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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
177c0ea7 | 4 | @c Free Software Foundation, Inc. |
7015aca4 RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/searching | |
f9f59935 | 7 | @node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top |
7015aca4 RS |
8 | @chapter Searching and Matching |
9 | @cindex searching | |
10 | ||
11 | GNU Emacs provides two ways to search through a buffer for specified | |
12 | text: exact string searches and regular expression searches. After a | |
13 | regular expression search, you can examine the @dfn{match data} to | |
14 | determine which text matched the whole regular expression or various | |
15 | portions of it. | |
16 | ||
17 | @menu | |
18 | * String Search:: Search for an exact match. | |
19 | * Regular Expressions:: Describing classes of strings. | |
20 | * Regexp Search:: Searching for a match for a regexp. | |
22697dac | 21 | * POSIX Regexps:: Searching POSIX-style for the longest match. |
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22 | * Search and Replace:: Internals of @code{query-replace}. |
23 | * Match Data:: Finding out which part of the text matched | |
24 | various parts of a regexp, after regexp search. | |
25 | * Searching and Case:: Case-independent or case-significant searching. | |
26 | * Standard Regexps:: Useful regexps for finding sentences, pages,... | |
27 | @end menu | |
28 | ||
29 | The @samp{skip-chars@dots{}} functions also perform a kind of searching. | |
30 | @xref{Skipping Characters}. | |
31 | ||
32 | @node String Search | |
33 | @section Searching for Strings | |
34 | @cindex string search | |
35 | ||
36 | These are the primitive functions for searching through the text in a | |
37 | buffer. They are meant for use in programs, but you may call them | |
8241495d RS |
38 | interactively. If you do so, they prompt for the search string; the |
39 | arguments @var{limit} and @var{noerror} are @code{nil}, and @var{repeat} | |
40 | is 1. | |
7015aca4 | 41 | |
f9f59935 RS |
42 | These search functions convert the search string to multibyte if the |
43 | buffer is multibyte; they convert the search string to unibyte if the | |
44 | buffer is unibyte. @xref{Text Representations}. | |
45 | ||
7015aca4 | 46 | @deffn Command search-forward string &optional limit noerror repeat |
f9f59935 | 47 | This function searches forward from point for an exact match for |
7015aca4 RS |
48 | @var{string}. If successful, it sets point to the end of the occurrence |
49 | found, and returns the new value of point. If no match is found, the | |
50 | value and side effects depend on @var{noerror} (see below). | |
51 | @c Emacs 19 feature | |
52 | ||
f9f59935 | 53 | In the following example, point is initially at the beginning of the |
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54 | line. Then @code{(search-forward "fox")} moves point after the last |
55 | letter of @samp{fox}: | |
56 | ||
57 | @example | |
58 | @group | |
59 | ---------- Buffer: foo ---------- | |
60 | @point{}The quick brown fox jumped over the lazy dog. | |
61 | ---------- Buffer: foo ---------- | |
62 | @end group | |
63 | ||
64 | @group | |
65 | (search-forward "fox") | |
66 | @result{} 20 | |
67 | ||
68 | ---------- Buffer: foo ---------- | |
69 | The quick brown fox@point{} jumped over the lazy dog. | |
70 | ---------- Buffer: foo ---------- | |
71 | @end group | |
72 | @end example | |
73 | ||
f9f59935 | 74 | The argument @var{limit} specifies the upper bound to the search. (It |
7015aca4 RS |
75 | must be a position in the current buffer.) No match extending after |
76 | that position is accepted. If @var{limit} is omitted or @code{nil}, it | |
77 | defaults to the end of the accessible portion of the buffer. | |
78 | ||
79 | @kindex search-failed | |
f9f59935 | 80 | What happens when the search fails depends on the value of |
7015aca4 RS |
81 | @var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed} |
82 | error is signaled. If @var{noerror} is @code{t}, @code{search-forward} | |
83 | returns @code{nil} and does nothing. If @var{noerror} is neither | |
84 | @code{nil} nor @code{t}, then @code{search-forward} moves point to the | |
f9f59935 RS |
85 | upper bound and returns @code{nil}. (It would be more consistent now to |
86 | return the new position of point in that case, but some existing | |
87 | programs may depend on a value of @code{nil}.) | |
7015aca4 | 88 | |
61cfa852 RS |
89 | If @var{repeat} is supplied (it must be a positive number), then the |
90 | search is repeated that many times (each time starting at the end of the | |
91 | previous time's match). If these successive searches succeed, the | |
92 | function succeeds, moving point and returning its new value. Otherwise | |
3ab8acb9 | 93 | the search fails, leaving point where it started. |
7015aca4 RS |
94 | @end deffn |
95 | ||
96 | @deffn Command search-backward string &optional limit noerror repeat | |
97 | This function searches backward from point for @var{string}. It is | |
98 | just like @code{search-forward} except that it searches backwards and | |
99 | leaves point at the beginning of the match. | |
100 | @end deffn | |
101 | ||
102 | @deffn Command word-search-forward string &optional limit noerror repeat | |
103 | @cindex word search | |
104 | This function searches forward from point for a ``word'' match for | |
105 | @var{string}. If it finds a match, it sets point to the end of the | |
106 | match found, and returns the new value of point. | |
107 | @c Emacs 19 feature | |
108 | ||
109 | Word matching regards @var{string} as a sequence of words, disregarding | |
110 | punctuation that separates them. It searches the buffer for the same | |
111 | sequence of words. Each word must be distinct in the buffer (searching | |
112 | for the word @samp{ball} does not match the word @samp{balls}), but the | |
113 | details of punctuation and spacing are ignored (searching for @samp{ball | |
114 | boy} does match @samp{ball. Boy!}). | |
115 | ||
116 | In this example, point is initially at the beginning of the buffer; the | |
117 | search leaves it between the @samp{y} and the @samp{!}. | |
118 | ||
119 | @example | |
120 | @group | |
121 | ---------- Buffer: foo ---------- | |
122 | @point{}He said "Please! Find | |
123 | the ball boy!" | |
124 | ---------- Buffer: foo ---------- | |
125 | @end group | |
126 | ||
127 | @group | |
128 | (word-search-forward "Please find the ball, boy.") | |
129 | @result{} 35 | |
130 | ||
131 | ---------- Buffer: foo ---------- | |
132 | He said "Please! Find | |
133 | the ball boy@point{}!" | |
134 | ---------- Buffer: foo ---------- | |
135 | @end group | |
136 | @end example | |
137 | ||
138 | If @var{limit} is non-@code{nil} (it must be a position in the current | |
139 | buffer), then it is the upper bound to the search. The match found must | |
140 | not extend after that position. | |
141 | ||
142 | If @var{noerror} is @code{nil}, then @code{word-search-forward} signals | |
143 | an error if the search fails. If @var{noerror} is @code{t}, then it | |
144 | returns @code{nil} instead of signaling an error. If @var{noerror} is | |
145 | neither @code{nil} nor @code{t}, it moves point to @var{limit} (or the | |
146 | end of the buffer) and returns @code{nil}. | |
147 | ||
148 | If @var{repeat} is non-@code{nil}, then the search is repeated that many | |
149 | times. Point is positioned at the end of the last match. | |
150 | @end deffn | |
151 | ||
152 | @deffn Command word-search-backward string &optional limit noerror repeat | |
153 | This function searches backward from point for a word match to | |
154 | @var{string}. This function is just like @code{word-search-forward} | |
155 | except that it searches backward and normally leaves point at the | |
156 | beginning of the match. | |
157 | @end deffn | |
158 | ||
159 | @node Regular Expressions | |
160 | @section Regular Expressions | |
161 | @cindex regular expression | |
162 | @cindex regexp | |
163 | ||
164 | A @dfn{regular expression} (@dfn{regexp}, for short) is a pattern that | |
165 | denotes a (possibly infinite) set of strings. Searching for matches for | |
166 | a regexp is a very powerful operation. This section explains how to write | |
167 | regexps; the following section says how to search for them. | |
168 | ||
169 | @menu | |
170 | * Syntax of Regexps:: Rules for writing regular expressions. | |
8241495d | 171 | * Regexp Functions:: Functions for operating on regular expressions. |
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172 | * Regexp Example:: Illustrates regular expression syntax. |
173 | @end menu | |
174 | ||
175 | @node Syntax of Regexps | |
176 | @subsection Syntax of Regular Expressions | |
177 | ||
61cfa852 RS |
178 | Regular expressions have a syntax in which a few characters are |
179 | special constructs and the rest are @dfn{ordinary}. An ordinary | |
180 | character is a simple regular expression that matches that character and | |
181 | nothing else. The special characters are @samp{.}, @samp{*}, @samp{+}, | |
182 | @samp{?}, @samp{[}, @samp{]}, @samp{^}, @samp{$}, and @samp{\}; no new | |
183 | special characters will be defined in the future. Any other character | |
184 | appearing in a regular expression is ordinary, unless a @samp{\} | |
185 | precedes it. | |
7015aca4 | 186 | |
8241495d | 187 | For example, @samp{f} is not a special character, so it is ordinary, and |
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188 | therefore @samp{f} is a regular expression that matches the string |
189 | @samp{f} and no other string. (It does @emph{not} match the string | |
8241495d RS |
190 | @samp{fg}, but it does match a @emph{part} of that string.) Likewise, |
191 | @samp{o} is a regular expression that matches only @samp{o}.@refill | |
7015aca4 | 192 | |
8241495d | 193 | Any two regular expressions @var{a} and @var{b} can be concatenated. The |
61cfa852 | 194 | result is a regular expression that matches a string if @var{a} matches |
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195 | some amount of the beginning of that string and @var{b} matches the rest of |
