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1 | @c This is part of the Emacs manual. |
2 | @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001, 2002, | |
6ed161e1 | 3 | @c 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
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4 | @c See file emacs.texi for copying conditions. |
5 | @node Search, Fixit, Display, Top | |
6 | @chapter Searching and Replacement | |
7 | @cindex searching | |
8 | @cindex finding strings within text | |
9 | ||
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10 | Like other editors, Emacs has commands to search for occurrences of |
11 | a string. Emacs also has commands to replace occurrences of a string | |
12 | with a different string. There are also commands that do the same | |
13 | thing, but search for patterns instead of fixed strings. | |
14 | ||
15 | You can also search multiple files under the control of a tags table | |
16 | (@pxref{Tags Search}) or through the Dired @kbd{A} command | |
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17 | (@pxref{Operating on Files}), or ask the @code{grep} program to do it |
18 | (@pxref{Grep Searching}). | |
19 | ||
20 | ||
21 | @menu | |
22 | * Incremental Search:: Search happens as you type the string. | |
23 | * Nonincremental Search:: Specify entire string and then search. | |
24 | * Word Search:: Search for sequence of words. | |
25 | * Regexp Search:: Search for match for a regexp. | |
26 | * Regexps:: Syntax of regular expressions. | |
27 | * Regexp Backslash:: Regular expression constructs starting with `\'. | |
28 | * Regexp Example:: A complex regular expression explained. | |
29 | * Search Case:: To ignore case while searching, or not. | |
30 | * Replace:: Search, and replace some or all matches. | |
31 | * Other Repeating Search:: Operating on all matches for some regexp. | |
32 | @end menu | |
33 | ||
34 | @node Incremental Search | |
35 | @section Incremental Search | |
36 | @cindex incremental search | |
37 | @cindex isearch | |
38 | ||
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39 | The principal search command in Emacs is @dfn{incremental}: it |
40 | begins searching as soon as you type the first character of the search | |
41 | string. As you type in the search string, Emacs shows you where the | |
42 | string (as you have typed it so far) would be found. When you have | |
43 | typed enough characters to identify the place you want, you can stop. | |
44 | Depending on what you plan to do next, you may or may not need to | |
45 | terminate the search explicitly with @key{RET}. | |
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46 | |
47 | @table @kbd | |
48 | @item C-s | |
49 | Incremental search forward (@code{isearch-forward}). | |
50 | @item C-r | |
51 | Incremental search backward (@code{isearch-backward}). | |
52 | @end table | |
53 | ||
54 | @menu | |
55 | * Basic Isearch:: Basic incremental search commands. | |
56 | * Repeat Isearch:: Searching for the same string again. | |
57 | * Error in Isearch:: When your string is not found. | |
58 | * Special Isearch:: Special input in incremental search. | |
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59 | * Isearch Yank:: Commands that grab text into the search string |
60 | or else edit the search string. | |
8cf51b2c | 61 | * Isearch Scroll:: Scrolling during an incremental search. |
b5fb9df5 | 62 | * Isearch Minibuffer:: Incremental search of the minibuffer history. |
8cf51b2c GM |
63 | * Slow Isearch:: Incremental search features for slow terminals. |
64 | @end menu | |
65 | ||
66 | @node Basic Isearch | |
67 | @subsection Basics of Incremental Search | |
68 | ||
b5fb9df5 | 69 | @table @kbd |
97b3a00b | 70 | @item C-s |
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71 | Begin incremental search (@code{isearch-forward}). |
72 | @item C-r | |
73 | Begin reverse incremental search (@code{isearch-backward}). | |
74 | @end table | |
75 | ||
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76 | @kindex C-s |
77 | @findex isearch-forward | |
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78 | @kbd{C-s} (@code{isearch-forward}) starts a forward incremental |
79 | search. It reads characters from the keyboard, and moves point just | |
80 | past the end of the next occurrence of those characters in the buffer. | |
81 | ||
82 | For instance, if you type @kbd{C-s} and then @kbd{F}, that puts the | |
83 | cursor after the first @samp{F} that occurs in the buffer after the | |
84 | starting point. Then if you then type @kbd{O}, the cursor moves to | |
85 | just after the first @samp{FO}; the @samp{F} in that @samp{FO} might | |
86 | not be the first @samp{F} previously found. After another @kbd{O}, | |
87 | the cursor moves to just after the first @samp{FOO}. | |
88 | ||
89 | @cindex faces for highlighting search matches | |
90 | At each step, Emacs highlights the @dfn{current match}---the buffer | |
91 | text that matches the search string---using the @code{isearch} face | |
92 | (@pxref{Faces}). The current search string is also displayed in the | |
93 | echo area. | |
94 | ||
95 | If you make a mistake typing the search string, type @key{DEL}. | |
96 | Each @key{DEL} cancels the last character of the search string. | |
97 | ||
