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diff --git a/lispref/searching.texi b/lispref/searching.texi deleted file mode 100644 index 70926478ea7..00000000000 --- a/lispref/searching.texi +++ /dev/null @@ -1,1766 +0,0 @@ -@c -*-texinfo-*- -@c This is part of the GNU Emacs Lisp Reference Manual. -@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 -@chapter Searching and Matching -@cindex searching - - GNU Emacs provides two ways to search through a buffer for specified -text: exact string searches and regular expression searches. After a -regular expression search, you can examine the @dfn{match data} to -determine which text matched the whole regular expression or various -portions of it. - -@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. -* Match Data:: Finding out which part of the text matched, - after a string or regexp search. -* 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}. To search for changes in character -properties, see @ref{Property Search}. - -@node String Search -@section Searching for Strings -@cindex string search - - 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; 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 -@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 -line. Then @code{(search-forward "fox")} moves point after the last -letter of @samp{fox}: - -@example -@group ----------- Buffer: foo ---------- -@point{}The quick brown fox jumped over the lazy dog. ----------- Buffer: foo ---------- -@end group - -@group -(search-forward "fox") - @result{} 20 - ----------- Buffer: foo ---------- -The quick brown fox@point{} jumped over the lazy dog. ----------- Buffer: foo ---------- -@end group -@end example - -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 -@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 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 -function succeeds, moving point and returning its new value. Otherwise -the search fails, with results depending on the value of -@var{noerror}, as described above. -@end deffn - -@deffn Command search-backward string &optional limit noerror repeat -This function searches backward from point for @var{string}. It is -just like @code{search-forward} except that it searches backwards and -leaves point at the beginning of the match. -@end deffn - -@deffn Command word-search-forward string &optional limit noerror repeat -@c @cindex word search Redundant -This function searches forward from point for a ``word'' match for -@var{string}. If it finds a match, it sets point to the end of the -match found, and returns the new value of point. -@c Emacs 19 feature - -Word matching regards @var{string} as a sequence of words, disregarding -punctuation that separates them. It searches the buffer for the same -sequence of words. Each word must be distinct in the buffer (searching -for the word @samp{ball} does not match the word @samp{balls}), but the -details of punctuation and spacing are ignored (searching for @samp{ball -boy} does match @samp{ball. Boy!}). - -In this example, point is initially at the beginning of the buffer; the -search leaves it between the @samp{y} and the @samp{!}. - -@example -@group ----------- Buffer: foo ---------- -@point{}He said "Please! Find -the ball boy!" ----------- Buffer: foo ---------- -@end group - -@group -(word-search-forward "Please find the ball, boy.") - @result{} 35 - ----------- Buffer: foo ---------- -He said "Please! Find -the ball boy@point{}!" ----------- Buffer: foo ---------- -@end group -@end example - -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 -returns @code{nil} instead of signaling an error. If @var{noerror} is -neither @code{nil} nor @code{t}, it moves point to @var{limit} (or the -end of the accessible portion of the buffer) and returns @code{nil}. - -If @var{repeat} is non-@code{nil}, then the search is repeated that many -times. Point is positioned at the end of the last match. -@end deffn - -@deffn Command word-search-backward string &optional limit noerror repeat -This function searches backward from point for a word match to -@var{string}. This function is just like @code{word-search-forward} -except that it searches backward and normally leaves point at the -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 -@cindex regexp - - A @dfn{regular expression} (@dfn{regexp}, for short) is a pattern that -denotes a (possibly infinite) set of strings. Searching for matches for -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 regular expressions, developing - 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. -* Regexp Functions:: Functions for operating on regular expressions. -@end menu - -@node Syntax of Regexps -@subsection Syntax of Regular Expressions - - 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{$}, 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 -@samp{f} and no other string. (It does @emph{not} match the string -@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 -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} -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 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 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 @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 -possible. Thus, @samp{o*} matches any number of @samp{o}s (including no -@samp{o}s). - -@samp{*} always applies to the @emph{smallest} possible preceding -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 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. - -@strong{Warning:} Nested repetition operators can run for an -indefinitely long time, if they lead to ambiguous matching. For -example, trying to match the regular expression @samp{\(x+y*\)*a} -against the string @samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz} could -take hours before it ultimately fails. Emacs must try each way of -grouping the @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 -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 @samp{?