196 | the string.@refill | |
197 | ||
8241495d | 198 | As a simple example, we can concatenate the regular expressions @samp{f} |
7015aca4 RS |
199 | and @samp{o} to get the regular expression @samp{fo}, which matches only |
200 | the string @samp{fo}. Still trivial. To do something more powerful, you | |
8241495d RS |
201 | need to use one of the special regular expression constructs. |
202 | ||
203 | @menu | |
204 | * Regexp Special:: Special characters in regular expressions. | |
205 | * Char Classes:: Character classes used in regular expressions. | |
206 | * Regexp Backslash:: Backslash-sequences in regular expressions. | |
207 | @end menu | |
208 | ||
209 | @node Regexp Special | |
210 | @subsubsection Special Characters in Regular Expressions | |
211 | ||
212 | Here is a list of the characters that are special in a regular | |
213 | expression. | |
7015aca4 | 214 | |
7dd3d99f | 215 | @need 800 |
969fe9b5 RS |
216 | @table @asis |
217 | @item @samp{.}@: @r{(Period)} | |
7015aca4 RS |
218 | @cindex @samp{.} in regexp |
219 | is a special character that matches any single character except a newline. | |
220 | Using concatenation, we can make regular expressions like @samp{a.b}, which | |
221 | matches any three-character string that begins with @samp{a} and ends with | |
222 | @samp{b}.@refill | |
223 | ||
969fe9b5 | 224 | @item @samp{*} |
7015aca4 | 225 | @cindex @samp{*} in regexp |
1cd71ce0 RS |
226 | is not a construct by itself; it is a postfix operator that means to |
227 | match the preceding regular expression repetitively as many times as | |
228 | possible. Thus, @samp{o*} matches any number of @samp{o}s (including no | |
229 | @samp{o}s). | |
7015aca4 RS |
230 | |
231 | @samp{*} always applies to the @emph{smallest} possible preceding | |
1cd71ce0 RS |
232 | expression. Thus, @samp{fo*} has a repeating @samp{o}, not a repeating |
233 | @samp{fo}. It matches @samp{f}, @samp{fo}, @samp{foo}, and so on. | |
7015aca4 | 234 | |
f9f59935 RS |
235 | The matcher processes a @samp{*} construct by matching, immediately, as |
236 | many repetitions as can be found. Then it continues with the rest of | |
237 | the pattern. If that fails, backtracking occurs, discarding some of the | |
238 | matches of the @samp{*}-modified construct in the hope that that will | |
239 | make it possible to match the rest of the pattern. For example, in | |
240 | matching @samp{ca*ar} against the string @samp{caaar}, the @samp{a*} | |
241 | first tries to match all three @samp{a}s; but the rest of the pattern is | |
7015aca4 | 242 | @samp{ar} and there is only @samp{r} left to match, so this try fails. |
f9f59935 RS |
243 | The next alternative is for @samp{a*} to match only two @samp{a}s. With |
244 | this choice, the rest of the regexp matches successfully.@refill | |
7015aca4 | 245 | |
73031603 | 246 | Nested repetition operators can be extremely slow if they specify |
22697dac | 247 | backtracking loops. For example, it could take hours for the regular |
a9f0a989 RS |
248 | expression @samp{\(x+y*\)*a} to try to match the sequence |
249 | @samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz}, before it ultimately fails. | |
250 | The slowness is because Emacs must try each imaginable way of grouping | |
1911e6e5 | 251 | the 35 @samp{x}s before concluding that none of them can work. To make |
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252 | sure your regular expressions run fast, check nested repetitions |
253 | carefully. | |
73031603 | 254 | |
969fe9b5 | 255 | @item @samp{+} |
7015aca4 | 256 | @cindex @samp{+} in regexp |
1cd71ce0 RS |
257 | is a postfix operator, similar to @samp{*} except that it must match |
258 | the preceding expression at least once. So, for example, @samp{ca+r} | |
7015aca4 RS |
259 | matches the strings @samp{car} and @samp{caaaar} but not the string |
260 | @samp{cr}, whereas @samp{ca*r} matches all three strings. | |
261 | ||
969fe9b5 | 262 | @item @samp{?} |
7015aca4 | 263 | @cindex @samp{?} in regexp |
f9f59935 | 264 | is a postfix operator, similar to @samp{*} except that it must match the |
1cd71ce0 RS |
265 | preceding expression either once or not at all. For example, |
266 | @samp{ca?r} matches @samp{car} or @samp{cr}; nothing else. | |
7015aca4 | 267 | |
c082a348 RS |
268 | @item @samp{*?}, @samp{+?}, @samp{??} |
269 | These are ``non-greedy'' variants of the operators @samp{*}, @samp{+} | |
270 | and @samp{?}. Where those operators match the largest possible | |
271 | substring (consistent with matching the entire containing expression), | |
272 | the non-greedy variants match the smallest possible substring | |
273 | (consistent with matching the entire containing expression). | |
274 | ||
275 | For example, the regular expression @samp{c[ad]*a} when applied to the | |
276 | string @samp{cdaaada} matches the whole string; but the regular | |
277 | expression @samp{c[ad]*?a}, applied to that same string, matches just | |
278 | @samp{cda}. (The smallest possible match here for @samp{[ad]*?} that | |
279 | permits the whole expression to match is @samp{d}.) | |
280 | ||
969fe9b5 RS |
281 | @item @samp{[ @dots{} ]} |
282 | @cindex character alternative (in regexp) | |
7015aca4 RS |
283 | @cindex @samp{[} in regexp |
284 | @cindex @samp{]} in regexp | |
969fe9b5 RS |
285 | is a @dfn{character alternative}, which begins with @samp{[} and is |
286 | terminated by @samp{]}. In the simplest case, the characters between | |
287 | the two brackets are what this character alternative can match. | |
1cd71ce0 RS |
288 | |
289 | Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and | |
290 | @samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s | |
291 | (including the empty string), from which it follows that @samp{c[ad]*r} | |
292 | matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc. | |
293 | ||
969fe9b5 RS |
294 | You can also include character ranges in a character alternative, by |
295 | writing the starting and ending characters with a @samp{-} between them. | |
ad800164 | 296 | Thus, @samp{[a-z]} matches any lower-case @acronym{ASCII} letter. Ranges may be |
1cd71ce0 | 297 | intermixed freely with individual characters, as in @samp{[a-z$%.]}, |
ad800164 | 298 | which matches any lower case @acronym{ASCII} letter or @samp{$}, @samp{%} or |
1cd71ce0 RS |
299 | period. |
300 | ||
301 | Note that the usual regexp special characters are not special inside a | |
86494bd5 | 302 | character alternative. A completely different set of characters is |
969fe9b5 | 303 | special inside character alternatives: @samp{]}, @samp{-} and @samp{^}. |
1cd71ce0 | 304 | |
969fe9b5 RS |
305 | To include a @samp{]} in a character alternative, you must make it the |
306 | first character. For example, @samp{[]a]} matches @samp{]} or @samp{a}. | |
307 | To include a @samp{-}, write @samp{-} as the first or last character of | |
308 | the character alternative, or put it after a range. Thus, @samp{[]-]} | |
309 | matches both @samp{]} and @samp{-}. | |
7015aca4 | 310 | |
969fe9b5 RS |
311 | To include @samp{^} in a character alternative, put it anywhere but at |
312 | the beginning. | |
7015aca4 | 313 | |
8f17d892 RS |
314 | The beginning and end of a range of multibyte characters must be in |
315 | the same character set (@pxref{Character Sets}). Thus, | |
316 | @code{"[\x8e0-\x97c]"} is invalid because character 0x8e0 (@samp{a} | |
317 | with grave accent) is in the Emacs character set for Latin-1 but the | |
318 | character 0x97c (@samp{u} with diaeresis) is in the Emacs character | |
319 | set for Latin-2. (We use Lisp string syntax to write that example, | |
320 | and a few others in the next few paragraphs, in order to include hex | |
321 | escape sequences in them.) | |
6cc089d2 DL |
322 | |
323 | If a range starts with a unibyte character @var{c} and ends with a | |
324 | multibyte character @var{c2}, the range is divided into two parts: one | |
325 | is @samp{@var{c}..?\377}, the other is @samp{@var{c1}..@var{c2}}, where | |
326 | @var{c1} is the first character of the charset to which @var{c2} | |
327 | belongs. | |
177c0ea7 | 328 | |
ad800164 | 329 | You cannot always match all non-@acronym{ASCII} characters with the regular |
8f17d892 | 330 | expression @code{"[\200-\377]"}. This works when searching a unibyte |
8241495d | 331 | buffer or string (@pxref{Text Representations}), but not in a multibyte |
ad800164 | 332 | buffer or string, because many non-@acronym{ASCII} characters have codes |
8f17d892 | 333 | above octal 0377. However, the regular expression @code{"[^\000-\177]"} |
ad800164 | 334 | does match all non-@acronym{ASCII} characters (see below regarding @samp{^}), |
8241495d | 335 | in both multibyte and unibyte representations, because only the |
ad800164 | 336 | @acronym{ASCII} characters are excluded. |
8241495d RS |
337 | |
338 | Starting in Emacs 21, a character alternative can also specify named | |
339 | character classes (@pxref{Char Classes}). This is a POSIX feature whose | |
340 | syntax is @samp{[:@var{class}:]}. Using a character class is equivalent | |
341 | to mentioning each of the characters in that class; but the latter is | |
342 | not feasible in practice, since some classes include thousands of | |
343 | different characters. | |
344 | ||
969fe9b5 | 345 | @item @samp{[^ @dots{} ]} |
7015aca4 | 346 | @cindex @samp{^} in regexp |
969fe9b5 | 347 | @samp{[^} begins a @dfn{complemented character alternative}, which matches any |
1cd71ce0 RS |
348 | character except the ones specified. Thus, @samp{[^a-z0-9A-Z]} matches |
349 | all characters @emph{except} letters and digits. | |
7015aca4 | 350 | |
969fe9b5 | 351 | @samp{^} is not special in a character alternative unless it is the first |
7015aca4 | 352 | character. The character following the @samp{^} is treated as if it |
1cd71ce0 | 353 | were first (in other words, @samp{-} and @samp{]} are not special there). |
7015aca4 | 354 | |
969fe9b5 | 355 | A complemented character alternative can match a newline, unless newline is |
1cd71ce0 RS |
356 | mentioned as one of the characters not to match. This is in contrast to |
357 | the handling of regexps in programs such as @code{grep}. | |