98 | When you are satisfied with the place you have reached, type | |
99 | @key{RET}. This stops searching, leaving the cursor where the search | |
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100 | brought it. Also, any command not specially meaningful in searches |
101 | stops the searching and is then executed. Thus, typing @kbd{C-a} | |
b5fb9df5 | 102 | exits the search and then moves to the beginning of the line. |
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103 | @key{RET} is necessary only if the next command you want to type is a |
104 | printing character, @key{DEL}, @key{RET}, or another character that is | |
105 | special within searches (@kbd{C-q}, @kbd{C-w}, @kbd{C-r}, @kbd{C-s}, | |
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106 | @kbd{C-y}, @kbd{M-y}, @kbd{M-r}, @kbd{M-c}, @kbd{M-e}, and some others |
107 | described below). | |
108 | ||
109 | As a special exception, entering @key{RET} when the search string is | |
110 | empty launches nonincremental search (@pxref{Nonincremental Search}). | |
8cf51b2c | 111 | |
6184c708 | 112 | When you exit the incremental search, it adds the original value of |
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113 | point to the mark ring, without activating the mark; you can thus use |
114 | @kbd{C-u C-@key{SPC}} to return to where you were before beginning the | |
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115 | search. @xref{Mark Ring}. It only does this if the mark was not |
116 | already active. | |
8cf51b2c | 117 | |
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118 | @kindex C-r |
119 | @findex isearch-backward | |
120 | To search backwards, use @kbd{C-r} (@code{isearch-backward}) instead | |
121 | of @kbd{C-s} to start the search. A backward search finds matches | |
122 | that end before the starting point, just as a forward search finds | |
123 | matches that begin after it. | |
124 | ||
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125 | @node Repeat Isearch |
126 | @subsection Repeating Incremental Search | |
127 | ||
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128 | Suppose you search forward for @samp{FOO} and find a match, but not |
129 | the one you expected to find: the @samp{FOO} you were aiming for | |
130 | occurs later in the buffer. In this event, type another @kbd{C-s} to | |
131 | move to the next occurrence of the search string. You can repeat this | |
132 | any number of times. If you overshoot, you can cancel some @kbd{C-s} | |
133 | characters with @key{DEL}. Similarly, each @kbd{C-r} in a backward | |
134 | incremental search repeats the backward search. | |
135 | ||
136 | @cindex lazy search highlighting | |
137 | @vindex isearch-lazy-highlight | |
138 | If you pause for a little while during incremental search, Emacs | |
139 | highlights all the other possible matches for the search string that | |
140 | are present on the screen. This helps you anticipate where you can | |
141 | get to by typing @kbd{C-s} or @kbd{C-r} to repeat the search. The | |
142 | other matches are highlighted differently from the current match, | |
143 | using the customizable face @code{lazy-highlight} (@pxref{Faces}). If | |
144 | you don't like this feature, you can disable it by setting | |
145 | @code{isearch-lazy-highlight} to @code{nil}. | |
146 | ||
147 | After exiting a search, you can search for the same string again by | |
148 | typing just @kbd{C-s C-s}. The first @kbd{C-s} is the key that | |
149 | invokes incremental search, and the second @kbd{C-s} means ``search | |
150 | again.'' Similarly, @kbd{C-r C-r} searches backward for the last | |
151 | search string. In determining the last search string, it doesn't | |
152 | matter whether the string was searched for with @kbd{C-s} or | |
153 | @kbd{C-r}. | |
8cf51b2c | 154 | |
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155 | If you are searching forward but you realize you were looking for |
156 | something before the starting point, type @kbd{C-r} to switch to a | |
157 | backward search, leaving the search string unchanged. Similarly, | |
158 | @kbd{C-s} in a backward search switches to a forward search. | |
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159 | |
160 | If a search is failing and you ask to repeat it by typing another | |
161 | @kbd{C-s}, it starts again from the beginning of the buffer. | |
162 | Repeating a failing reverse search with @kbd{C-r} starts again from | |
163 | the end. This is called @dfn{wrapping around}, and @samp{Wrapped} | |
164 | appears in the search prompt once this has happened. If you keep on | |
165 | going past the original starting point of the search, it changes to | |
166 | @samp{Overwrapped}, which means that you are revisiting matches that | |
167 | you have already seen. | |
168 | ||
b5fb9df5 | 169 | @cindex search ring |
8cf51b2c | 170 | To reuse earlier search strings, use the @dfn{search ring}. The |
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171 | commands @kbd{M-p} and @kbd{M-n} move through the ring to pick a |
172 | search string to reuse. These commands leave the selected search ring | |
173 | element in the minibuffer, where you can edit it. To edit the current | |
174 | search string in the minibuffer without replacing it with items from | |
175 | the search ring, type @kbd{M-e}. Type @kbd{C-s} or @kbd{C-r} to | |