} -@cindex @samp{?} in regexp -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 @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 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 alternative, by -writing the starting and ending characters with a @samp{-} between them. -Thus, @samp{[a-z]} matches any lower-case @acronym{ASCII} letter. -Ranges may be intermixed freely with individual characters, as in -@samp{[a-z$%.]}, which matches any lower case @acronym{ASCII} letter -or @samp{$}, @samp{%} or period. - -Note that the usual regexp special characters are not special inside a -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-@acronym{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-@acronym{ASCII} characters have codes -above octal 0377. However, the regular expression @code{"[^\000-\177]"} -does match all non-@acronym{ASCII} characters (see below regarding @samp{^}), -in both multibyte and unibyte representations, because only the -@acronym{ASCII} characters are excluded. - -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 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 -were first (in other words, @samp{-} and @samp{]} are not special there). - -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 @samp{^} -@cindex beginning of line in regexp -When matching a buffer, @samp{^} matches the empty string, but only at the -beginning of a line in the text being matched (or the beginning of the -accessible portion of the buffer). Otherwise it fails to match -anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at 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. - -For historical compatibility reasons, @samp{^} can be used only at the -beginning of the regular expression, or after @samp{\(}, @samp{\(?:} -or @samp{\|}. - -@item @samp{$} -@cindex @samp{$} in regexp -@cindex end of line in regexp -is similar to @samp{^} but matches only at the end of a line (or the -end of the accessible portion of the buffer). Thus, @samp{x+$} -matches a string of one @samp{x} or more at the end of a line. - -When matching a string instead of a buffer, @samp{$} matches at the end -of the string or before a newline character. - -For historical compatibility reasons, @samp{$} can be used only at the -end of the regular expression, or before @samp{\)} or @samp{\|}. - -@item @samp{\} -@cindex @samp{\} in regexp -has two functions: it quotes the special characters (including -@samp{\}), and it introduces additional special constructs. - -Because @samp{\} quotes special characters, @samp{\$} is a regular -expression that matches only @samp{$}, and @samp{\[} is a regular -expression that matches only @samp{[}, and so on. - -Note that @samp{\} also has special meaning in the read syntax of Lisp -strings (@pxref{String Type}), and must be quoted with @samp{\}. For -example, the regular expression that matches the @samp{\} character is -@samp{\\}. To write a Lisp string that contains the characters -@samp{\\}, Lisp syntax requires you to quote each @samp{\} with another -@samp{\}. Therefore, the read syntax for a regular expression matching -@samp{\} is @code{"\\\\"}.@refill -@end table - -@strong{Please note:} For historical compatibility, special characters -are treated as ordinary ones if they are in contexts where their special -meanings make no sense. For example, @samp{*foo} treats @samp{*} as -ordinary since there is no preceding expression on which the @samp{*} -can act. It is poor practice to depend on this behavior; quote the -special character anyway, regardless of where it appears.@refill - -As a @samp{\} is not special inside a character alternative, it can -never remove the special meaning of @samp{-} or @samp{]}. So you -should not quote these characters when they have no special meaning -either. This would not clarify anything, since backslashes can -legitimately precede these characters where they @emph{have} special -meaning, as in @samp{[^\]} (@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, -and what they mean: - -@table @samp -@item [:ascii:] -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 [: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 @acronym{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 @acronym{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 [:multibyte:] -This matches any multibyte character (@pxref{Text Representations}). -@item [:nonascii:] -This matches any non-@acronym{ASCII} character. -@item [:print:] -This matches printing characters---everything except @acronym{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 [: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}). -@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 @samp -@item \| -@cindex @samp{|} in regexp -@cindex regexp alternative -specifies an alternative. -Two regular expressions @var{a} and @var{b} with @samp{\|} in -between form an expression that matches anything that either @var{a} or -@var{b} matches.