}
+@cindex character alternative (in regexp)
@cindex @samp{[} in regexp
@cindex @samp{]} in regexp
-is a @dfn{character set}, which begins with @samp{[} and is terminated
-by @samp{]}. In the simplest case, the characters between the two
-brackets are what this set can match.
+is a @dfn{character alternative}, which begins with @samp{[} and is
+terminated by @samp{]}. In the simplest case, the characters between
+the two brackets are what this character alternative can match.
Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and
@samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s
(including the empty string), from which it follows that @samp{c[ad]*r}
matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc.
-You can also include character ranges in a character set, by writing the
-starting and ending characters with a @samp{-} between them. Thus,
-@samp{[a-z]} matches any lower-case ASCII letter. Ranges may be
+You can also include character ranges in a character alternative, by
+writing the starting and ending characters with a @samp{-} between them.
+Thus, @samp{[a-z]} matches any lower-case @sc{ascii} letter. Ranges may be
intermixed freely with individual characters, as in @samp{[a-z$%.]},
-which matches any lower case ASCII letter or @samp{$}, @samp{%} or
+which matches any lower case @sc{ascii} letter or @samp{$}, @samp{%} or
period.
Note that the usual regexp special characters are not special inside a
-character set. A completely different set of special characters exists
-inside character sets: @samp{]}, @samp{-} and @samp{^}.
-
-To include a @samp{]} in a character set, you must make it the first
-character. For example, @samp{[]a]} matches @samp{]} or @samp{a}. To
-include a @samp{-}, write @samp{-} as the first or last character of the
-set, or put it after a range. Thus, @samp{[]-]} matches both @samp{]}
-and @samp{-}.
-
-To include @samp{^} in a set, put it anywhere but at the beginning of
-the set.
-
-@item [^ @dots{} ]
+character alternative. A completely different set of characters is
+special inside character alternatives: @samp{]}, @samp{-} and @samp{^}.
+
+To include a @samp{]} in a character alternative, you must make it the
+first character. For example, @samp{[]a]} matches @samp{]} or @samp{a}.
+To include a @samp{-}, write @samp{-} as the first or last character of
+the character alternative, or put it after a range. Thus, @samp{[]-]}
+matches both @samp{]} and @samp{-}.
+
+To include @samp{^} in a character alternative, put it anywhere but at
+the beginning.
+
+The beginning and end of a range of multibyte characters must be in
+the same character set (@pxref{Character Sets}). Thus,
+@code{"[\x8e0-\x97c]"} is invalid because character 0x8e0 (@samp{a}
+with grave accent) is in the Emacs character set for Latin-1 but the
+character 0x97c (@samp{u} with diaeresis) is in the Emacs character
+set for Latin-2. (We use Lisp string syntax to write that example,
+and a few others in the next few paragraphs, in order to include hex
+escape sequences in them.)
+
+If a range starts with a unibyte character @var{c} and ends with a
+multibyte character @var{c2}, the range is divided into two parts: one
+is @samp{@var{c}..?\377}, the other is @samp{@var{c1}..@var{c2}}, where
+@var{c1} is the first character of the charset to which @var{c2}
+belongs.
+
+You cannot always match all non-@sc{ascii} characters with the regular
+expression @code{"[\200-\377]"}. This works when searching a unibyte
+buffer or string (@pxref{Text Representations}), but not in a multibyte
+buffer or string, because many non-@sc{ascii} characters have codes
+above octal 0377. However, the regular expression @code{"[^\000-\177]"}
+does match all non-@sc{ascii} characters (see below regarding @samp{^}),
+in both multibyte and unibyte representations, because only the
+@sc{ascii} characters are excluded.
+
+Starting in Emacs 21, 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
+not feasible in practice, since some classes include thousands of
+different characters.
+
+@item @samp{[^ @dots{} ]}
@cindex @samp{^} in regexp
-@samp{[^} begins a @dfn{complemented character set}, which matches any
+@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{^} is not special in a character set unless it is the first
+@samp{^} is not special in a character alternative unless it is the first
character. The character following the @samp{^} is treated as if it
were first (in other words, @samp{-} and @samp{]} are not special there).