176 | terminate editing the string and search for it. | |
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177 | |
178 | @node Error in Isearch | |
179 | @subsection Errors in Incremental Search | |
180 | ||
181 | If your string is not found at all, the echo area says @samp{Failing | |
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182 | I-Search}. The cursor is after the place where Emacs found as much of |
183 | your string as it could. Thus, if you search for @samp{FOOT}, and | |
184 | there is no @samp{FOOT}, you might see the cursor after the @samp{FOO} | |
185 | in @samp{FOOL}. In the echo area, the part of the search string that | |
186 | failed to match is highlighted using the customizable face | |
187 | @code{isearch-fail}. | |
188 | ||
189 | At this point, there are several things you can do. If your string | |
190 | was mistyped, you can use @key{DEL} to erase some of it and correct | |
191 | it. If you like the place you have found, you can type @key{RET} to | |
192 | remain there. Or you can type @kbd{C-g}, which removes from the | |
193 | search string the characters that could not be found (the @samp{T} in | |
194 | @samp{FOOT}), leaving those that were found (the @samp{FOO} in | |
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195 | @samp{FOOT}). A second @kbd{C-g} at that point cancels the search |
196 | entirely, returning point to where it was when the search started. | |
197 | ||
198 | @cindex quitting (in search) | |
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199 | The quit command, @kbd{C-g}, does special things during searches; |
200 | just what it does depends on the status of the search. If the search | |
201 | has found what you specified and is waiting for input, @kbd{C-g} | |
202 | cancels the entire search, moving the cursor back to where you started | |
203 | the search. If @kbd{C-g} is typed when there are characters in the | |
204 | search string that have not been found---because Emacs is still | |
205 | searching for them, or because it has failed to find them---then the | |
206 | search string characters which have not been found are discarded from | |
207 | the search string. With them gone, the search is now successful and | |
208 | waiting for more input, so a second @kbd{C-g} will cancel the entire | |
209 | search. | |
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210 | |
211 | @node Special Isearch | |
212 | @subsection Special Input for Incremental Search | |
213 | ||
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214 | Some of the characters you type during incremental search have |
215 | special effects. | |
216 | ||
217 | If the search string you entered contains only lower-case letters, | |
218 | the search is case-insensitive; as long as an upper-case letter exists | |
219 | in the search string, the search becomes case-sensitive. If you | |
220 | delete the upper-case character from the search string, it ceases to | |
221 | have this effect. @xref{Search Case}. | |
222 | ||
223 | To search for a newline character, type @kbd{C-j}. | |
224 | ||
225 | To search for other control characters, such as @key{control-S}, | |
226 | quote it by typing @kbd{C-q} first (@pxref{Inserting Text}). To | |
227 | search for non-@acronym{ASCII} characters, you can either use | |
228 | @kbd{C-q} and enter its octal code, or use an input method | |
229 | (@pxref{Input Methods}). If an input method is enabled in the current | |
230 | buffer when you start the search, you can use it in the search string | |
231 | also. While typing the search string, you can toggle the input method | |
232 | with the command @kbd{C-\} (@code{isearch-toggle-input-method}). You | |
233 | can also turn on a non-default input method with @kbd{C-^} | |
234 | (@code{isearch-toggle-specified-input-method}), which prompts for the | |
235 | name of the input method. When an input method is active during | |
236 | incremental search, the search prompt includes the input method | |
237 | mnemonic, like this: | |
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238 | |
239 | @example | |
240 | I-search [@var{im}]: | |
241 | @end example | |
242 | ||
243 | @noindent | |
244 | @findex isearch-toggle-input-method | |
245 | @findex isearch-toggle-specified-input-method | |
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246 | where @var{im} is the mnemonic of the active input method. Any input |
247 | method you enable during incremental search remains enabled in the | |
248 | current buffer afterwards. | |
8cf51b2c | 249 | |
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250 | @kindex M-% @r{(Incremental search)} |
251 | Typing @kbd{M-%} in incremental search invokes @code{query-replace} | |
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252 | or @code{query-replace-regexp} (depending on search mode) with the |
253 | current search string used as the string to replace. @xref{Query | |
254 | Replace}. | |
255 | ||
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256 | @kindex M-TAB @r{(Incremental search)} |
257 | Typing @kbd{M-@key{TAB}} in incremental search invokes | |
258 | @code{isearch-complete}, which attempts to complete the search string | |
259 | using the search ring as a list of completion alternatives. | |