@refill - -Thus, @samp{foo\|bar} matches either @samp{foo} or @samp{bar} -but no other string.@refill - -@samp{\|} applies to the largest possible surrounding expressions. Only a -surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of -@samp{\|}.@refill - -If you need full backtracking capability to handle multiple uses of -@samp{\|}, 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 a 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 -@cindex @samp{)} in regexp -@cindex regexp grouping -is a grouping construct that serves three purposes: - -@enumerate -@item -To enclose a set of @samp{\|} alternatives for other operations. Thus, -the regular expression @samp{\(foo\|bar\)x} matches either @samp{foox} -or @samp{barx}. - -@item -To enclose a complicated expression for the postfix operators @samp{*}, -@samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches -@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 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 was assigned as a -second meaning to the same @samp{\( @dots{} \)} construct because, in -practice, 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 particularly useful for mechanically-constructed regular -expressions because they can be added automatically without altering the -numbering of any ordinary, non-shy groups. - -@item \(?@var{num}: @dots{} \) -is the @dfn{explicitly numbered group} construct. Normal groups get -their number implicitly, based on their position, which can be -inconvenient. This construct allows you to force a particular group -number. There is no particular restriction on the numbering, -e.g.@: you can have several groups with the same number in which case -the last one to match (i.e.@: the rightmost match) will win. -Implicitly numbered groups always get the smallest integer larger than -the one of any previous group. - -@item \@var{digit} -matches the same text that matched the @var{digit}th occurrence of a -grouping (@samp{\( @dots{} \)}) construct. - -In other words, after the end of a group, the matcher remembers the -beginning and end of the text matched by that group. Later on in the -regular expression you can use @samp{\} followed by @var{digit} to -match that same text, whatever it may have been. - -The strings matching the first nine grouping constructs appearing in -the entire regular expression passed to a search or matching function -are assigned numbers 1 through 9 in the order that the open -parentheses appear in the regular expression. So you can use -@samp{\1} through @samp{\9} to refer to the text matched by the -corresponding grouping constructs. - -For example, @samp{\(.*\)\1} matches any newline-free string that is -composed of two identical halves. The @samp{\(.*\)} matches the first -half, which may be anything, but the @samp{\1} that follows must match -the same exact text. - -If a @samp{\( @dots{} \)} construct matches more than once (which can -happen, for instance, if it is followed by @samp{*}), only the last -match is recorded. - -If a particular grouping construct in the regular expression was never -matched---for instance, if it appears inside of an alternative that -wasn't used, or inside of a repetition that repeated zero times---then -the corresponding @samp{\@var{digit}} construct never matches -anything. To use an artificial example,, @samp{\(foo\(b*\)\|lose\)\2} -cannot match @samp{lose}: the second alternative inside the larger -group matches it, but then @samp{\2} is undefined and can't match -anything. But it can match @samp{foobb}, because the first -alternative matches @samp{foob} and @samp{\2} matches @samp{b}. - -@item \w -@cindex @samp{\w} in regexp -matches any word-constituent character. The editor syntax table -determines which characters these are. @xref{Syntax Tables}. - -@item \W -@cindex @samp{\W} in regexp -matches any character that is not a word constituent. - -@item \s@var{code} -@cindex @samp{\s} in regexp -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. 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. For all, the beginning and end of the accessible portion of -the buffer are treated as if they were the actual beginning and end of -the buffer. - -@table @samp -@item \` -@cindex @samp{\`} in regexp -matches the empty string, but only at the beginning -of the buffer or string being matched against. - -@item \' -@cindex @samp{\'} in regexp -matches the empty string, but only at the end of -the buffer or string being matched against. - -@item \= -@cindex @samp{\=} in regexp -matches the empty string, but only at point. -(This construct is not defined when matching against a string.) - -@item \b -@cindex @samp{\b} in regexp -matches the empty string, but only at the beginning or -end of a word. Thus, @samp{\bfoo\b} matches any occurrence of -@samp{foo} as a separate word. @samp{\bballs?\b} matches -@samp{ball} or @samp{balls} as a separate word.