-A complemented character set can match a newline, unless newline is
+A complemented character alternative 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 @code{grep}.
-@item ^
-@cindex @samp{^} in regexp
+@item @samp{^}
@cindex beginning of line in regexp
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
the beginning of a line.
When matching a string instead of a buffer, @samp{^} matches at the
-beginning of the string or after a newline character @samp{\n}.
+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{\(} or @samp{\|}.
-@item $
+@item @samp{$}
@cindex @samp{$} in regexp
+@cindex end of line in regexp
is similar to @samp{^} but matches only at the end of a line. Thus,
@samp{x+$} matches a string of one @samp{x} or more at the end of a line.
When matching a string instead of a buffer, @samp{$} matches at the end
-of the string or before a newline character @samp{\n}.
+of the string or before a newline character.
-@item \
+For historical compatibility reasons, @samp{$} can be used only at the
+end of the regular expression, or before @samp{\)} or @samp{\|}.
+
+@item @samp{\}
@cindex @samp{\} in regexp
has two functions: it quotes the special characters (including
@samp{\}), and it introduces additional special constructs.
can act. It is poor practice to depend on this behavior; quote the
special character anyway, regardless of where it appears.@refill
-For the most part, @samp{\} followed by any character matches only
-that character. However, there are several exceptions: two-character
-sequences starting with @samp{\} which have special meanings. The
-second character in the sequence is always an ordinary character on
-their own. Here is a table of @samp{\} constructs.
+@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:
+
+@table @samp
+@item [:ascii:]
+This matches any @sc{ascii} (unibyte) character.
+@item [:alnum:]
+This matches any letter or digit. (At present, for multibyte
+characters, it matches anything that has word syntax.)
+@item [:alpha:]
+This matches any letter. (At present, for multibyte characters, it
+matches anything that has word syntax.)
+@item [:blank:]
+This matches space and tab only.
+@item [:cntrl:]
+This matches any @sc{ascii} control character.
+@item [:digit:]
+This matches @samp{0} through @samp{9}. Thus, @samp{[-+[:digit:]]}
+matches any digit, as well as @samp{+} and @samp{-}.
+@item [:graph:]
+This matches graphic characters---everything except @sc{ascii} control
+characters, space, and the delete character.
+@item [:lower:]
+This matches any lower-case letter, as determined by
+the current case table (@pxref{Case Tables}).
+@item [:nonascii:]
+This matches any non-@sc{ascii} (multibyte) character.
+@item [:print:]
+This matches printing characters---everything except @sc{ascii} control
+characters and the delete character.
+@item [:punct:]
+This matches any punctuation character. (At present, for multibyte
+characters, it matches anything that has non-word syntax.)
+@item [:space:]
+This matches any character that has whitespace syntax
+(@pxref{Syntax Class Table}).
+@item [:upper:]
+This matches any upper-case letter, as determined by
+the current case table (@pxref{Case Tables}).
+@item [:word:]
+This matches any character that has word syntax (@pxref{Syntax Class
+Table}).
+@item [:xdigit:]
+This matches the hexadecimal digits: @samp{0} through @samp{9}, @samp{a}
+through @samp{f} and @samp{A} through @samp{F}.
+@end table
+
+@node Regexp Backslash
+@subsubsection Backslash Constructs in Regular Expressions
+
+ For the most part, @samp{\} followed by any character matches only
+that character. However, there are several exceptions: certain
+two-character sequences starting with @samp{\} that have special
+meanings. (The character after the @samp{\} in such a sequence is
+always ordinary when used on its own.) Here is a table of the special
+@samp{\} constructs.
-@table @kbd
+@table @samp
@item \|
@cindex @samp{|} in regexp
@cindex regexp alternative
surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of
@samp{\|}.@refill
-Full backtracking capability exists to handle multiple uses of @samp{\|}.
+Full backtracking capability exists to handle multiple uses of
+@samp{\|}, if you use the POSIX regular expression functions
+(@pxref{POSIX Regexps}).