260 | @xref{Completion}. In many operating systems, the @kbd{M-@key{TAB}} | |
261 | key sequence is captured by the window manager; you then need to | |
262 | rebind @code{isearch-complete} to another key sequence if you want to | |
263 | use it (@pxref{Rebinding}). | |
264 | ||
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265 | @vindex isearch-mode-map |
266 | When incremental search is active, you can type @kbd{C-h C-h} to | |
267 | access interactive help options, including a list of special | |
268 | keybindings. These keybindings are part of the keymap | |
269 | @code{isearch-mode-map} (@pxref{Keymaps}). | |
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270 | |
271 | @node Isearch Yank | |
272 | @subsection Isearch Yanking | |
273 | ||
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274 | Within incremental search, you can use @kbd{C-w} and @kbd{C-y} to grab |
275 | text from the buffer into the search string. This makes it convenient | |
276 | to search for another occurrence of text at point. | |
277 | ||
278 | @kbd{C-w} copies the character or word after point and adds it to | |
279 | the search string, advancing point over it. (The decision, whether to | |
280 | copy a character or a word, is heuristic.) | |
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281 | |
282 | @kbd{C-y} is similar to @kbd{C-w} but copies all the rest of the | |
283 | current line into the search string. If point is already at the end | |
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284 | of a line, it grabs the entire next line. If the search is currently |
285 | case-insensitive, both @kbd{C-y} and @kbd{C-w} convert the text they | |
286 | copy to lower case, so that the search remains case-insensitive. | |
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287 | |
288 | @kbd{C-M-w} and @kbd{C-M-y} modify the search string by only one | |
289 | character at a time: @kbd{C-M-w} deletes the last character from the | |
290 | search string and @kbd{C-M-y} copies the character after point to the | |
291 | end of the search string. An alternative method to add the character | |
292 | after point into the search string is to enter the minibuffer by | |
293 | @kbd{M-e} and to type @kbd{C-f} at the end of the search string in the | |
294 | minibuffer. | |
295 | ||
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296 | The character @kbd{M-y} copies text from the kill ring into the |
297 | search string. It uses the same text that @kbd{C-y} would yank. | |
298 | @kbd{Mouse-2} in the echo area does the same. @xref{Yanking}. | |
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299 | |
300 | @node Isearch Scroll | |
301 | @subsection Scrolling During Incremental Search | |
302 | ||
40e67246 | 303 | @vindex isearch-allow-scroll |
8cf51b2c GM |
304 | You can enable the use of vertical scrolling during incremental |
305 | search (without exiting the search) by setting the customizable | |
306 | variable @code{isearch-allow-scroll} to a non-@code{nil} value. This | |
307 | applies to using the vertical scroll-bar and to certain keyboard | |
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308 | commands such as @key{prior} (@code{scroll-down}), @key{next} |
309 | (@code{scroll-up}) and @kbd{C-l} (@code{recenter}). You must run | |
310 | these commands via their key sequences to stay in the search---typing | |
311 | @kbd{M-x} will terminate the search. You can give prefix arguments to | |
312 | these commands in the usual way. | |
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313 | |
314 | This feature won't let you scroll the current match out of visibility, | |
315 | however. | |
316 | ||
317 | The feature also affects some other commands, such as @kbd{C-x 2} | |
318 | (@code{split-window-vertically}) and @kbd{C-x ^} | |
319 | (@code{enlarge-window}) which don't exactly scroll but do affect where | |
320 | the text appears on the screen. In general, it applies to any command | |
321 | whose name has a non-@code{nil} @code{isearch-scroll} property. So you | |
322 | can control which commands are affected by changing these properties. | |
323 | ||
324 | For example, to make @kbd{C-h l} usable within an incremental search | |
325 | in all future Emacs sessions, use @kbd{C-h c} to find what command it | |
326 | runs. (You type @kbd{C-h c C-h l}; it says @code{view-lossage}.) | |
327 | Then you can put the following line in your @file{.emacs} file | |
328 | (@pxref{Init File}): | |
329 | ||
330 | @example | |
331 | (put 'view-lossage 'isearch-scroll t) | |
332 | @end example | |
333 | ||
334 | @noindent | |
335 | This feature can be applied to any command that doesn't permanently | |
336 | change point, the buffer contents, the match data, the current buffer, | |
337 | or the selected window and frame. The command must not itself attempt | |
338 | an incremental search. | |
339 | ||
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340 | @node Isearch Minibuffer |
341 | @subsection Searching the Minibuffer | |
342 | @cindex minibuffer history, searching | |
343 | ||
344 | If you start an incremental search while the minibuffer is active, | |
345 | Emacs searches the contents of the minibuffer. Unlike searching an | |
346 | ordinary buffer, the search string is not shown in the echo area, | |