@refill - -@samp{\b} matches at the beginning or end of the buffer (or string) -regardless of what text appears next to it. - -@item \B -@cindex @samp{\B} in regexp -matches the empty string, but @emph{not} at the beginning or -end of a word, nor at the beginning or end of the buffer (or string). - -@item \< -@cindex @samp{\<} in regexp -matches the empty string, but only at the beginning of a word. -@samp{\<} matches at the beginning of the buffer (or string) only if a -word-constituent character follows. - -@item \> -@cindex @samp{\>} in regexp -matches the empty string, but only at the end of a word. @samp{\>} -matches at the end of the buffer (or string) only if the contents end -with a word-constituent character. - -@item \_< -@cindex @samp{\_<} in regexp -matches the empty string, but only at the beginning of a symbol. A -symbol is a sequence of one or more word or symbol constituent -characters. @samp{\_<} matches at the beginning of the buffer (or -string) only if a symbol-constituent character follows. - -@item \_> -@cindex @samp{\_>} in regexp -matches the empty string, but only at the end of a symbol. @samp{\_>} -matches at the end of the buffer (or string) only if the contents end -with a symbol-constituent character. -@end table - -@kindex invalid-regexp - Not every string is a valid regular expression. For example, a string -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. - -@node Regexp Example -@comment node-name, next, previous, up -@subsection Complex Regexp Example - - Here is a complicated regexp which was formerly used by Emacs to -recognize the end of a sentence together with any whitespace that -follows. (Nowadays Emacs uses a similar but more complex default -regexp constructed by the function @code{sentence-end}. -@xref{Standard Regexps}.) - - First, we show the regexp as a string in Lisp syntax to distinguish -spaces from tab characters. The string constant begins and ends with a -double-quote. @samp{\"} stands for a double-quote as part of the -string, @samp{\\} for a backslash as part of the string, @samp{\t} for a -tab and @samp{\n} for a newline. - -@example -"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*" -@end example - -@noindent -In contrast, if you evaluate this string, you will see the following: - -@example -@group -"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*" - @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\|@ @ \\)[ -]*" -@end group -@end example - -@noindent -In this output, tab and newline appear as themselves. - - This regular expression contains four parts in succession and can be -deciphered as follows: - -@table @code -@item [.?!] -The first part of the pattern is a character alternative that matches -any one of three characters: period, question mark, and exclamation -mark. The match must begin with one of these three characters. (This -is one point where the new default regexp used by Emacs differs from -the old. The new value also allows some non-@acronym{ASCII} -characters that end a sentence without any following whitespace.) - -@item []\"')@}]* -The second part of the pattern matches any closing braces and quotation -marks, zero or more of them, that may follow the period, question mark -or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in -a string. The @samp{*} at the end indicates that the immediately -preceding regular expression (a character alternative, in this case) may be -repeated zero or more times. - -@item \\($\\|@ $\\|\t\\|@ @ \\) -The third part of the pattern matches the whitespace that follows the -end of a sentence: the end of a line (optionally with a space), or a -tab, or two spaces. The double backslashes mark the parentheses and -vertical bars as regular expression syntax; the parentheses delimit a -group and the vertical bars separate alternatives. The dollar sign is -used to match the end of a line. - -@item [ \t\n]* -Finally, the last part of the pattern matches any additional whitespace -beyond the minimum needed to end a sentence. -@end table - -@node Regexp Functions -@subsection Regular Expression Functions - - These functions operate on regular expressions. - -@defun regexp-quote string -This function returns a regular expression whose only exact match is -@var{string}. Using this regular expression in @code{looking-at} will -succeed only if the next characters in the buffer are @var{string}; -using it in a search function will succeed if the text being searched -contains @var{string}. - -This allows you to request an exact string match or search when calling -a function that wants a regular expression. - -@example -@group -(regexp-quote "^The cat$") - @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 in the list @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. If @var{paren} is @code{words}, then -that construct is additionally surrounded by @samp{\<} and @samp{\>}. - -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}. (This does not include -shy groups.) -@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 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 -text that is matched by the regular expression @var{regexp}. The -function skips over any amount of text that is not matched by -@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. 