+
+@item \@{@var{m}\@}
+is a postfix operator that repeats the previous pattern exactly @var{m}
+times. Thus, @samp{x\@{5\@}} matches the string @samp{xxxxx}
+and nothing else. @samp{c[ad]\@{3\@}r} matches string such as
+@samp{caaar}, @samp{cdddr}, @samp{cadar}, and so on.
+
+@item \@{@var{m},@var{n}\@}
+is more general postfix operator that specifies repetition with a
+minimum of @var{m} repeats and a maximum of @var{n} repeats. If @var{m}
+is omitted, the minimum is 0; if @var{n} is omitted, there is no
+maximum.
+
+For example, @samp{c[ad]\@{1,2\@}r} matches the strings @samp{car},
+@samp{cdr}, @samp{caar}, @samp{cadr}, @samp{cdar}, and @samp{cddr}, and
+nothing else.@*
+@samp{\@{0,1\@}} or @samp{\@{,1\@}} is equivalent to @samp{?}. @*
+@samp{\@{0,\@}} or @samp{\@{,\@}} is equivalent to @samp{*}. @*
+@samp{\@{1,\@}} is equivalent to @samp{+}.
@item \( @dots{} \)
@cindex @samp{(} in regexp
@item
To enclose a complicated expression for the postfix operators @samp{*},
@samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches
-@samp{bananana}, etc., with any (zero or more) number of @samp{na}
-strings.@refill
+@samp{ba}, @samp{bana}, @samp{banana}, @samp{bananana}, etc., with any
+number (zero or more) of @samp{na} strings.
@item
-To record a matched substring for future reference.
+To record a matched substring for future reference with
+@samp{\@var{digit}} (see below).
@end enumerate
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 @samp{\( @dots{} \)} construct
-because there is no conflict in practice between the two meanings.
-Here is an explanation of this feature:
+parenthetical grouping; it is a separate feature that was assigned as a
+second meaning to the same @samp{\( @dots{} \)} construct because, in
+pratice, there was usually no conflict between the two meanings. But
+occasionally there is a conflict, and that led to the introduction of
+shy groups.
+
+@item \(?: @dots{} \)
+is the @dfn{shy group} construct. A shy group serves the first two
+purposes of an ordinary group (controlling the nesting of other
+operators), but it does not get a number, so you cannot refer back to
+its value with @samp{\@var{digit}}.
+
+Shy groups are particulary useful for mechanically-constructed regular
+expressions because they can be added automatically without altering the
+numbering of any ordinary, non-shy groups.
@item \@var{digit}
matches the same text that matched the @var{digit}th occurrence of a
matches any character whose syntax is @var{code}. Here @var{code} is a
character that represents a syntax code: thus, @samp{w} for word
constituent, @samp{-} for whitespace, @samp{(} for open parenthesis,
-etc. Represent a character of whitespace (which can be a newline) by
-either @samp{-} or a space character. @xref{Syntax Tables}, for a list
-of syntax codes and the characters that stand for them.
+etc. To represent whitespace syntax, use either @samp{-} or a space
+character. @xref{Syntax Class Table}, for a list of syntax codes and
+the characters that stand for them.
@item \S@var{code}
@cindex @samp{\S} in regexp
matches any character whose syntax is not @var{code}.
+
+@item \c@var{c}
+matches any character whose category is @var{c}. Here @var{c} is a
+character that represents a category: thus, @samp{c} for Chinese
+characters or @samp{g} for Greek characters in the standard category
+table.
+
+@item \C@var{c}
+matches any character whose category is not @var{c}.
@end table
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.
-@table @kbd
+@table @samp
@item \`
@cindex @samp{\`} in regexp
matches the empty string, but only at the beginning
an invalid regular expression is passed to any of the search functions,
an @code{invalid-regexp} error is signaled.
-@defun regexp-quote string
-This function returns a regular expression string that matches exactly
-@var{string} and nothing else. This allows you to request an exact
-string match when calling a function that wants a regular expression.