347 | because that is used to display the minibuffer. | |
348 | ||
349 | If an incremental search fails in the minibuffer, it tries searching | |
350 | the minibuffer history. @xref{Minibuffer History}. You can visualize | |
351 | the minibuffer and its history as a series of ``pages'', with the | |
352 | earliest history element on the first page and the current minibuffer | |
353 | on the last page. A forward search, @kbd{C-s}, searches forward to | |
354 | later pages; a reverse search, @kbd{C-r}, searches backwards to | |
355 | earlier pages. Like in ordinary buffer search, a failing search can | |
356 | wrap around, going from the last page to the first page or vice versa. | |
357 | ||
358 | When the current match is on a history element, that history element | |
359 | is pulled into the minibuffer. If you exit the incremental search | |
360 | normally (e.g. by typing @key{RET}), it remains in the minibuffer | |
361 | afterwards. Cancelling the search, with @kbd{C-g}, restores the | |
362 | contents of the minibuffer when you began the search. | |
363 | ||
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364 | @node Slow Isearch |
365 | @subsection Slow Terminal Incremental Search | |
366 | ||
367 | Incremental search on a slow terminal uses a modified style of display | |
368 | that is designed to take less time. Instead of redisplaying the buffer at | |
369 | each place the search gets to, it creates a new single-line window and uses | |
370 | that to display the line that the search has found. The single-line window | |
371 | comes into play as soon as point moves outside of the text that is already | |
372 | on the screen. | |
373 | ||
374 | When you terminate the search, the single-line window is removed. | |
375 | Emacs then redisplays the window in which the search was done, to show | |
376 | its new position of point. | |
377 | ||
378 | @vindex search-slow-speed | |
379 | The slow terminal style of display is used when the terminal baud rate is | |
380 | less than or equal to the value of the variable @code{search-slow-speed}, | |
381 | initially 1200. See also the discussion of the variable @code{baud-rate} | |
382 | (@pxref{baud-rate,, Customization of Display}). | |
383 | ||
384 | @vindex search-slow-window-lines | |
385 | The number of lines to use in slow terminal search display is controlled | |
386 | by the variable @code{search-slow-window-lines}. Its normal value is 1. | |
387 | ||
388 | @node Nonincremental Search | |
389 | @section Nonincremental Search | |
390 | @cindex nonincremental search | |
391 | ||
392 | Emacs also has conventional nonincremental search commands, which require | |
393 | you to type the entire search string before searching begins. | |
394 | ||
395 | @table @kbd | |
396 | @item C-s @key{RET} @var{string} @key{RET} | |
397 | Search for @var{string}. | |
398 | @item C-r @key{RET} @var{string} @key{RET} | |
399 | Search backward for @var{string}. | |
400 | @end table | |
401 | ||
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402 | To start a nonincremental search, first type @kbd{C-s @key{RET}}. |
403 | This enters the minibuffer to read the search string; terminate the | |
404 | string with @key{RET}, and then the search takes place. If the string | |
405 | is not found, the search command signals an error. | |
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406 | |
407 | When you type @kbd{C-s @key{RET}}, the @kbd{C-s} invokes incremental | |
408 | search as usual. That command is specially programmed to invoke | |
409 | nonincremental search, @code{search-forward}, if the string you | |
410 | specify is empty. (Such an empty argument would otherwise be | |
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411 | useless.) @kbd{C-r @key{RET}} does likewise, for a reverse |
412 | incremental search. | |
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413 | |
414 | @findex search-forward | |
415 | @findex search-backward | |
416 | Forward and backward nonincremental searches are implemented by the | |
417 | commands @code{search-forward} and @code{search-backward}. These | |
b5fb9df5 | 418 | commands may be bound to other keys in the usual manner. |
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419 | |
420 | @node Word Search | |
421 | @section Word Search | |
422 | @cindex word search | |
423 | ||
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424 | A @dfn{word search} finds a sequence of words without regard to the |
425 | type of punctuation between them. For instance, if you enter a search | |
426 | string that consists of two words separated by a single space, the | |
427 | search matches any sequence of those two words separated by one or | |
428 | more spaces, newlines, or other punctuation characters. This is | |
429 | particularly useful for searching text documents, because you don't | |
430 | have to worry whether the words you are looking for are separated by | |
431 | newlines or spaces. | |
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432 | |
433 | @table @kbd | |
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434 | @item M-s w |
435 | If incremental search is active, toggle word search mode | |
436 | (@code{isearch-toggle-word}); otherwise, begin an incremental forward | |