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; 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}: - -@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 -the @samp{t} of @samp{hat} and the newline). - -@example -@group ----------- Buffer: foo ---------- -I read "@point{}The cat in the hat -comes back" twice. ----------- Buffer: foo ---------- -@end group - -@group -(re-search-forward "[a-z]+" nil t 5) - @result{} 27 - ----------- Buffer: foo ---------- -I read "The cat in the hat@point{} -comes back" twice. ----------- Buffer: foo ---------- -@end group -@end example -@end deffn - -@deffn Command re-search-backward regexp &optional limit noerror repeat -This function searches backward in the current buffer for a string of -text that is matched by the regular expression @var{regexp}, leaving -point at the beginning of the first text found. - -This function is analogous to @code{re-search-forward}, but they are not -simple mirror images. @code{re-search-forward} finds the match whose -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 (and yet ends before the -starting point). 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 regular expressions from end to beginning. It's -not worth the trouble of implementing that. -@end deffn - -@defun string-match regexp string &optional start -This function returns the index of the start of the first match for -the regular expression @var{regexp} in @var{string}, or @code{nil} if -there is no match. If @var{start} is non-@code{nil}, the search starts -at that index in @var{string}. - -For example, - -@example -@group -(string-match - "quick" "The quick brown fox jumped quickly.") - @result{} 4 -@end group -@group -(string-match - "quick" "The quick brown fox jumped quickly." 8) - @result{} 27 -@end group -@end example - -@noindent -The index of the first character of the -string is 0, the index of the second character is 1, and so on. - -After this function returns, the index of the first character beyond -the match is available as @code{(match-end 0)}. @xref{Match Data}. - -@example -@group -(string-match - "quick" "The quick brown fox jumped quickly." 8) - @result{} 27 -@end group - -@group -(match-end 0) - @result{} 32 -@end group -@end example -@end defun - -@defun looking-at regexp -This function determines whether the text in the current buffer directly -following point matches the regular expression @var{regexp}. ``Directly -following'' means precisely that: the search is ``anchored'' and it can -succeed only starting with the first character following point. The -result is @code{t} if so, @code{nil} otherwise. - -This function does not move point, but it updates the match data, which -you can access using @code{match-beginning} and @code{match-end}. -@xref{Match Data}. - -In this example, point is located directly before the @samp{T}. If it -were anywhere else, the result would be @code{nil}. - -@example -@group ----------- Buffer: foo ---------- -I read "@point{}The cat in the hat -comes back" twice. ----------- Buffer: foo ---------- - -(looking-at "The cat in the hat$") - @result{} t -@end group -@end example -@end defun - -@defun looking-back regexp &optional limit -This function returns @code{t} if @var{regexp} matches text before -point, ending at point, and @code{nil} otherwise. - -Because regular expression matching works only going forward, this is -implemented by searching backwards from point for a match that ends at -point. That can be quite slow if it has to search a long distance. -You can bound the time required by specifying @var{limit}, which says -not to search before @var{limit}. In this case, the match that is -found must begin at or after @var{limit}. - -@example -@group ----------- Buffer: foo ---------- -I read "@point{}The cat in the hat -comes back" twice. ----------- Buffer: foo ---------- - -(looking-back "read \"" 3) - @result{} t -(looking-back "read \"" 4) - @result{} nil -@end group -@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 - - The usual regular expression functions do backtracking when necessary -to handle the @samp{\|} and repetition constructs, but they continue -this only until they find @emph{some} match. Then they succeed and -report the first match found. - - This section describes alternative search functions which perform the -full backtracking specified by the POSIX standard for regular expression -matching. They continue backtracking until they have tried all -possibilities and found all matches, so they can report the longest -match, as required by POSIX. This is much slower, so use these -functions only when you really need the longest match. - - The POSIX search and match functions do not properly support the -non-greedy repetition operators. This is because POSIX backtracking -conflicts with the semantics of non-greedy repetition. - -@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 -matching. -@end defun - -@defun posix-search-backward regexp &optional limit noerror repeat -This is like @code{re-search-backward} except that it performs the full -backtracking specified by the POSIX standard for regular expression -matching. -@end defun - -@defun posix-looking-at regexp -This is like @code{looking-at} except that it performs the full -backtracking specified by the POSIX standard for regular expression -matching. -@end defun - -@defun posix-string-match regexp string &optional start -This is like @code{string-match} except that it performs the full -backtracking specified by the POSIX standard for regular expression -matching. -@end defun - -@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 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 -search you wish to refer back to and the use of the match data. If you -can't avoid another intervening search, you must save and restore 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. -* 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 -@cindex replace matched text - - 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 -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} and make sure that the current buffer when you call -@code{replace-match} is the one in which you did the searching or -matching. 