7015aca4 | 358 | |
969fe9b5 | 359 | @item @samp{^} |
7015aca4 | 360 | @cindex beginning of line in regexp |
61cfa852 RS |
361 | is a special character that matches the empty string, but only at the |
362 | beginning of a line in the text being matched. Otherwise it fails to | |
363 | match anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at | |
364 | the beginning of a line. | |
7015aca4 | 365 | |
61cfa852 | 366 | When matching a string instead of a buffer, @samp{^} matches at the |
8f17d892 | 367 | beginning of the string or after a newline character. |
7015aca4 | 368 | |
8241495d RS |
369 | For historical compatibility reasons, @samp{^} can be used only at the |
370 | beginning of the regular expression, or after @samp{\(} or @samp{\|}. | |
371 | ||
969fe9b5 | 372 | @item @samp{$} |
7015aca4 | 373 | @cindex @samp{$} in regexp |
8241495d | 374 | @cindex end of line in regexp |
7015aca4 RS |
375 | is similar to @samp{^} but matches only at the end of a line. Thus, |
376 | @samp{x+$} matches a string of one @samp{x} or more at the end of a line. | |
377 | ||
61cfa852 | 378 | When matching a string instead of a buffer, @samp{$} matches at the end |
8f17d892 | 379 | of the string or before a newline character. |
7015aca4 | 380 | |
8241495d RS |
381 | For historical compatibility reasons, @samp{$} can be used only at the |
382 | end of the regular expression, or before @samp{\)} or @samp{\|}. | |
383 | ||
969fe9b5 | 384 | @item @samp{\} |
7015aca4 RS |
385 | @cindex @samp{\} in regexp |
386 | has two functions: it quotes the special characters (including | |
387 | @samp{\}), and it introduces additional special constructs. | |
388 | ||
389 | Because @samp{\} quotes special characters, @samp{\$} is a regular | |
61cfa852 RS |
390 | expression that matches only @samp{$}, and @samp{\[} is a regular |
391 | expression that matches only @samp{[}, and so on. | |
7015aca4 RS |
392 | |
393 | Note that @samp{\} also has special meaning in the read syntax of Lisp | |
394 | strings (@pxref{String Type}), and must be quoted with @samp{\}. For | |
395 | example, the regular expression that matches the @samp{\} character is | |
396 | @samp{\\}. To write a Lisp string that contains the characters | |
397 | @samp{\\}, Lisp syntax requires you to quote each @samp{\} with another | |
398 | @samp{\}. Therefore, the read syntax for a regular expression matching | |
399 | @samp{\} is @code{"\\\\"}.@refill | |
400 | @end table | |
401 | ||
b22f3a19 | 402 | @strong{Please note:} For historical compatibility, special characters |
7015aca4 RS |
403 | are treated as ordinary ones if they are in contexts where their special |
404 | meanings make no sense. For example, @samp{*foo} treats @samp{*} as | |
405 | ordinary since there is no preceding expression on which the @samp{*} | |
61cfa852 RS |
406 | can act. It is poor practice to depend on this behavior; quote the |
407 | special character anyway, regardless of where it appears.@refill | |
7015aca4 | 408 | |
8241495d RS |
409 | @node Char Classes |
410 | @subsubsection Character Classes | |
411 | @cindex character classes in regexp | |
412 | ||
413 | Here is a table of the classes you can use in a character alternative, | |
414 | in Emacs 21, and what they mean: | |
415 | ||
416 | @table @samp | |
417 | @item [:ascii:] | |
ad800164 | 418 | This matches any @acronym{ASCII} (unibyte) character. |
8241495d RS |
419 | @item [:alnum:] |
420 | This matches any letter or digit. (At present, for multibyte | |
421 | characters, it matches anything that has word syntax.) | |
422 | @item [:alpha:] | |
423 | This matches any letter. (At present, for multibyte characters, it | |
424 | matches anything that has word syntax.) | |
425 | @item [:blank:] | |
426 | This matches space and tab only. | |
427 | @item [:cntrl:] | |
ad800164 | 428 | This matches any @acronym{ASCII} control character. |
8241495d RS |
429 | @item [:digit:] |
430 | This matches @samp{0} through @samp{9}. Thus, @samp{[-+[:digit:]]} | |
431 | matches any digit, as well as @samp{+} and @samp{-}. | |
432 | @item [:graph:] | |
ad800164 | 433 | This matches graphic characters---everything except @acronym{ASCII} control |
75708135 | 434 | characters, space, and the delete character. |
8241495d RS |
435 | @item [:lower:] |
436 | This matches any lower-case letter, as determined by | |
437 | the current case table (@pxref{Case Tables}). | |
438 | @item [:nonascii:] | |
ad800164 | 439 | This matches any non-@acronym{ASCII} (multibyte) character. |
8241495d | 440 | @item [:print:] |
ad800164 | 441 | This matches printing characters---everything except @acronym{ASCII} control |
caccdcbb | 442 | characters and the delete character. |
8241495d RS |
443 | @item [:punct:] |
444 | This matches any punctuation character. (At present, for multibyte | |
445 | characters, it matches anything that has non-word syntax.) | |
446 | @item [:space:] | |
447 | This matches any character that has whitespace syntax | |
448 | (@pxref{Syntax Class Table}). | |
449 | @item [:upper:] | |
450 | This matches any upper-case letter, as determined by | |
451 | the current case table (@pxref{Case Tables}). | |
452 | @item [:word:] | |
453 | This matches any character that has word syntax (@pxref{Syntax Class | |
454 | Table}). | |
455 | @item [:xdigit:] | |
456 | This matches the hexadecimal digits: @samp{0} through @samp{9}, @samp{a} | |
457 | through @samp{f} and @samp{A} through @samp{F}. | |
458 | @end table | |
459 | ||
460 | @node Regexp Backslash | |
461 | @subsubsection Backslash Constructs in Regular Expressions | |
462 | ||
463 | For the most part, @samp{\} followed by any character matches only | |
464 | that character. However, there are several exceptions: certain | |
465 | two-character sequences starting with @samp{\} that have special | |
466 | meanings. (The character after the @samp{\} in such a sequence is | |
467 | always ordinary when used on its own.) Here is a table of the special | |
468 | @samp{\} constructs. | |
7015aca4 | 469 | |
969fe9b5 | 470 | @table @samp |
7015aca4 RS |
471 | @item \| |
472 | @cindex @samp{|} in regexp | |
473 | @cindex regexp alternative | |
474 | specifies an alternative. | |
475 | Two regular expressions @var{a} and @var{b} with @samp{\|} in | |
476 | between form an expression that matches anything that either @var{a} or | |
477 | @var{b} matches.@refill | |
478 | ||
479 | Thus, @samp{foo\|bar} matches either @samp{foo} or @samp{bar} | |
480 | but no other string.@refill | |
481 | ||
482 | @samp{\|} applies to the largest possible surrounding expressions. Only a | |
483 | surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of | |
484 | @samp{\|}.@refill | |
485 | ||
01913af2 RS |
486 | If you need full backtracking capability to handle multiple uses of |
487 | @samp{\|}, use the POSIX regular expression functions (@pxref{POSIX | |
488 | Regexps}). | |
7015aca4 | 489 | |
2d06696f RS |
490 | @item \@{@var{m}\@} |
491 | is a postfix operator that repeats the previous pattern exactly @var{m} | |
492 | times. Thus, @samp{x\@{5\@}} matches the string @samp{xxxxx} | |
493 | and nothing else. @samp{c[ad]\@{3\@}r} matches string such as | |
494 | @samp{caaar}, @samp{cdddr}, @samp{cadar}, and so on. | |
495 | ||
496 | @item \@{@var{m},@var{n}\@} | |
497 | is more general postfix operator that specifies repetition with a | |
498 | minimum of @var{m} repeats and a maximum of @var{n} repeats. If @var{m} | |
499 | is omitted, the minimum is 0; if @var{n} is omitted, there is no | |
500 | maximum. | |
501 | ||
502 | For example, @samp{c[ad]\@{1,2\@}r} matches the strings @samp{car}, | |
503 | @samp{cdr}, @samp{caar}, @samp{cadr}, @samp{cdar}, and @samp{cddr}, and | |
504 | nothing else.@* | |
505 | @samp{\@{0,1\@}} or @samp{\@{,1\@}} is equivalent to @samp{?}. @* | |
506 | @samp{\@{0,\@}} or @samp{\@{,\@}} is equivalent to @samp{*}. @* | |
507 | @samp{\@{1,\@}} is equivalent to @samp{+}. | |
508 | ||
7015aca4 RS |
509 | @item \( @dots{} \) |
510 | @cindex @samp{(} in regexp | |
511 | @cindex @samp{)} in regexp | |
512 | @cindex regexp grouping | |
513 | is a grouping construct that serves three purposes: | |
514 | ||
515 | @enumerate | |
516 | @item | |
9e2b495b RS |
517 | To enclose a set of @samp{\|} alternatives for other operations. Thus, |
518 | the regular expression @samp{\(foo\|bar\)x} matches either @samp{foox} | |
519 | or @samp{barx}. | |
7015aca4 RS |
520 | |
521 | @item | |
1cd71ce0 RS |
522 | To enclose a complicated expression for the postfix operators @samp{*}, |
523 | @samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches | |
a9f0a989 RS |
524 | @samp{ba}, @samp{bana}, @samp{banana}, @samp{bananana}, etc., with any |
525 | number (zero or more) of @samp{na} strings. | |
7015aca4 RS |
526 | |
527 | @item | |
2d06696f RS |
528 | To record a matched substring for future reference with |
529 | @samp{\@var{digit}} (see below). | |
7015aca4 RS |
530 | @end enumerate |
531 | ||
532 | This last application is not a consequence of the idea of a | |
2d06696f RS |
533 | parenthetical grouping; it is a separate feature that was assigned as a |
534 | second meaning to the same @samp{\( @dots{} \)} construct because, in | |
a39c2e0d | 535 | practice, there was usually no conflict between the two meanings. But |
2d06696f RS |
536 | occasionally there is a conflict, and that led to the introduction of |
537 | shy groups. | |
538 | ||
539 | @item \(?: @dots{} \) | |
540 | is the @dfn{shy group} construct. A shy group serves the first two | |
541 | purposes of an ordinary group (controlling the nesting of other | |
542 | operators), but it does not get a number, so you cannot refer back to | |
543 | its value with @samp{\@var{digit}}. | |
544 | ||
545 | Shy groups are particulary useful for mechanically-constructed regular | |
546 | expressions because they can be added automatically without altering the | |
547 | numbering of any ordinary, non-shy groups. | |
7015aca4 RS |
548 | |
549 | @item \@var{digit} | |
61cfa852 | 550 | matches the same text that matched the @var{digit}th occurrence of a |
a5d0a32e | 551 | grouping (@samp{\( @dots{} \)}) construct. |
7015aca4 | 552 | |