437 | word search (@code{isearch-forward-word}). | |
97b3a00b JL |
438 | @item M-s w @key{RET} @var{words} @key{RET} |
439 | Search for @var{words}, using a forward nonincremental word search. | |
440 | @item M-s w C-r @key{RET} @var{words} @key{RET} | |
441 | Search backward for @var{words}, using a nonincremental word search. | |
8cf51b2c GM |
442 | @end table |
443 | ||
97b3a00b JL |
444 | @kindex M-s w |
445 | @findex isearch-forward-word | |
b5fb9df5 CY |
446 | To begin a forward incremental word search, type @kbd{M-s w}. If |
447 | incremental search is not already active, this runs the command | |
448 | @code{isearch-forward-word}. If incremental search is already active | |
449 | (whether a forward or backward search), @kbd{M-s w} switches to a word | |
450 | search while keeping the direction of the search and the current | |
451 | search string unchanged. You can toggle word search back off by | |
452 | typing @kbd{M-s w} again. | |
8cf51b2c GM |
453 | |
454 | @findex word-search-forward | |
455 | @findex word-search-backward | |
97b3a00b JL |
456 | To begin a nonincremental word search, type @kbd{M-s w @key{RET}} |
457 | for a forward search, or @kbd{M-s w C-r @key{RET}} for a backward search. | |
b5fb9df5 CY |
458 | These run the commands @code{word-search-forward} and |
459 | @code{word-search-backward} respectively. | |
460 | ||
461 | A nonincremental word search differs slightly from the incremental | |
462 | version in the way it finds a match: the last word in the search | |
463 | string must be an exact match for a whole word. In an incremental | |
464 | word search, the last word in the search string can match part of a | |
465 | word; this allows the matching to proceed incrementally as you type. | |
8cf51b2c GM |
466 | |
467 | @node Regexp Search | |
468 | @section Regular Expression Search | |
469 | @cindex regular expression | |
470 | @cindex regexp | |
471 | ||
b5fb9df5 CY |
472 | A @dfn{regular expression} (or @dfn{regexp} for short) is a pattern |
473 | that denotes a class of alternative strings to match. GNU Emacs | |
474 | provides both incremental and nonincremental ways to search for a | |
475 | match for a regexp. The syntax of regular expressions is explained in | |
476 | the following section. | |
8cf51b2c | 477 | |
97b3a00b JL |
478 | @table @kbd |
479 | @item C-M-s | |
480 | Begin incremental regexp search (@code{isearch-forward-regexp}). | |
481 | @item C-M-r | |
482 | Begin reverse incremental regexp search (@code{isearch-backward-regexp}). | |
483 | @end table | |
484 | ||
8cf51b2c GM |
485 | @kindex C-M-s |
486 | @findex isearch-forward-regexp | |
487 | @kindex C-M-r | |
488 | @findex isearch-backward-regexp | |
489 | Incremental search for a regexp is done by typing @kbd{C-M-s} | |
490 | (@code{isearch-forward-regexp}), by invoking @kbd{C-s} with a | |
491 | prefix argument (whose value does not matter), or by typing @kbd{M-r} | |
492 | within a forward incremental search. This command reads a | |
493 | search string incrementally just like @kbd{C-s}, but it treats the | |
494 | search string as a regexp rather than looking for an exact match | |
495 | against the text in the buffer. Each time you add text to the search | |
496 | string, you make the regexp longer, and the new regexp is searched | |
497 | for. To search backward for a regexp, use @kbd{C-M-r} | |
498 | (@code{isearch-backward-regexp}), @kbd{C-r} with a prefix argument, | |
499 | or @kbd{M-r} within a backward incremental search. | |
500 | ||
b5fb9df5 CY |
501 | All of the special key sequences in an ordinary incremental search |
502 | do similar things in an incremental regexp search. For instance, | |
503 | typing @kbd{C-s} immediately after starting the search retrieves the | |
504 | last incremental search regexp used and searches forward for it. | |
505 | Incremental regexp and non-regexp searches have independent defaults. | |
506 | They also have separate search rings, which you can access with | |
8cf51b2c GM |
507 | @kbd{M-p} and @kbd{M-n}. |
508 | ||
509 | @vindex search-whitespace-regexp | |
510 | If you type @key{SPC} in incremental regexp search, it matches any | |
511 | sequence of whitespace characters, including newlines. If you want to | |
512 | match just a space, type @kbd{C-q @key{SPC}}. You can control what a | |
513 | bare space matches by setting the variable | |
514 | @code{search-whitespace-regexp} to the desired regexp. | |
515 | ||
b5fb9df5 CY |
516 | In some cases, adding characters to the regexp in an incremental |
517 | regexp search can make the cursor move back and start again. For | |
518 | example, if you have searched for @samp{foo} and you add @samp{\|bar}, | |
519 | the cursor backs up in case the first @samp{bar} precedes the first | |
520 | @samp{foo}. @xref{Regexps}. | |
8cf51b2c GM |
521 | |
522 | Forward and backward regexp search are not symmetrical, because | |
523 | regexp matching in Emacs always operates forward, starting with the | |
524 | beginning of the regexp. Thus, forward regexp search scans forward, | |
525 | trying a forward match at each possible starting position. Backward | |
526 | regexp search scans backward, trying a forward match at each possible | |
527 | starting position. These search methods are not mirror images. | |
528 | ||
529 | @findex re-search-forward | |