-
-@example
-@group
-(regexp-quote "^The cat$")
- @result{} "\\^The cat\\$"
-@end group
-@end example
-
-One use of @code{regexp-quote} is to combine an exact string match with
-context described as a regular expression. For example, this searches
-for the string that is the value of @code{string}, surrounded by
-whitespace:
-
-@example
-@group
-(re-search-forward
- (concat "\\s-" (regexp-quote string) "\\s-"))
-@end group
-@end example
-@end defun
-
@node Regexp Example
@comment node-name, next, previous, up
@subsection Complex Regexp Example
"[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*"
@end example
- In contrast, if you evaluate the variable @code{sentence-end}, you
+@noindent
+In contrast, if you evaluate the variable @code{sentence-end}, you
will see the following:
@example
@group
sentence-end
-@result{}
-"[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[
+ @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[
]*"
@end group
@end example
@table @code
@item [.?!]
-The first part of the pattern is a character set that matches any one of
-three characters: period, question mark, and exclamation mark. The
-match must begin with one of these three characters.
+The first part of the pattern is a character alternative that matches
+any one of three characters: period, question mark, and exclamation
+mark. The match must begin with one of these three characters.
@item []\"')@}]*
The second part of the pattern matches any closing braces and quotation
marks, zero or more of them, that may follow the period, question mark
or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in
a string. The @samp{*} at the end indicates that the immediately
-preceding regular expression (a character set, in this case) may be
+preceding regular expression (a character alternative, in this case) may be
repeated zero or more times.
@item \\($\\|@ $\\|\t\\|@ @ \\)
The third part of the pattern matches the whitespace that follows the
-end of a sentence: the end of a line, or a tab, or two spaces. The
-double backslashes mark the parentheses and vertical bars as regular
-expression syntax; the parentheses delimit a group and the vertical bars
-separate alternatives. The dollar sign is used to match the end of a
-line.
+end of a sentence: the end of a line (optionally with a space), or a
+tab, or two spaces. The double backslashes mark the parentheses and
+vertical bars as regular expression syntax; the parentheses delimit a
+group and the vertical bars separate alternatives. The dollar sign is
+used to match the end of a line.
@item [ \t\n]*
Finally, the last part of the pattern matches any additional whitespace
beyond the minimum needed to end a sentence.
@end table
+@node Regexp Functions
+@subsection Regular Expression Functions
+
+ These functions operate on regular expressions.
+
+@defun regexp-quote string
+This function returns a regular expression whose only exact match is
+@var{string}. Using this regular expression in @code{looking-at} will
+succeed only if the next characters in the buffer are @var{string};
+using it in a search function will succeed if the text being searched
+contains @var{string}.
+
+This allows you to request an exact string match or search when calling
+a function that wants a regular expression.
+
+@example
+@group
+(regexp-quote "^The cat$")
+ @result{} "\\^The cat\\$"
+@end group
+@end example
+
+One use of @code{regexp-quote} is to combine an exact string match with
+context described as a regular expression. For example, this searches
+for the string that is the value of @var{string}, surrounded by
+whitespace:
+
+@example
+@group
+(re-search-forward
+ (concat "\\s-" (regexp-quote string) "\\s-"))
+@end group
+@end example
+@end defun
+
+@defun regexp-opt strings &optional paren
+This function returns an efficient regular expression that will match
+any of the strings @var{strings}. This is useful when you need to make
+matching or searching as fast as possible---for example, for Font Lock
+mode.
+
+If the optional argument @var{paren} is non-@code{nil}, then the
+returned regular expression is always enclosed by at least one
+parentheses-grouping construct.
+
+This simplified definition of @code{regexp-opt} produces a
+regular expression which is equivalent to the actual value
+(but not as efficient):
+
+@example
+(defun regexp-opt (strings paren)
+ (let ((open-paren (if paren "\\(" ""))
+ (close-paren (if paren "\\)" "")))
+ (concat open-paren
+ (mapconcat 'regexp-quote strings "\\|")
+ close-paren)))
+@end example
+@end defun
+
+@defun regexp-opt-depth regexp
+This function returns the total number of grouping constructs
+(parenthesized expressions) in @var{regexp}.