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 @code{replace-match} uses -the replacement text without case conversion; otherwise, it converts -the replacement text depending upon the capitalization of the text to -be replaced. If the original text is all upper case, this converts -the replacement text to upper case. If all words of the original text -are capitalized, this capitalizes all the words of the replacement -text. If all the words are one-letter and they are all upper case, -they are treated as capitalized words rather than all-upper-case -words. - -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{\(@dots{}\)}. -If the @var{n}th subexpression never matched, an empty string is substituted. - -@item @samp{\\} -@cindex @samp{\} in replacement -@samp{\\} stands for a single @samp{\} in the replacement text. -@end table - -These substitutions occur after case conversion, if any, -so the strings they substitute are never case-converted. - -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 - - This section explains how to use the match data to find out what was -matched by the last search or match operation, if it succeeded. - - You can ask about the entire matching text, or about a particular -parenthetical subexpression of a regular expression. The @var{count} -argument in the functions below specifies which. If @var{count} is -zero, you are asking about the entire match. If @var{count} is -positive, it specifies which subexpression you want. - - Recall that the subexpressions of a regular expression are those -expressions grouped with escaped parentheses, @samp{\(@dots{}\)}. The -@var{count}th subexpression is found by counting occurrences of -@samp{\(} from the beginning of the whole regular expression. The first -subexpression is numbered 1, the second 2, and so on. Only regular -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 -a failing search. - -@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, -or just the portion corresponding to the @var{count}th parenthetical -subexpression, if @var{count} is positive. - -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}. 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. - -The value is @code{nil} if @var{count} is out of range, or for a -subexpression inside a @samp{\|} alternative that wasn't used or a -repetition that repeated zero times. -@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 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{\|} -alternative that wasn't used or a repetition that repeated zero times. -@end defun - -@defun match-end count -This function is like @code{match-beginning} except that it returns the -position of the end of the match, rather than the position of the -beginning. -@end defun - - Here is an example of using the match data, with a comment showing the -positions within the text: - -@example -@group -(string-match "\\(qu\\)\\(ick\\)" - "The quick fox jumped quickly.") - ;0123456789 - @result{} 4 -@end group - -@group -(match-string 0 "The quick fox jumped quickly.") - @result{} "quick" -(match-string 1 "The quick fox jumped quickly.") - @result{} "qu" -(match-string 2 "The quick fox jumped quickly.") - @result{} "ick" -@end group - -@group -(match-beginning 1) ; @r{The beginning of the match} - @result{} 4 ; @r{with @samp{qu} is at index 4.} -@end group - -@group -(match-beginning 2) ; @r{The beginning of the match} - @result{} 6 ; @r{with @samp{ick} is at index 6.} -@end group - -@group -(match-end 1) ; @r{The end of the match} - @result{} 6 ; @r{with @samp{qu} is at index 6.} - -(match-end 2) ; @r{The end of the match} - @result{} 9 ; @r{with @samp{ick} is at index 9.} -@end group -@end example - - Here is another example. Point is initially located at the beginning -of the line. Searching moves point to between the space and the word -@samp{in}. The beginning of the entire match is at the 9th character of -the buffer (@samp{T}), and the beginning of the match for the first -subexpression is at the 13th character (@samp{c}). - -@example -@group -(list - (re-search-forward "The \\(cat \\)") - (match-beginning 0) - (match-beginning 1)) - @result{} (9 9 13) -@end group - -@group ----------- Buffer: foo ---------- -I read "The cat @point{}in the hat comes back" twice. - ^ ^ - 9 13 ----------- Buffer: foo ---------- -@end group -@end example - -@noindent -(In this case, the index returned is a buffer position; the first -character of the buffer counts as 1.) - -@node Entire Match Data -@subsection Accessing the Entire Match Data - - 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 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 -@tex -number {\mathsurround=0pt $2n$} -@end tex -corresponds to @code{(match-beginning @var{n})}; and -element -@ifnottex -number 2@var{n} + 1 -@end ifnottex -@tex -number {\mathsurround=0pt $2n+1$} -@end tex -corresponds to @code{(match-end @var{n})}. - -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, -@var{reuse} is destructively modified. @var{reuse} does not need to -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 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 -intended to access the match data for that search. - -@example -@group -(match-data) - @result{} (#<marker at 9 in foo> - #<marker at 17 in foo> - #<marker at 13 in foo> - #<marker at 17 in foo>) -@end group -@end example -@end defun - -@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 -will work.) - -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 - -@node Saving Match Data -@subsection Saving and Restoring the Match Data - - When you call a function that may do a search, you may need to save -and restore the match data around that call, if you want to preserve the -match data from an earlier search for later use. Here is an example -that shows the problem that arises if you fail to save the match data: - -@example -@group -(re-search-forward "The \\(cat \\)") - @result{} 48 -(foo) ; @r{Perhaps @code{foo} does} - ; @r{more searching.} -(match-end 0) - @result{} 61 ; @r{Unexpected result---not 48!} -@end group -@end example - - You can save and restore the match data with @code{save-match-data}: - -@defmac save-match-data body@dots{} -This macro executes @var{body}, saving and restoring the match -data around it. The return value is the value of the last form in -@var{body}. -@end defmac - - 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{Ok to change the original match data.} - (set-match-data data))) -@end group -@end example - - Emacs automatically saves and restores the match data when it runs -process filter functions (@pxref{Filter Functions}) and process -sentinels (@pxref{Sentinels}). - -@ignore - Here is a function which restores the match data provided the buffer -associated with it still exists. - -@smallexample -@group -(defun restore-match-data (data) -@c It is incorrect to split the first line of a doc string. -@c If there's a problem here, it should be solved in some other way. - "Restore the match data DATA unless the buffer is missing." - (catch 'foo - (let ((d data)) -@end group - (while d - (and (car d) - (null (marker-buffer (car d))) -@group - ;; @file{match-data} @r{buffer is deleted.} - (throw 'foo nil)) - (setq d (cdr d))) - (set-match-data data)))) -@end group -@end smallexample -@end ignore - -@node Search and Replace -@section Search and Replace -@cindex replacement after search -@cindex searching and replacing - - 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: - -@example -(while (re-search-forward "foo[ \t]+bar" nil t) - (replace-match "foobar")) -@end example - -@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 - - If you want to write a command along the lines of @code{query-replace}, -you can use @code{perform-replace} to do the work. - -@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}, 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 -@cindex standard regexps used in editing - - This section describes some variables that hold regular expressions -used for certain purposes in editing: - -@defvar page-delimiter -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 -match always starts at the beginning of a line; they should not use -@samp{^} to anchor the match. Most often, the paragraph commands do -check for a match only at the beginning of a line, which means that -@samp{^} would be superfluous. When there is a nonzero left margin, -they accept matches that start after the left margin. In that case, a -@samp{^} would be incorrect. However, a @samp{^} is harmless in modes -where a left margin is never used. - -@defvar paragraph-separate -This is the regular expression for recognizing the beginning of a line -that separates paragraphs. (If you change this, you may have to -change @code{paragraph-start} also.) The default value is -@w{@code{"[@ \t\f]*$"}}, which matches a line that consists entirely of -spaces, tabs, and form feeds (after its left margin). -@end defvar - -@defvar paragraph-start -This is the regular expression for recognizing the beginning of a line -that starts @emph{or} separates paragraphs. The default value is -@w{@code{"\f\\|[ \t]*$"}}, which matches a line containing only -whitespace or starting with a form feed (after its left margin). -@end defvar - -@defvar sentence-end -If non-@code{nil}, the value should be a regular expression describing -the end of a sentence, including the whitespace following the -sentence. (All paragraph boundaries also end sentences, regardless.) - -If the value is @code{nil}, the default, then the function -@code{sentence-end} has to construct the regexp. That is why you -should always call the function @code{sentence-end} to obtain the -regexp to be used to recognize the end of a sentence. -@end defvar - -@defun sentence-end -This function returns the value of the variable @code{sentence-end}, -if non-@code{nil}. Otherwise it returns a default value based on the -values of the variables @code{sentence-end-double-space} -(@pxref{Definition of sentence-end-double-space}), -@code{sentence-end-without-period} and -@code{sentence-end-without-space}. -@end defun - -@ignore - arch-tag: c2573ca2-18aa-4839-93b8-924043ef831f -@end ignore |