530 | @findex re-search-backward | |
531 | Nonincremental search for a regexp is done by the functions | |
b5fb9df5 CY |
532 | @code{re-search-forward} and @code{re-search-backward}. You can |
533 | invoke these with @kbd{M-x}, or by way of incremental regexp search | |
534 | with @kbd{C-M-s @key{RET}} and @kbd{C-M-r @key{RET}}. | |
8cf51b2c GM |
535 | |
536 | If you use the incremental regexp search commands with a prefix | |
537 | argument, they perform ordinary string search, like | |
538 | @code{isearch-forward} and @code{isearch-backward}. @xref{Incremental | |
539 | Search}. | |
540 | ||
541 | @node Regexps | |
542 | @section Syntax of Regular Expressions | |
543 | @cindex syntax of regexps | |
544 | ||
545 | This manual describes regular expression features that users | |
546 | typically want to use. There are additional features that are | |
547 | mainly used in Lisp programs; see @ref{Regular Expressions,,, | |
548 | elisp, The Emacs Lisp Reference Manual}. | |
549 | ||
550 | Regular expressions have a syntax in which a few characters are | |
551 | special constructs and the rest are @dfn{ordinary}. An ordinary | |
552 | character is a simple regular expression which matches that same | |
553 | character and nothing else. The special characters are @samp{$}, | |
554 | @samp{^}, @samp{.}, @samp{*}, @samp{+}, @samp{?}, @samp{[}, and | |
555 | @samp{\}. The character @samp{]} is special if it ends a character | |
556 | alternative (see later). The character @samp{-} is special inside a | |
557 | character alternative. Any other character appearing in a regular | |
558 | expression is ordinary, unless a @samp{\} precedes it. (When you use | |
559 | regular expressions in a Lisp program, each @samp{\} must be doubled, | |
560 | see the example near the end of this section.) | |
561 | ||
562 | For example, @samp{f} is not a special character, so it is ordinary, and | |
563 | therefore @samp{f} is a regular expression that matches the string | |
564 | @samp{f} and no other string. (It does @emph{not} match the string | |
565 | @samp{ff}.) Likewise, @samp{o} is a regular expression that matches | |
566 | only @samp{o}. (When case distinctions are being ignored, these regexps | |
567 | also match @samp{F} and @samp{O}, but we consider this a generalization | |
568 | of ``the same string,'' rather than an exception.) | |
569 | ||
570 | Any two regular expressions @var{a} and @var{b} can be concatenated. The | |
571 | result is a regular expression which matches a string if @var{a} matches | |
572 | some amount of the beginning of that string and @var{b} matches the rest of | |
573 | the string.@refill | |
574 | ||
575 | As a simple example, we can concatenate the regular expressions @samp{f} | |
576 | and @samp{o} to get the regular expression @samp{fo}, which matches only | |
577 | the string @samp{fo}. Still trivial. To do something nontrivial, you | |
578 | need to use one of the special characters. Here is a list of them. | |
579 | ||
580 | @table @asis | |
581 | @item @kbd{.}@: @r{(Period)} | |
582 | is a special character that matches any single character except a newline. | |
583 | Using concatenation, we can make regular expressions like @samp{a.b}, which | |
584 | matches any three-character string that begins with @samp{a} and ends with | |
585 | @samp{b}.@refill | |
586 | ||
587 | @item @kbd{*} | |
588 | is not a construct by itself; it is a postfix operator that means to | |
589 | match the preceding regular expression repetitively as many times as | |
590 | possible. Thus, @samp{o*} matches any number of @samp{o}s (including no | |
591 | @samp{o}s). | |
592 | ||
593 | @samp{*} always applies to the @emph{smallest} possible preceding | |
594 | expression. Thus, @samp{fo*} has a repeating @samp{o}, not a repeating | |
595 | @samp{fo}. It matches @samp{f}, @samp{fo}, @samp{foo}, and so on. | |
596 | ||
597 | The matcher processes a @samp{*} construct by matching, immediately, | |
598 | as many repetitions as can be found. Then it continues with the rest | |
599 | of the pattern. If that fails, backtracking occurs, discarding some | |
600 | of the matches of the @samp{*}-modified construct in case that makes | |
601 | it possible to match the rest of the pattern. For example, in matching | |
602 | @samp{ca*ar} against the string @samp{caaar}, the @samp{a*} first | |
603 | tries to match all three @samp{a}s; but the rest of the pattern is | |
604 | @samp{ar} and there is only @samp{r} left to match, so this try fails. | |
605 | The next alternative is for @samp{a*} to match only two @samp{a}s. | |
606 | With this choice, the rest of the regexp matches successfully.@refill | |
607 | ||
608 | @item @kbd{+} | |
609 | is a postfix operator, similar to @samp{*} except that it must match | |
610 | the preceding expression at least once. So, for example, @samp{ca+r} | |
611 | matches the strings @samp{car} and @samp{caaaar} but not the string | |
612 | @samp{cr}, whereas @samp{ca*r} matches all three strings. | |
613 | ||
614 | @item @kbd{?} | |
615 | is a postfix operator, similar to @samp{*} except that it can match the | |
616 | preceding expression either once or not at all. For example, | |
617 | @samp{ca?r} matches @samp{car} or @samp{cr}; nothing else. | |
618 | ||
619 | @item @kbd{*?}, @kbd{+?}, @kbd{??} | |