a5d0a32e RS |
553 | In other words, after the end of a group, the matcher remembers the |
554 | beginning and end of the text matched by that group. Later on in the | |
555 | regular expression you can use @samp{\} followed by @var{digit} to | |
556 | match that same text, whatever it may have been. | |
7015aca4 | 557 | |
a5d0a32e RS |
558 | The strings matching the first nine grouping constructs appearing in |
559 | the entire regular expression passed to a search or matching function | |
560 | are assigned numbers 1 through 9 in the order that the open | |
561 | parentheses appear in the regular expression. So you can use | |
562 | @samp{\1} through @samp{\9} to refer to the text matched by the | |
563 | corresponding grouping constructs. | |
7015aca4 RS |
564 | |
565 | For example, @samp{\(.*\)\1} matches any newline-free string that is | |
566 | composed of two identical halves. The @samp{\(.*\)} matches the first | |
567 | half, which may be anything, but the @samp{\1} that follows must match | |
568 | the same exact text. | |
569 | ||
a5d0a32e RS |
570 | If a particular grouping construct in the regular expression was never |
571 | matched---for instance, if it appears inside of an alternative that | |
572 | wasn't used, or inside of a repetition that repeated zero times---then | |
573 | the corresponding @samp{\@var{digit}} construct never matches | |
574 | anything. To use an artificial example,, @samp{\(foo\(b*\)\|lose\)\2} | |
575 | cannot match @samp{lose}: the second alternative inside the larger | |
576 | group matches it, but then @samp{\2} is undefined and can't match | |
577 | anything. But it can match @samp{foobb}, because the first | |
578 | alternative matches @samp{foob} and @samp{\2} matches @samp{b}. | |
579 | ||
7015aca4 RS |
580 | @item \w |
581 | @cindex @samp{\w} in regexp | |
582 | matches any word-constituent character. The editor syntax table | |
583 | determines which characters these are. @xref{Syntax Tables}. | |
584 | ||
585 | @item \W | |
586 | @cindex @samp{\W} in regexp | |
61cfa852 | 587 | matches any character that is not a word constituent. |
7015aca4 RS |
588 | |
589 | @item \s@var{code} | |
590 | @cindex @samp{\s} in regexp | |
591 | matches any character whose syntax is @var{code}. Here @var{code} is a | |
61cfa852 | 592 | character that represents a syntax code: thus, @samp{w} for word |
7015aca4 | 593 | constituent, @samp{-} for whitespace, @samp{(} for open parenthesis, |
f9f59935 RS |
594 | etc. To represent whitespace syntax, use either @samp{-} or a space |
595 | character. @xref{Syntax Class Table}, for a list of syntax codes and | |
596 | the characters that stand for them. | |
7015aca4 RS |
597 | |
598 | @item \S@var{code} | |
599 | @cindex @samp{\S} in regexp | |
600 | matches any character whose syntax is not @var{code}. | |
a8b5bbef DL |
601 | |
602 | @item \c@var{c} | |
603 | matches any character whose category is @var{c}. Here @var{c} is a | |
604 | character that represents a category: thus, @samp{c} for Chinese | |
605 | characters or @samp{g} for Greek characters in the standard category | |
606 | table. | |
607 | ||
608 | @item \C@var{c} | |
609 | matches any character whose category is not @var{c}. | |
7015aca4 RS |
610 | @end table |
611 | ||
61cfa852 | 612 | The following regular expression constructs match the empty string---that is, |
7015aca4 RS |
613 | they don't use up any characters---but whether they match depends on the |
614 | context. | |
615 | ||
969fe9b5 | 616 | @table @samp |
7015aca4 RS |
617 | @item \` |
618 | @cindex @samp{\`} in regexp | |
619 | matches the empty string, but only at the beginning | |
620 | of the buffer or string being matched against. | |
621 | ||
622 | @item \' | |
623 | @cindex @samp{\'} in regexp | |
624 | matches the empty string, but only at the end of | |
625 | the buffer or string being matched against. | |
626 | ||
627 | @item \= | |
628 | @cindex @samp{\=} in regexp | |
629 | matches the empty string, but only at point. | |
630 | (This construct is not defined when matching against a string.) | |
631 | ||
632 | @item \b | |
633 | @cindex @samp{\b} in regexp | |
634 | matches the empty string, but only at the beginning or | |
635 | end of a word. Thus, @samp{\bfoo\b} matches any occurrence of | |
636 | @samp{foo} as a separate word. @samp{\bballs?\b} matches | |
637 | @samp{ball} or @samp{balls} as a separate word.@refill | |
638 | ||
1cd71ce0 RS |
639 | @samp{\b} matches at the beginning or end of the buffer |
640 | regardless of what text appears next to it. | |
641 | ||
7015aca4 RS |
642 | @item \B |
643 | @cindex @samp{\B} in regexp | |
644 | matches the empty string, but @emph{not} at the beginning or | |
645 | end of a word. | |
646 | ||
647 | @item \< | |
648 | @cindex @samp{\<} in regexp | |
649 | matches the empty string, but only at the beginning of a word. | |
1cd71ce0 RS |
650 | @samp{\<} matches at the beginning of the buffer only if a |
651 | word-constituent character follows. | |
7015aca4 RS |
652 | |
653 | @item \> | |
654 | @cindex @samp{\>} in regexp | |
1cd71ce0 RS |
655 | matches the empty string, but only at the end of a word. @samp{\>} |
656 | matches at the end of the buffer only if the contents end with a | |
657 | word-constituent character. | |
7015aca4 RS |
658 | @end table |
659 | ||
660 | @kindex invalid-regexp | |
661 | Not every string is a valid regular expression. For example, a string | |
662 | with unbalanced square brackets is invalid (with a few exceptions, such | |
61cfa852 | 663 | as @samp{[]]}), and so is a string that ends with a single @samp{\}. If |
7015aca4 RS |
664 | an invalid regular expression is passed to any of the search functions, |
665 | an @code{invalid-regexp} error is signaled. | |
666 | ||
7015aca4 RS |
667 | @node Regexp Example |
668 | @comment node-name, next, previous, up | |
669 | @subsection Complex Regexp Example | |
670 | ||
671 | Here is a complicated regexp, used by Emacs to recognize the end of a | |
672 | sentence together with any whitespace that follows. It is the value of | |
177c0ea7 | 673 | the variable @code{sentence-end}. |
7015aca4 RS |
674 | |
675 | First, we show the regexp as a string in Lisp syntax to distinguish | |
676 | spaces from tab characters. The string constant begins and ends with a | |
677 | double-quote. @samp{\"} stands for a double-quote as part of the | |
678 | string, @samp{\\} for a backslash as part of the string, @samp{\t} for a | |
679 | tab and @samp{\n} for a newline. | |
680 | ||
681 | @example | |
682 | "[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*" | |
683 | @end example | |
684 | ||
969fe9b5 RS |
685 | @noindent |
686 | In contrast, if you evaluate the variable @code{sentence-end}, you | |
7015aca4 RS |
687 | will see the following: |
688 | ||
689 | @example | |
690 | @group | |
691 | sentence-end | |
177c0ea7 | 692 | @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[ |
7015aca4 RS |
693 | ]*" |
694 | @end group | |
695 | @end example | |
696 | ||
697 | @noindent | |
698 | In this output, tab and newline appear as themselves. | |
699 | ||
700 | This regular expression contains four parts in succession and can be | |
701 | deciphered as follows: | |
702 | ||
703 | @table @code | |
704 | @item [.?!] | |
969fe9b5 RS |
705 | The first part of the pattern is a character alternative that matches |
706 | any one of three characters: period, question mark, and exclamation | |
707 | mark. The match must begin with one of these three characters. | |
7015aca4 RS |
708 | |
709 | @item []\"')@}]* | |
710 | The second part of the pattern matches any closing braces and quotation | |
711 | marks, zero or more of them, that may follow the period, question mark | |
712 | or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in | |
713 | a string. The @samp{*} at the end indicates that the immediately | |
969fe9b5 | 714 | preceding regular expression (a character alternative, in this case) may be |
7015aca4 RS |
715 | repeated zero or more times. |
716 | ||
7fd1911a | 717 | @item \\($\\|@ $\\|\t\\|@ @ \\) |
7015aca4 | 718 | The third part of the pattern matches the whitespace that follows the |
f9f59935 RS |
719 | end of a sentence: the end of a line (optionally with a space), or a |
720 | tab, or two spaces. The double backslashes mark the parentheses and | |
721 | vertical bars as regular expression syntax; the parentheses delimit a | |
722 | group and the vertical bars separate alternatives. The dollar sign is | |
723 | used to match the end of a line. | |
7015aca4 RS |
724 | |
725 | @item [ \t\n]* | |
726 | Finally, the last part of the pattern matches any additional whitespace | |
727 | beyond the minimum needed to end a sentence. | |
728 | @end table | |
729 | ||
8241495d RS |
730 | @node Regexp Functions |
731 | @subsection Regular Expression Functions | |
732 | ||
733 | These functions operate on regular expressions. | |
734 | ||
735 | @defun regexp-quote string | |
736 | This function returns a regular expression whose only exact match is | |
737 | @var{string}. Using this regular expression in @code{looking-at} will | |
738 | succeed only if the next characters in the buffer are @var{string}; | |
739 | using it in a search function will succeed if the text being searched | |
740 | contains @var{string}. | |
741 | ||
742 | This allows you to request an exact string match or search when calling | |
743 | a function that wants a regular expression. | |
744 | ||
745 | @example | |
746 | @group | |
747 | (regexp-quote "^The cat$") | |
748 | @result{} "\\^The cat\\$" | |
749 | @end group | |
750 | @end example | |
751 | ||
752 | One use of @code{regexp-quote} is to combine an exact string match with | |
753 | context described as a regular expression. For example, this searches | |
754 | for the string that is the value of @var{string}, surrounded by | |
755 | whitespace: | |
756 | ||
757 | @example | |
758 | @group | |
759 | (re-search-forward | |
760 | (concat "\\s-" (regexp-quote string) "\\s-")) | |
761 | @end group | |
762 | @end example | |
763 | @end defun | |
764 | ||
765 | @defun regexp-opt strings &optional paren | |
8241495d RS |