+@end defun
+
@node Regexp Search
@section Regular Expression Searching
@cindex regular expression searching
@cindex regexp searching
@cindex searching for regexp
- In GNU Emacs, you can search for the next match for a regexp either
-incrementally or not. For incremental search commands, see @ref{Regexp
-Search, , Regular Expression Search, emacs, The GNU Emacs Manual}. Here
-we describe only the search functions useful in programs. The principal
-one is @code{re-search-forward}.
+ In GNU Emacs, you can search for the next match for a regular
+expression either incrementally or not. For incremental search
+commands, see @ref{Regexp Search, , Regular Expression Search, emacs,
+The GNU Emacs Manual}. Here we describe only the search functions
+useful in programs. The principal one is @code{re-search-forward}.
+
+ These search functions convert the regular expression to multibyte if
+the buffer is multibyte; they convert the regular expression to unibyte
+if the buffer is unibyte. @xref{Text Representations}.
@deffn Command re-search-forward regexp &optional limit noerror repeat
This function searches forward in the current buffer for a string of
buffer), then it is the upper bound to the search. No match extending
after that position is accepted.
-What happens when the search fails depends on the value of
+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.
+
+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
@code{re-search-forward} moves point to @var{limit} (or the end of the
buffer) and returns @code{nil}.
-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
-function succeeds, moving point and returning its new value. Otherwise
-the search fails.
-
In the following example, point is initially before the @samp{T}.
Evaluating the search call moves point to the end of that line (between
the @samp{t} of @samp{hat} and the newline).
beginning is as close as possible to the starting point. If
@code{re-search-backward} were a perfect mirror image, it would find the
match whose end is as close as possible. However, in fact it finds the
-match whose beginning is as close as possible. The reason is that
+match whose beginning is as close as possible. The reason for this is that
matching a regular expression at a given spot always works from
beginning to end, and starts at a specified beginning position.
A true mirror-image of @code{re-search-forward} would require a special
-feature for matching regexps from end to beginning. It's not worth the
-trouble of implementing that.
+feature for matching regular expressions from end to beginning. It's
+not worth the trouble of implementing that.
@end deffn
@defun string-match regexp string &optional start
match, as required by POSIX. This is much slower, so use these
functions only when you really need the longest match.
- In Emacs versions prior to 19.29, these functions did not exist, and
-the functions described above implemented full POSIX backtracking.
-
@defun posix-search-forward regexp &optional limit noerror repeat
This is like @code{re-search-forward} except that it performs the full
backtracking specified by the POSIX standard for regular expression
This function is a synonym of @code{how-many}.
@end deffn
-@deffn Command list-matching-lines regexp nlines
+@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,
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.
+@kbd{C-h m} (@code{describe-mode}) in that buffer gives help.
@end deffn
@defopt list-matching-lines-default-context-lines
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 cyclicly 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}.
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 read key sequence to
-get the input; instead, they read a single event and look it up ``by hand.''
+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
@section The Match Data
@cindex match data
- Emacs keeps track of the positions of the start and end of segments of
+ Emacs keeps track of the start and end positions of the segments of
text found during a regular expression 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
match data around it, to prevent it from being overwritten.
@menu
+* Replacing Match:: Replacing a substring that was matched.
* Simple Match Data:: Accessing single items of match data,
such as where a particular subexpression started.
-* Replacing Match:: Replacing a substring that was matched.
* Entire Match Data:: Accessing the entire match data at once, as a list.
* Saving Match Data:: Saving and restoring the match data.
@end menu
+@node Replacing Match
+@subsection Replacing the Text that Matched
+
+ This function replaces the text matched by the last search with
+@var{replacement}.
+
+@cindex case in replacements
+@defun replace-match replacement &optional fixedcase literal string subexp
+This function replaces the text in the buffer (or in @var{string}) that
+was matched by the last search. It replaces that text with
+@var{replacement}.
+
+If you did the last search in a buffer, you should specify @code{nil}
+for @var{string}. Then @code{replace-match} does the replacement by
+editing the buffer; it leaves point at the end of the replacement text,
+and returns @code{t}.
+
+If you did the search in a string, pass the same string as @var{string}.
+Then @code{replace-match} does the replacement by constructing and
+returning a new string.