766 | This function returns an efficient regular expression that will match |
767 | any of the strings @var{strings}. This is useful when you need to make | |
768 | matching or searching as fast as possible---for example, for Font Lock | |
769 | mode. | |
770 | ||
771 | If the optional argument @var{paren} is non-@code{nil}, then the | |
772 | returned regular expression is always enclosed by at least one | |
773 | parentheses-grouping construct. | |
774 | ||
775 | This simplified definition of @code{regexp-opt} produces a | |
776 | regular expression which is equivalent to the actual value | |
777 | (but not as efficient): | |
778 | ||
779 | @example | |
780 | (defun regexp-opt (strings paren) | |
781 | (let ((open-paren (if paren "\\(" "")) | |
782 | (close-paren (if paren "\\)" ""))) | |
783 | (concat open-paren | |
784 | (mapconcat 'regexp-quote strings "\\|") | |
785 | close-paren))) | |
786 | @end example | |
787 | @end defun | |
788 | ||
789 | @defun regexp-opt-depth regexp | |
8241495d RS |
790 | This function returns the total number of grouping constructs |
791 | (parenthesized expressions) in @var{regexp}. | |
792 | @end defun | |
793 | ||
7015aca4 RS |
794 | @node Regexp Search |
795 | @section Regular Expression Searching | |
796 | @cindex regular expression searching | |
797 | @cindex regexp searching | |
798 | @cindex searching for regexp | |
799 | ||
969fe9b5 RS |
800 | In GNU Emacs, you can search for the next match for a regular |
801 | expression either incrementally or not. For incremental search | |
802 | commands, see @ref{Regexp Search, , Regular Expression Search, emacs, | |
803 | The GNU Emacs Manual}. Here we describe only the search functions | |
804 | useful in programs. The principal one is @code{re-search-forward}. | |
7015aca4 | 805 | |
f9f59935 RS |
806 | These search functions convert the regular expression to multibyte if |
807 | the buffer is multibyte; they convert the regular expression to unibyte | |
808 | if the buffer is unibyte. @xref{Text Representations}. | |
809 | ||
7015aca4 RS |
810 | @deffn Command re-search-forward regexp &optional limit noerror repeat |
811 | This function searches forward in the current buffer for a string of | |
812 | text that is matched by the regular expression @var{regexp}. The | |
813 | function skips over any amount of text that is not matched by | |
814 | @var{regexp}, and leaves point at the end of the first match found. | |
815 | It returns the new value of point. | |
816 | ||
817 | If @var{limit} is non-@code{nil} (it must be a position in the current | |
818 | buffer), then it is the upper bound to the search. No match extending | |
819 | after that position is accepted. | |
820 | ||
f9f59935 RS |
821 | If @var{repeat} is supplied (it must be a positive number), then the |
822 | search is repeated that many times (each time starting at the end of the | |
823 | previous time's match). If all these successive searches succeed, the | |
824 | function succeeds, moving point and returning its new value. Otherwise | |
825 | the function fails. | |
826 | ||
827 | What happens when the function fails depends on the value of | |
7015aca4 RS |
828 | @var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed} |
829 | error is signaled. If @var{noerror} is @code{t}, | |
830 | @code{re-search-forward} does nothing and returns @code{nil}. If | |
831 | @var{noerror} is neither @code{nil} nor @code{t}, then | |
832 | @code{re-search-forward} moves point to @var{limit} (or the end of the | |
833 | buffer) and returns @code{nil}. | |
834 | ||
7015aca4 RS |
835 | In the following example, point is initially before the @samp{T}. |
836 | Evaluating the search call moves point to the end of that line (between | |
837 | the @samp{t} of @samp{hat} and the newline). | |
838 | ||
839 | @example | |
840 | @group | |
841 | ---------- Buffer: foo ---------- | |
842 | I read "@point{}The cat in the hat | |
843 | comes back" twice. | |
844 | ---------- Buffer: foo ---------- | |
845 | @end group | |
846 | ||
847 | @group | |
848 | (re-search-forward "[a-z]+" nil t 5) | |
849 | @result{} 27 | |
850 | ||
851 | ---------- Buffer: foo ---------- | |
852 | I read "The cat in the hat@point{} | |
853 | comes back" twice. | |
854 | ---------- Buffer: foo ---------- | |
855 | @end group | |
856 | @end example | |
857 | @end deffn | |
858 | ||
859 | @deffn Command re-search-backward regexp &optional limit noerror repeat | |
860 | This function searches backward in the current buffer for a string of | |
861 | text that is matched by the regular expression @var{regexp}, leaving | |
862 | point at the beginning of the first text found. | |
863 | ||
7fd1911a RS |
864 | This function is analogous to @code{re-search-forward}, but they are not |
865 | simple mirror images. @code{re-search-forward} finds the match whose | |
866 | beginning is as close as possible to the starting point. If | |
867 | @code{re-search-backward} were a perfect mirror image, it would find the | |
868 | match whose end is as close as possible. However, in fact it finds the | |
3f63de1e | 869 | match whose beginning is as close as possible. The reason for this is that |
7fd1911a RS |
870 | matching a regular expression at a given spot always works from |
871 | beginning to end, and starts at a specified beginning position. | |
7015aca4 RS |
872 | |
873 | A true mirror-image of @code{re-search-forward} would require a special | |
969fe9b5 RS |
874 | feature for matching regular expressions from end to beginning. It's |
875 | not worth the trouble of implementing that. | |
7015aca4 RS |
876 | @end deffn |
877 | ||
878 | @defun string-match regexp string &optional start | |
879 | This function returns the index of the start of the first match for | |
880 | the regular expression @var{regexp} in @var{string}, or @code{nil} if | |
881 | there is no match. If @var{start} is non-@code{nil}, the search starts | |
882 | at that index in @var{string}. | |
883 | ||
884 | For example, | |
885 | ||
886 | @example | |
887 | @group | |
888 | (string-match | |
889 | "quick" "The quick brown fox jumped quickly.") | |
890 | @result{} 4 | |
891 | @end group | |
892 | @group | |
893 | (string-match | |
894 | "quick" "The quick brown fox jumped quickly." 8) | |
895 | @result{} 27 | |
896 | @end group | |
897 | @end example | |
898 | ||
899 | @noindent | |
900 | The index of the first character of the | |
901 | string is 0, the index of the second character is 1, and so on. | |
902 | ||
903 | After this function returns, the index of the first character beyond | |
904 | the match is available as @code{(match-end 0)}. @xref{Match Data}. | |
905 | ||
906 | @example | |
907 | @group | |
908 | (string-match | |
909 | "quick" "The quick brown fox jumped quickly." 8) | |
910 | @result{} 27 | |
911 | @end group | |
912 | ||
913 | @group | |
914 | (match-end 0) | |
915 | @result{} 32 | |
916 | @end group | |
917 | @end example | |
918 | @end defun | |
919 | ||
920 | @defun looking-at regexp | |
921 | This function determines whether the text in the current buffer directly | |
922 | following point matches the regular expression @var{regexp}. ``Directly | |
923 | following'' means precisely that: the search is ``anchored'' and it can | |
924 | succeed only starting with the first character following point. The | |
925 | result is @code{t} if so, @code{nil} otherwise. | |
926 | ||
927 | This function does not move point, but it updates the match data, which | |
928 | you can access using @code{match-beginning} and @code{match-end}. | |
929 | @xref{Match Data}. | |
930 | ||
931 | In this example, point is located directly before the @samp{T}. If it | |
932 | were anywhere else, the result would be @code{nil}. | |
933 | ||
934 | @example | |
935 | @group | |
936 | ---------- Buffer: foo ---------- | |
937 | I read "@point{}The cat in the hat | |
938 | comes back" twice. | |
939 | ---------- Buffer: foo ---------- | |
940 | ||
941 | (looking-at "The cat in the hat$") | |
942 | @result{} t | |
943 | @end group | |
944 | @end example | |
945 | @end defun | |
946 | ||
22697dac KH |
947 | @node POSIX Regexps |
948 | @section POSIX Regular Expression Searching | |
949 | ||
950 | The usual regular expression functions do backtracking when necessary | |
951 | to handle the @samp{\|} and repetition constructs, but they continue | |
952 | this only until they find @emph{some} match. Then they succeed and | |
953 | report the first match found. | |
954 | ||
955 | This section describes alternative search functions which perform the | |
956 | full backtracking specified by the POSIX standard for regular expression | |
957 | matching. They continue backtracking until they have tried all | |
958 | possibilities and found all matches, so they can report the longest | |
959 | match, as required by POSIX. This is much slower, so use these | |
960 | functions only when you really need the longest match. | |
961 | ||
01913af2 RS |
962 | The POSIX search and match functions do not properly support the |
963 | non-greedy repetition operators. This is because POSIX backtracking | |
964 | conflicts with the semantics of non-greedy repetition. | |
965 | ||
22697dac KH |
966 | @defun posix-search-forward regexp &optional limit noerror repeat |
967 | This is like @code{re-search-forward} except that it performs the full | |
968 | backtracking specified by the POSIX standard for regular expression | |
969 | matching. | |
970 | @end defun | |
971 | ||
972 | @defun posix-search-backward regexp &optional limit noerror repeat | |
973 | This is like @code{re-search-backward} except that it performs the full | |
974 | backtracking specified by the POSIX standard for regular expression | |
975 | matching. | |
976 | @end defun | |
977 | ||
978 | @defun posix-looking-at regexp | |
979 | This is like @code{looking-at} except that it performs the full | |
980 | backtracking specified by the POSIX standard for regular expression | |
981 | matching. | |
982 | @end defun | |
983 | ||
984 | @defun posix-string-match regexp string &optional start | |
985 | This is like @code{string-match} except that it performs the full | |
986 | backtracking specified by the POSIX standard for regular expression | |
987 | matching. | |
988 | @end defun | |
989 | ||
7015aca4 RS |
990 | @ignore |
991 | @deffn Command delete-matching-lines regexp | |
992 | This function is identical to @code{delete-non-matching-lines}, save | |
993 | that it deletes what @code{delete-non-matching-lines} keeps. | |
994 | ||
995 | In the example below, point is located on the first line of text. | |
996 | ||
997 | @example | |
998 | @group | |
999 | ---------- Buffer: foo ---------- | |
1000 | We hold these truths | |
1001 | to be self-evident, | |
1002 | that all men are created | |
1003 | equal, and that they are | |
1004 | ---------- Buffer: foo ---------- | |
1005 | @end group | |
1006 | ||
1007 | @group | |
1008 | (delete-matching-lines "the") | |
1009 | @result{} nil | |
1010 | ||
1011 | ---------- Buffer: foo ---------- | |
1012 | to be self-evident, | |
1013 | that all men are created | |
1014 | ---------- Buffer: foo ---------- | |
1015 | @end group | |
1016 | @end example | |
1017 | @end deffn | |
1018 | ||
1019 | @deffn Command flush-lines regexp | |
1020 | This function is the same as @code{delete-matching-lines}. | |
1021 | @end deffn | |
1022 | ||
1023 | @defun delete-non-matching-lines regexp | |
1024 | This function deletes all lines following point which don't | |
1025 | contain a match for the regular expression @var{regexp}. | |
1026 | @end defun | |
1027 | ||
1028 | @deffn Command keep-lines regexp | |
1029 | This function is the same as @code{delete-non-matching-lines}. | |
1030 | @end deffn | |
1031 | ||
1032 | @deffn Command how-many regexp | |
1033 | This function counts the number of matches for @var{regexp} there are in | |
1034 | the current buffer following point. It prints this number in | |
1035 | the echo area, returning the string printed. | |
1036 | @end deffn | |
1037 | ||
1038 | @deffn Command count-matches regexp | |
1039 | This function is a synonym of @code{how-many}. | |
1040 | @end deffn | |
1041 | ||
79ddc9c9 | 1042 | @deffn Command list-matching-lines regexp &optional nlines |
7015aca4 RS |
1043 | This function is a synonym of @code{occur}. |
1044 | Show all lines following point containing a match for @var{regexp}. | |
1045 | Display each line with @var{nlines} lines before and after, | |
1046 | or @code{-}@var{nlines} before if @var{nlines} is negative. | |
1047 | @var{nlines} defaults to @code{list-matching-lines-default-context-lines}. | |
1048 | Interactively it is the prefix arg. | |
1049 | ||
1050 | The lines are shown in a buffer named @samp{*Occur*}. | |
1051 | It serves as a menu to find any of the occurrences in this buffer. | |
86494bd5 | 1052 | @kbd{C-h m} (@code{describe-mode}) in that buffer gives help. |
7015aca4 RS |
1053 | @end deffn |
1054 | ||
1055 | @defopt list-matching-lines-default-context-lines | |
1056 | Default value is 0. | |
1057 | Default number of context lines to include around a @code{list-matching-lines} | |
1058 | match. A negative number means to include that many lines before the match. | |
1059 | A positive number means to include that many lines both before and after. | |
1060 | @end defopt | |
1061 | @end ignore | |
1062 | ||
1063 | @node Search and Replace | |
1064 | @section Search and Replace | |
1065 | @cindex replacement | |
1066 | ||
09facbd2 | 1067 | @defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map start end |
3da17c12 GM |
1068 | This function is the guts of @code{query-replace} and related |
1069 | commands. It searches for occurrences of @var{from-string} in the | |
1070 | text between positions @var{start} and @var{end} and replaces some or | |
09facbd2 RS |
1071 | all of them. If @var{start} is @code{nil} (or omitted), point is used |
1072 | instead, and the buffer's end is used for @var{end}. | |
3da17c12 GM |
1073 | |
1074 | If @var{query-flag} is @code{nil}, it replaces all | |
7015aca4 RS |
1075 | occurrences; otherwise, it asks the user what to do about each one. |
1076 | ||
1077 | If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is | |
1078 | considered a regular expression; otherwise, it must match literally. If | |
1079 | @var{delimited-flag} is non-@code{nil}, then only replacements | |
1080 | surrounded by word boundaries are considered. | |
1081 | ||
1082 | The argument @var{replacements} specifies what to replace occurrences | |
1083 | with. If it is a string, that string is used. It can also be a list of | |
1084 | strings, to be used in cyclic order. | |
1085 | ||
13ede7fc | 1086 | If @var{replacements} is a cons cell, @code{(@var{function} |
8241495d RS |
1087 | . @var{data})}, this means to call @var{function} after each match to |
1088 | get the replacement text. This function is called with two arguments: | |
1089 | @var{data}, and the number of replacements already made. | |
1090 | ||
bda144f4 MW |
1091 | If @var{repeat-count} is non-@code{nil}, it should be an integer. Then |
1092 | it specifies how many times to use each of the strings in the | |
1093 | @var{replacements} list before advancing cyclicly to the next one. | |
7015aca4 | 1094 | |
8241495d RS |
1095 | If @var{from-string} contains upper-case letters, then |
1096 | @code{perform-replace} binds @code{case-fold-search} to @code{nil}, and | |
1097 | it uses the @code{replacements} without altering the case of them. | |
1098 | ||
7015aca4 | 1099 | Normally, the keymap @code{query-replace-map} defines the possible user |
7fd1911a RS |
1100 | responses for queries. The argument @var{map}, if non-@code{nil}, is a |
1101 | keymap to use instead of @code{query-replace-map}. | |
7015aca4 RS |
1102 | @end defun |
1103 | ||
1104 | @defvar query-replace-map | |
1105 | This variable holds a special keymap that defines the valid user | |
1106 | responses for @code{query-replace} and related functions, as well as | |
1107 | @code{y-or-n-p} and @code{map-y-or-n-p}. It is unusual in two ways: | |
1108 | ||
1109 | @itemize @bullet | |
1110 | @item | |
1111 | The ``key bindings'' are not commands, just symbols that are meaningful | |
1112 | to the functions that use this map. | |
1113 | ||
1114 | @item | |
f9f59935 RS |
1115 | Prefix keys are not supported; each key binding must be for a |
1116 | single-event key sequence. This is because the functions don't use | |
1117 | @code{read-key-sequence} to get the input; instead, they read a single | |
1118 | event and look it up ``by hand.'' | |
7015aca4 RS |
1119 | @end itemize |
1120 | @end defvar | |
1121 | ||
1122 | Here are the meaningful ``bindings'' for @code{query-replace-map}. | |
1123 | Several of them are meaningful only for @code{query-replace} and | |
1124 | friends. | |
1125 | ||
1126 | @table @code | |
1127 | @item act | |
1128 | Do take the action being considered---in other words, ``yes.'' | |
1129 | ||
1130 | @item skip | |
1131 | Do not take action for this question---in other words, ``no.'' | |
1132 | ||
1133 | @item exit | |
7fd1911a RS |
1134 | Answer this question ``no,'' and give up on the entire series of |
1135 | questions, assuming that the answers will be ``no.'' | |
7015aca4 RS |
1136 | |
1137 | @item act-and-exit | |
7fd1911a RS |
1138 | Answer this question ``yes,'' and give up on the entire series of |
1139 | questions, assuming that subsequent answers will be ``no.'' | |
7015aca4 RS |
1140 | |
1141 | @item act-and-show | |
1142 | Answer this question ``yes,'' but show the results---don't advance yet | |
1143 | to the next question. | |
1144 | ||
1145 | @item automatic | |
1146 | Answer this question and all subsequent questions in the series with | |
1147 | ``yes,'' without further user interaction. | |
1148 | ||
1149 | @item backup | |
1150 | Move back to the previous place that a question was asked about. | |
1151 | ||
1152 | @item edit | |
1153 | Enter a recursive edit to deal with this question---instead of any | |
1154 | other action that would normally be taken. | |
1155 | ||
1156 | @item delete-and-edit | |
1157 | Delete the text being considered, then enter a recursive edit to replace | |
1158 | it. | |
1159 | ||
1160 | @item recenter | |
1161 | Redisplay and center the window, then ask the same question again. | |
1162 | ||
1163 | @item quit | |
1164 | Perform a quit right away. Only @code{y-or-n-p} and related functions | |
1165 | use this answer. | |
1166 | ||
1167 | @item help | |
1168 | Display some help, then ask again. | |
1169 | @end table | |
1170 | ||
1171 | @node Match Data | |
1172 | @section The Match Data | |
1173 | @cindex match data | |
1174 | ||
3f63de1e | 1175 | Emacs keeps track of the start and end positions of the segments of |
7015aca4 RS |
1176 | text found during a regular expression search. This means, for example, |
1177 | that you can search for a complex pattern, such as a date in an Rmail | |
1178 | message, and then extract parts of the match under control of the | |
1179 | pattern. | |
1180 | ||
1181 | Because the match data normally describe the most recent search only, | |
1182 | you must be careful not to do another search inadvertently between the | |
1183 | search you wish to refer back to and the use of the match data. If you | |
1184 | can't avoid another intervening search, you must save and restore the | |
1185 | match data around it, to prevent it from being overwritten. | |
1186 | ||
1187 | @menu | |
969fe9b5 | 1188 | * Replacing Match:: Replacing a substring that was matched. |
7015aca4 RS |
1189 | * Simple Match Data:: Accessing single items of match data, |
1190 | such as where a particular subexpression started. | |
7015aca4 RS |
1191 | * Entire Match Data:: Accessing the entire match data at once, as a list. |
1192 | * Saving Match Data:: Saving and restoring the match data. | |
1193 | @end menu | |
1194 | ||
969fe9b5 | 1195 | @node Replacing Match |
8241495d | 1196 | @subsection Replacing the Text that Matched |
969fe9b5 RS |
1197 | |
1198 | This function replaces the text matched by the last search with | |
1199 | @var{replacement}. | |
1200 | ||
1201 | @cindex case in replacements | |
1202 | @defun replace-match replacement &optional fixedcase literal string subexp | |
1203 | This function replaces the text in the buffer (or in @var{string}) that | |