+
+If @var{fixedcase} is non-@code{nil}, then the case of the replacement
+text is not changed; otherwise, the replacement text is converted to a
+different case depending upon the capitalization of the text to be
+replaced. If the original text is all upper case, the replacement text
+is converted to upper case. If the first word of the original text is
+capitalized, then the first word of the replacement text is capitalized.
+If the original text contains just one word, and that word is a capital
+letter, @code{replace-match} considers this a capitalized first word
+rather than all upper case.
+
+If @var{literal} is non-@code{nil}, then @var{replacement} is inserted
+exactly as it is, the only alterations being case changes as needed.
+If it is @code{nil} (the default), then the character @samp{\} is treated
+specially. If a @samp{\} appears in @var{replacement}, then it must be
+part of one of the following sequences:
+
+@table @asis
+@item @samp{\&}
+@cindex @samp{&} in replacement
+@samp{\&} stands for the entire text being replaced.
+
+@item @samp{\@var{n}}
+@cindex @samp{\@var{n}} in replacement
+@samp{\@var{n}}, where @var{n} is a digit, stands for the text that
+matched the @var{n}th subexpression in the original regexp.
+Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}.
+
+@item @samp{\\}
+@cindex @samp{\} in replacement
+@samp{\\} stands for a single @samp{\} in the replacement text.
+@end table
+
+If @var{subexp} is non-@code{nil}, that says to replace just
+subexpression number @var{subexp} of the regexp that was matched, not
+the entire match. For example, after matching @samp{foo \(ba*r\)},
+calling @code{replace-match} with 1 as @var{subexp} means to replace
+just the text that matched @samp{\(ba*r\)}.
+@end defun
+
@node Simple Match Data
@subsection Simple Match Data Access
expressions can have subexpressions---after a simple string search, the
only information available is about the entire match.
+ 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.
+
@defun match-string count &optional in-string
This function returns, as a string, the text matched in the last search
or match operation. It returns the entire text if @var{count} is zero,
If the last such operation was done against a string with
@code{string-match}, then you should pass the same string as the
-argument @var{in-string}. Otherwise, after a buffer search or match,
+argument @var{in-string}. After a buffer search or match,
you should omit @var{in-string} or pass @code{nil} for it; but you
should make sure that the current buffer when you call
@code{match-string} is the one in which you did the searching or
matching.
@end defun
+@defun match-string-no-properties count &optional in-string
+This function is like @code{match-string} except that the result
+has no text properties.
+@end defun
+
@defun match-beginning count
This function returns the position of the start of text matched by the
last regular expression searched for, or a subexpression of it.
If @var{count} is zero, then the value is the position of the start of
the entire match. Otherwise, @var{count} specifies a subexpression in
-the regular expresion, and the value of the function is the starting
+the regular expression, and the value of the function is the starting
position of the match for that subexpression.
The value is @code{nil} for a subexpression inside a @samp{\|}
(In this case, the index returned is a buffer position; the first
character of the buffer counts as 1.)
-@node Replacing Match
-@subsection Replacing the Text That Matched
-
- This function replaces the text matched by the last search with
-@var{replacement}.
-
-@cindex case in replacements
-@defun replace-match replacement &optional fixedcase literal string subexp
-This function replaces the text in the buffer (or in @var{string}) that
-was matched by the last search. It replaces that text with
-@var{replacement}.
-
-If you did the last search in a buffer, you should specify @code{nil}
-for @var{string}. Then @code{replace-match} does the replacement by
-editing the buffer; it leaves point at the end of the replacement text,
-and returns @code{t}.
-
-If you did the search in a string, pass the same string as @var{string}.
-Then @code{replace-match} does the replacement by constructing and
-returning a new string.
-
-If @var{fixedcase} is non-@code{nil}, then the case of the replacement
-text is not changed; otherwise, the replacement text is converted to a
-different case depending upon the capitalization of the text to be
-replaced. If the original text is all upper case, the replacement text
-is converted to upper case. If the first word of the original text is
-capitalized, then the first word of the replacement text is capitalized.
-If the original text contains just one word, and that word is a capital
-letter, @code{replace-match} considers this a capitalized first word
-rather than all upper case.