1204 | was matched by the last search. It replaces that text with | |
1205 | @var{replacement}. | |
1206 | ||
1207 | If you did the last search in a buffer, you should specify @code{nil} | |
1208 | for @var{string}. Then @code{replace-match} does the replacement by | |
1209 | editing the buffer; it leaves point at the end of the replacement text, | |
1210 | and returns @code{t}. | |
1211 | ||
1212 | If you did the search in a string, pass the same string as @var{string}. | |
1213 | Then @code{replace-match} does the replacement by constructing and | |
1214 | returning a new string. | |
1215 | ||
2037b263 RS |
1216 | If @var{fixedcase} is non-@code{nil}, then @code{replace-match} uses |
1217 | the replacement text without case conversion; otherwise, it converts | |
1218 | the replacement text depending upon the capitalization of the text to | |
1219 | be replaced. If the original text is all upper case, this converts | |
1220 | the replacement text to upper case. If all words of the original text | |
1221 | are capitalized, this capitalizes all the words of the replacement | |
1222 | text. If all the words are one-letter and they are all upper case, | |
1223 | they are treated as capitalized words rather than all-upper-case | |
1224 | words. | |
969fe9b5 | 1225 | |
969fe9b5 RS |
1226 | If @var{literal} is non-@code{nil}, then @var{replacement} is inserted |
1227 | exactly as it is, the only alterations being case changes as needed. | |
1228 | If it is @code{nil} (the default), then the character @samp{\} is treated | |
1229 | specially. If a @samp{\} appears in @var{replacement}, then it must be | |
1230 | part of one of the following sequences: | |
1231 | ||
1232 | @table @asis | |
1233 | @item @samp{\&} | |
1234 | @cindex @samp{&} in replacement | |
1235 | @samp{\&} stands for the entire text being replaced. | |
1236 | ||
1237 | @item @samp{\@var{n}} | |
1238 | @cindex @samp{\@var{n}} in replacement | |
1239 | @samp{\@var{n}}, where @var{n} is a digit, stands for the text that | |
1240 | matched the @var{n}th subexpression in the original regexp. | |
1241 | Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}. | |
1242 | ||
1243 | @item @samp{\\} | |
1244 | @cindex @samp{\} in replacement | |
1245 | @samp{\\} stands for a single @samp{\} in the replacement text. | |
1246 | @end table | |
1247 | ||
2037b263 RS |
1248 | These substitutions occur after case conversion, if any, |
1249 | so the strings they substitute are never case-converted. | |
1250 | ||
969fe9b5 RS |
1251 | If @var{subexp} is non-@code{nil}, that says to replace just |
1252 | subexpression number @var{subexp} of the regexp that was matched, not | |
1253 | the entire match. For example, after matching @samp{foo \(ba*r\)}, | |
1254 | calling @code{replace-match} with 1 as @var{subexp} means to replace | |
1255 | just the text that matched @samp{\(ba*r\)}. | |
1256 | @end defun | |
1257 | ||
7015aca4 RS |
1258 | @node Simple Match Data |
1259 | @subsection Simple Match Data Access | |
1260 | ||
22697dac | 1261 | This section explains how to use the match data to find out what was |
87bf725e | 1262 | matched by the last search or match operation, if it succeeded. |
22697dac KH |
1263 | |
1264 | You can ask about the entire matching text, or about a particular | |
1265 | parenthetical subexpression of a regular expression. The @var{count} | |
1266 | argument in the functions below specifies which. If @var{count} is | |
1267 | zero, you are asking about the entire match. If @var{count} is | |
1268 | positive, it specifies which subexpression you want. | |
1269 | ||
1270 | Recall that the subexpressions of a regular expression are those | |
1271 | expressions grouped with escaped parentheses, @samp{\(@dots{}\)}. The | |
1272 | @var{count}th subexpression is found by counting occurrences of | |
1273 | @samp{\(} from the beginning of the whole regular expression. The first | |
1274 | subexpression is numbered 1, the second 2, and so on. Only regular | |
1275 | expressions can have subexpressions---after a simple string search, the | |
1276 | only information available is about the entire match. | |
1277 | ||
a9f0a989 RS |
1278 | A search which fails may or may not alter the match data. In the |
1279 | past, a failing search did not do this, but we may change it in the | |
87bf725e RS |
1280 | future. So don't try to rely on the value of the match data after |
1281 | a failing search. | |
a9f0a989 | 1282 | |
22697dac KH |
1283 | @defun match-string count &optional in-string |
1284 | This function returns, as a string, the text matched in the last search | |
1285 | or match operation. It returns the entire text if @var{count} is zero, | |
1286 | or just the portion corresponding to the @var{count}th parenthetical | |
a5d0a32e | 1287 | subexpression, if @var{count} is positive. |
22697dac KH |
1288 | |
1289 | If the last such operation was done against a string with | |
1290 | @code{string-match}, then you should pass the same string as the | |
969fe9b5 | 1291 | argument @var{in-string}. After a buffer search or match, |
22697dac KH |
1292 | you should omit @var{in-string} or pass @code{nil} for it; but you |
1293 | should make sure that the current buffer when you call | |
1294 | @code{match-string} is the one in which you did the searching or | |
1295 | matching. | |
a5d0a32e RS |
1296 | |
1297 | The value is @code{nil} if @var{count} is out of range, or for a | |
1298 | subexpression inside a @samp{\|} alternative that wasn't used or a | |
1299 | repetition that repeated zero times. | |
22697dac | 1300 | @end defun |
7015aca4 | 1301 | |
79ddc9c9 | 1302 | @defun match-string-no-properties count &optional in-string |
f9f59935 RS |
1303 | This function is like @code{match-string} except that the result |
1304 | has no text properties. | |
1305 | @end defun | |
1306 | ||
7015aca4 RS |
1307 | @defun match-beginning count |
1308 | This function returns the position of the start of text matched by the | |
1309 | last regular expression searched for, or a subexpression of it. | |
1310 | ||
7fd1911a | 1311 | If @var{count} is zero, then the value is the position of the start of |
eaac2be1 | 1312 | the entire match. Otherwise, @var{count} specifies a subexpression in |
969fe9b5 | 1313 | the regular expression, and the value of the function is the starting |
22697dac KH |
1314 | position of the match for that subexpression. |
1315 | ||
1316 | The value is @code{nil} for a subexpression inside a @samp{\|} | |
a5d0a32e | 1317 | alternative that wasn't used or a repetition that repeated zero times. |
7015aca4 RS |
1318 | @end defun |
1319 | ||
1320 | @defun match-end count | |
22697dac KH |
1321 | This function is like @code{match-beginning} except that it returns the |
1322 | position of the end of the match, rather than the position of the | |
1323 | beginning. | |
7015aca4 RS |
1324 | @end defun |
1325 | ||
1326 | Here is an example of using the match data, with a comment showing the | |
1327 | positions within the text: | |
1328 | ||
1329 | @example | |
1330 | @group | |
1331 | (string-match "\\(qu\\)\\(ick\\)" | |
1332 | "The quick fox jumped quickly.") | |
177c0ea7 | 1333 | ;0123456789 |
7015aca4 RS |
1334 | @result{} 4 |
1335 | @end group | |
1336 | ||
22697dac KH |
1337 | @group |
1338 | (match-string 0 "The quick fox jumped quickly.") | |
1339 | @result{} "quick" | |
1340 | (match-string 1 "The quick fox jumped quickly.") | |
1341 | @result{} "qu" | |
1342 | (match-string 2 "The quick fox jumped quickly.") | |
1343 | @result{} "ick" | |
1344 | @end group | |
1345 | ||
7015aca4 RS |
1346 | @group |
1347 | (match-beginning 1) ; @r{The beginning of the match} | |
1348 | @result{} 4 ; @r{with @samp{qu} is at index 4.} | |
1349 | @end group | |
1350 | ||
1351 | @group | |
1352 | (match-beginning 2) ; @r{The beginning of the match} | |
1353 | @result{} 6 ; @r{with @samp{ick} is at index 6.} | |
1354 | @end group | |
1355 | ||
1356 | @group | |
1357 | (match-end 1) ; @r{The end of the match} | |
1358 | @result{} 6 ; @r{with @samp{qu} is at index 6.} | |
1359 | ||
1360 | (match-end 2) ; @r{The end of the match} | |
1361 | @result{} 9 ; @r{with @samp{ick} is at index 9.} | |
1362 | @end group | |
1363 | @end example | |
1364 | ||
1365 | Here is another example. Point is initially located at the beginning | |
1366 | of the line. Searching moves point to between the space and the word | |
1367 | @samp{in}. The beginning of the entire match is at the 9th character of | |
1368 | the buffer (@samp{T}), and the beginning of the match for the first | |
1369 | subexpression is at the 13th character (@samp{c}). | |
1370 | ||
1371 | @example | |
1372 | @group | |
1373 | (list | |
1374 | (re-search-forward "The \\(cat \\)") | |
1375 | (match-beginning 0) | |
1376 | (match-beginning 1)) | |
7fd1911a | 1377 | @result{} (9 9 13) |
7015aca4 RS |
1378 | @end group |
1379 | ||
1380 | @group | |
1381 | ---------- Buffer: foo ---------- | |
1382 | I read "The cat @point{}in the hat comes back" twice. | |
1383 | ^ ^ | |
1384 | 9 13 | |
1385 | ---------- Buffer: foo ---------- | |
1386 | @end group | |
1387 | @end example | |
1388 | ||
1389 | @noindent | |
1390 | (In this case, the index returned is a buffer position; the first | |
1391 | character of the buffer counts as 1.) | |
1392 | ||
7015aca4 RS |
1393 | @node Entire Match Data |
1394 | @subsection Accessing the Entire Match Data | |
1395 | ||
1396 | The functions @code{match-data} and @code{set-match-data} read or | |
1397 | write the entire match data, all at once. | |
1398 | ||
1399 | @defun match-data | |
1400 | This function returns a newly constructed list containing all the | |
1401 | information on what text the last search matched. Element zero is the | |
1402 | position of the beginning of the match for the whole expression; element | |
1403 | one is the position of the end of the match for the expression. The | |
1404 | next two elements are the positions of the beginning and end of the | |
1405 | match for the first subexpression, and so on. In general, element | |
37680279 | 1406 | @ifnottex |
7015aca4 | 1407 | number 2@var{n} |
37680279 | 1408 | @end ifnottex |
7015aca4 RS |
1409 | @tex |
1410 | number {\mathsurround=0pt $2n$} | |