-
-If @code{case-replace} is @code{nil}, then case conversion is not done,
-regardless of the value of @var{fixed-case}. @xref{Searching and Case}.
-
-If @var{literal} is non-@code{nil}, then @var{replacement} is inserted
-exactly as it is, the only alterations being case changes as needed.
-If it is @code{nil} (the default), then the character @samp{\} is treated
-specially. If a @samp{\} appears in @var{replacement}, then it must be
-part of one of the following sequences:
-
-@table @asis
-@item @samp{\&}
-@cindex @samp{&} in replacement
-@samp{\&} stands for the entire text being replaced.
-
-@item @samp{\@var{n}}
-@cindex @samp{\@var{n}} in replacement
-@samp{\@var{n}}, where @var{n} is a digit, stands for the text that
-matched the @var{n}th subexpression in the original regexp.
-Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}.
-
-@item @samp{\\}
-@cindex @samp{\} in replacement
-@samp{\\} stands for a single @samp{\} in the replacement text.
-@end table
-
-If @var{subexp} is non-@code{nil}, that says to replace just
-subexpression number @var{subexp} of the regexp that was matched, not
-the entire match. For example, after matching @samp{foo \(ba*r\)},
-calling @code{replace-match} with 1 as @var{subexp} means to replace
-just the text that matched @samp{\(ba*r\)}.
-@end defun
-
@node Entire Match Data
@subsection Accessing the Entire Match Data
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
-@ifinfo
+@ifnottex
number 2@var{n}
-@end ifinfo
+@end ifnottex
@tex
number {\mathsurround=0pt $2n$}
@end tex
corresponds to @code{(match-beginning @var{n})}; and
element
-@ifinfo
+@ifnottex
number 2@var{n} + 1
-@end ifinfo
+@end ifnottex
@tex
number {\mathsurround=0pt $2n+1$}
@end tex
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}. (In Emacs 18 and earlier versions,
-markers were used even for matching on a string, except in the case
-of the integer 0.)
+string with @code{string-match}.
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
an error; that sets the match data in a meaningless but harmless way.
@findex store-match-data
-@code{store-match-data} is an alias for @code{set-match-data}.
+@code{store-match-data} is a semi-obsolete alias for @code{set-match-data}.
@end defun
@node Saving Match Data
You can save and restore the match data with @code{save-match-data}:
@defmac save-match-data body@dots{}
-This special form executes @var{body}, saving and restoring the match
+This macro executes @var{body}, saving and restoring the match
data around it.
@end defmac
- You can use @code{set-match-data} together with @code{match-data} to
-imitate the effect of the special form @code{save-match-data}. This is
-useful for writing code that can run in Emacs 18. Here is how:
+ You could use @code{set-match-data} together with @code{match-data} to
+imitate the effect of the special form @code{save-match-data}. Here is
+how:
@example
@group
(let ((data (match-data)))
(unwind-protect
- @dots{} ; @r{May change the original match data.}
+ @dots{} ; @r{Ok to change the original match data.}
(set-match-data data)))
@end group
@end example
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. Regexps, and in
-particular character sets, are included: thus, @samp{[aB]} would match
-@samp{a} or @samp{A} or @samp{b} or @samp{B}.
+@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
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 Lisp functions use.
+searching functions used in Lisp code.
@defopt case-replace
This variable determines whether the replacement functions should
replacement text verbatim. A non-@code{nil} value means to convert the
case of the replacement text according to the text being replaced.
-The function @code{replace-match} is where this variable actually has
-its effect. @xref{Replacing Match}.
+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
used for certain purposes in editing:
@defvar page-delimiter
-This is the regexp describing line-beginnings that separate pages. The
-default value is @code{"^\014"} (i.e., @code{"^^L"} or @code{"^\C-l"});
-this matches a line that starts with a formfeed character.
+This is the regular expression describing line-beginnings that separate
+pages. The default value is @code{"^\014"} (i.e., @code{"^^L"} or
+@code{"^\C-l"}); this matches a line that starts with a formfeed
+character.
@end defvar
The following two regular expressions should @emph{not} assume the
HCoop / bpt / emacs.git / blobdiff