1411 | @end tex | |
1412 | corresponds to @code{(match-beginning @var{n})}; and | |
1413 | element | |
37680279 | 1414 | @ifnottex |
7015aca4 | 1415 | number 2@var{n} + 1 |
37680279 | 1416 | @end ifnottex |
7015aca4 RS |
1417 | @tex |
1418 | number {\mathsurround=0pt $2n+1$} | |
1419 | @end tex | |
1420 | corresponds to @code{(match-end @var{n})}. | |
1421 | ||
1422 | All the elements are markers or @code{nil} if matching was done on a | |
1423 | buffer, and all are integers or @code{nil} if matching was done on a | |
969fe9b5 | 1424 | string with @code{string-match}. |
7015aca4 RS |
1425 | |
1426 | As always, there must be no possibility of intervening searches between | |
1427 | the call to a search function and the call to @code{match-data} that is | |
1428 | intended to access the match data for that search. | |
1429 | ||
1430 | @example | |
1431 | @group | |
1432 | (match-data) | |
1433 | @result{} (#<marker at 9 in foo> | |
1434 | #<marker at 17 in foo> | |
1435 | #<marker at 13 in foo> | |
1436 | #<marker at 17 in foo>) | |
1437 | @end group | |
1438 | @end example | |
1439 | @end defun | |
1440 | ||
1441 | @defun set-match-data match-list | |
1442 | This function sets the match data from the elements of @var{match-list}, | |
1443 | which should be a list that was the value of a previous call to | |
3ab8acb9 RS |
1444 | @code{match-data}. (More precisely, anything that has the same format |
1445 | will work.) | |
7015aca4 RS |
1446 | |
1447 | If @var{match-list} refers to a buffer that doesn't exist, you don't get | |
1448 | an error; that sets the match data in a meaningless but harmless way. | |
1449 | ||
1450 | @findex store-match-data | |
969fe9b5 | 1451 | @code{store-match-data} is a semi-obsolete alias for @code{set-match-data}. |
7015aca4 RS |
1452 | @end defun |
1453 | ||
1454 | @node Saving Match Data | |
1455 | @subsection Saving and Restoring the Match Data | |
1456 | ||
d1280259 RS |
1457 | When you call a function that may do a search, you may need to save |
1458 | and restore the match data around that call, if you want to preserve the | |
1459 | match data from an earlier search for later use. Here is an example | |
1460 | that shows the problem that arises if you fail to save the match data: | |
7015aca4 RS |
1461 | |
1462 | @example | |
1463 | @group | |
1464 | (re-search-forward "The \\(cat \\)") | |
1465 | @result{} 48 | |
1466 | (foo) ; @r{Perhaps @code{foo} does} | |
1467 | ; @r{more searching.} | |
1468 | (match-end 0) | |
1469 | @result{} 61 ; @r{Unexpected result---not 48!} | |
1470 | @end group | |
1471 | @end example | |
1472 | ||
d1280259 | 1473 | You can save and restore the match data with @code{save-match-data}: |
7015aca4 | 1474 | |
bfe721d1 | 1475 | @defmac save-match-data body@dots{} |
1911e6e5 | 1476 | This macro executes @var{body}, saving and restoring the match |
d1280259 | 1477 | data around it. |
bfe721d1 | 1478 | @end defmac |
7015aca4 | 1479 | |
969fe9b5 RS |
1480 | You could use @code{set-match-data} together with @code{match-data} to |
1481 | imitate the effect of the special form @code{save-match-data}. Here is | |
1482 | how: | |
7015aca4 RS |
1483 | |
1484 | @example | |
1485 | @group | |
1486 | (let ((data (match-data))) | |
1487 | (unwind-protect | |
f9f59935 | 1488 | @dots{} ; @r{Ok to change the original match data.} |
7015aca4 RS |
1489 | (set-match-data data))) |
1490 | @end group | |
1491 | @end example | |
1492 | ||
d1280259 RS |
1493 | Emacs automatically saves and restores the match data when it runs |
1494 | process filter functions (@pxref{Filter Functions}) and process | |
1495 | sentinels (@pxref{Sentinels}). | |
1496 | ||
7015aca4 RS |
1497 | @ignore |
1498 | Here is a function which restores the match data provided the buffer | |
1499 | associated with it still exists. | |
1500 | ||
1501 | @smallexample | |
1502 | @group | |
1503 | (defun restore-match-data (data) | |
1504 | @c It is incorrect to split the first line of a doc string. | |
1505 | @c If there's a problem here, it should be solved in some other way. | |
1506 | "Restore the match data DATA unless the buffer is missing." | |
1507 | (catch 'foo | |
1508 | (let ((d data)) | |
1509 | @end group | |
1510 | (while d | |
1511 | (and (car d) | |
1512 | (null (marker-buffer (car d))) | |
1513 | @group | |
1514 | ;; @file{match-data} @r{buffer is deleted.} | |
1515 | (throw 'foo nil)) | |
1516 | (setq d (cdr d))) | |
1517 | (set-match-data data)))) | |
1518 | @end group | |
1519 | @end smallexample | |
1520 | @end ignore | |
1521 | ||
1522 | @node Searching and Case | |
1523 | @section Searching and Case | |
1524 | @cindex searching and case | |
1525 | ||
1526 | By default, searches in Emacs ignore the case of the text they are | |
1527 | searching through; if you specify searching for @samp{FOO}, then | |
f9f59935 RS |
1528 | @samp{Foo} or @samp{foo} is also considered a match. This applies to |
1529 | regular expressions, too; thus, @samp{[aB]} would match @samp{a} or | |
1530 | @samp{A} or @samp{b} or @samp{B}. | |
7015aca4 RS |
1531 | |
1532 | If you do not want this feature, set the variable | |
1533 | @code{case-fold-search} to @code{nil}. Then all letters must match | |
7fd1911a RS |
1534 | exactly, including case. This is a buffer-local variable; altering the |
1535 | variable affects only the current buffer. (@xref{Intro to | |
7015aca4 RS |
1536 | Buffer-Local}.) Alternatively, you may change the value of |
1537 | @code{default-case-fold-search}, which is the default value of | |
1538 | @code{case-fold-search} for buffers that do not override it. | |
1539 | ||
1540 | Note that the user-level incremental search feature handles case | |
1541 | distinctions differently. When given a lower case letter, it looks for | |
1542 | a match of either case, but when given an upper case letter, it looks | |
1543 | for an upper case letter only. But this has nothing to do with the | |
f9f59935 | 1544 | searching functions used in Lisp code. |
7015aca4 RS |
1545 | |
1546 | @defopt case-replace | |
7fd1911a RS |
1547 | This variable determines whether the replacement functions should |
1548 | preserve case. If the variable is @code{nil}, that means to use the | |
1549 | replacement text verbatim. A non-@code{nil} value means to convert the | |
1550 | case of the replacement text according to the text being replaced. | |
1551 | ||
8241495d RS |
1552 | This variable is used by passing it as an argument to the function |
1553 | @code{replace-match}. @xref{Replacing Match}. | |
7015aca4 RS |
1554 | @end defopt |
1555 | ||
1556 | @defopt case-fold-search | |
1557 | This buffer-local variable determines whether searches should ignore | |
1558 | case. If the variable is @code{nil} they do not ignore case; otherwise | |
1559 | they do ignore case. | |
1560 | @end defopt | |
1561 | ||
1562 | @defvar default-case-fold-search | |
1563 | The value of this variable is the default value for | |
1564 | @code{case-fold-search} in buffers that do not override it. This is the | |
1565 | same as @code{(default-value 'case-fold-search)}. | |
1566 | @end defvar | |
1567 | ||
1568 | @node Standard Regexps | |
1569 | @section Standard Regular Expressions Used in Editing | |
1570 | @cindex regexps used standardly in editing | |
1571 | @cindex standard regexps used in editing | |
1572 | ||
1573 | This section describes some variables that hold regular expressions | |
1574 | used for certain purposes in editing: | |
1575 | ||
1576 | @defvar page-delimiter | |
969fe9b5 RS |
1577 | This is the regular expression describing line-beginnings that separate |
1578 | pages. The default value is @code{"^\014"} (i.e., @code{"^^L"} or | |
1579 | @code{"^\C-l"}); this matches a line that starts with a formfeed | |
1580 | character. | |
7015aca4 RS |
1581 | @end defvar |
1582 | ||
22697dac KH |
1583 | The following two regular expressions should @emph{not} assume the |
1584 | match always starts at the beginning of a line; they should not use | |
1585 | @samp{^} to anchor the match. Most often, the paragraph commands do | |
1586 | check for a match only at the beginning of a line, which means that | |
bfe721d1 KH |
1587 | @samp{^} would be superfluous. When there is a nonzero left margin, |
1588 | they accept matches that start after the left margin. In that case, a | |
1589 | @samp{^} would be incorrect. However, a @samp{^} is harmless in modes | |
1590 | where a left margin is never used. | |
22697dac | 1591 | |
7015aca4 RS |
1592 | @defvar paragraph-separate |
1593 | This is the regular expression for recognizing the beginning of a line | |
1594 | that separates paragraphs. (If you change this, you may have to | |
7fd1911a | 1595 | change @code{paragraph-start} also.) The default value is |
22697dac KH |
1596 | @w{@code{"[@ \t\f]*$"}}, which matches a line that consists entirely of |
1597 | spaces, tabs, and form feeds (after its left margin). | |
7015aca4 RS |
1598 | @end defvar |
1599 | ||
1600 | @defvar paragraph-start | |
1601 | This is the regular expression for recognizing the beginning of a line | |
1602 | that starts @emph{or} separates paragraphs. The default value is | |
22697dac KH |
1603 | @w{@code{"[@ \t\n\f]"}}, which matches a line starting with a space, tab, |
1604 | newline, or form feed (after its left margin). | |
7015aca4 RS |
1605 | @end defvar |
1606 | ||
1607 | @defvar sentence-end | |
1608 | This is the regular expression describing the end of a sentence. (All | |
1609 | paragraph boundaries also end sentences, regardless.) The default value | |
1610 | is: | |
1611 | ||
1612 | @example | |
7fd1911a | 1613 | "[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*" |
7015aca4 RS |
1614 | @end example |
1615 | ||
7fd1911a RS |
1616 | This means a period, question mark or exclamation mark, followed |
1617 | optionally by a closing parenthetical character, followed by tabs, | |
1618 | spaces or new lines. | |
7015aca4 RS |
1619 | |
1620 | For a detailed explanation of this regular expression, see @ref{Regexp | |
1621 | Example}. | |
1622 | @end defvar | |
ab5796a9 MB |
1623 | |
1624 | @ignore | |
1625 | arch-tag: c2573ca2-18aa-4839-93b8-924043ef831f | |
1626 | @end ignore |