620 | @cindex non-greedy regexp matching | |
621 | are non-greedy variants of the operators above. The normal operators | |
622 | @samp{*}, @samp{+}, @samp{?} are @dfn{greedy} in that they match as | |
623 | much as they can, as long as the overall regexp can still match. With | |
624 | a following @samp{?}, they are non-greedy: they will match as little | |
625 | as possible. | |
626 | ||
627 | Thus, both @samp{ab*} and @samp{ab*?} can match the string @samp{a} | |
628 | and the string @samp{abbbb}; but if you try to match them both against | |
629 | the text @samp{abbb}, @samp{ab*} will match it all (the longest valid | |
630 | match), while @samp{ab*?} will match just @samp{a} (the shortest | |
631 | valid match). | |
632 | ||
633 | Non-greedy operators match the shortest possible string starting at a | |
634 | given starting point; in a forward search, though, the earliest | |
635 | possible starting point for match is always the one chosen. Thus, if | |
636 | you search for @samp{a.*?$} against the text @samp{abbab} followed by | |
637 | a newline, it matches the whole string. Since it @emph{can} match | |
638 | starting at the first @samp{a}, it does. | |
639 | ||
640 | @item @kbd{\@{@var{n}\@}} | |
641 | is a postfix operator that specifies repetition @var{n} times---that | |
642 | is, the preceding regular expression must match exactly @var{n} times | |
643 | in a row. For example, @samp{x\@{4\@}} matches the string @samp{xxxx} | |
644 | and nothing else. | |
645 | ||
646 | @item @kbd{\@{@var{n},@var{m}\@}} | |
647 | is a postfix operator that specifies repetition between @var{n} and | |
648 | @var{m} times---that is, the preceding regular expression must match | |
649 | at least @var{n} times, but no more than @var{m} times. If @var{m} is | |
650 | omitted, then there is no upper limit, but the preceding regular | |
651 | expression must match at least @var{n} times.@* @samp{\@{0,1\@}} is | |
652 | equivalent to @samp{?}. @* @samp{\@{0,\@}} is equivalent to | |
653 | @samp{*}. @* @samp{\@{1,\@}} is equivalent to @samp{+}. | |
654 | ||
655 | @item @kbd{[ @dots{} ]} | |
656 | is a @dfn{character set}, which begins with @samp{[} and is terminated | |
657 | by @samp{]}. In the simplest case, the characters between the two | |
658 | brackets are what this set can match. | |
659 | ||
660 | Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and | |
661 | @samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s | |
662 | (including the empty string), from which it follows that @samp{c[ad]*r} | |
663 | matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc. | |
664 | ||
665 | You can also include character ranges in a character set, by writing the | |
666 | starting and ending characters with a @samp{-} between them. Thus, | |
667 | @samp{[a-z]} matches any lower-case @acronym{ASCII} letter. Ranges may be | |
668 | intermixed freely with individual characters, as in @samp{[a-z$%.]}, | |
669 | which matches any lower-case @acronym{ASCII} letter or @samp{$}, @samp{%} or | |
670 | period. | |
671 | ||
672 | Note that the usual regexp special characters are not special inside a | |
673 | character set. A completely different set of special characters exists | |
674 | inside character sets: @samp{]}, @samp{-} and @samp{^}. | |
675 | ||
676 | To include a @samp{]} in a character set, you must make it the first | |
677 | character. For example, @samp{[]a]} matches @samp{]} or @samp{a}. To | |
678 | include a @samp{-}, write @samp{-} as the first or last character of the | |
679 | set, or put it after a range. Thus, @samp{[]-]} matches both @samp{]} | |
680 | and @samp{-}. | |
681 | ||
682 | To include @samp{^} in a set, put it anywhere but at the beginning of | |
683 | the set. (At the beginning, it complements the set---see below.) | |
684 | ||
685 | When you use a range in case-insensitive search, you should write both | |
686 | ends of the range in upper case, or both in lower case, or both should | |
687 | be non-letters. The behavior of a mixed-case range such as @samp{A-z} | |
688 | is somewhat ill-defined, and it may change in future Emacs versions. | |
689 | ||
690 | @item @kbd{[^ @dots{} ]} | |
691 | @samp{[^} begins a @dfn{complemented character set}, which matches any | |
692 | character except the ones specified. Thus, @samp{[^a-z0-9A-Z]} matches | |
693 | all characters @emph{except} @acronym{ASCII} letters and digits. | |
694 | ||
695 | @samp{^} is not special in a character set unless it is the first | |
696 | character. The character following the @samp{^} is treated as if it | |
697 | were first (in other words, @samp{-} and @samp{]} are not special there). | |
698 | ||
699 | A complemented character set can match a newline, unless newline is | |
700 | mentioned as one of the characters not to match. This is in contrast to | |
701 | the handling of regexps in programs such as @code{grep}. | |
702 | ||
703 | @item @kbd{^} | |
704 | is a special character that matches the empty string, but only at the | |
705 | beginning of a line in the text being matched. Otherwise it fails to | |
706 | match anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at | |
707 | the beginning of a line. | |
708 | ||
709 | For historical compatibility reasons, @samp{^} can be used with this | |
710 | meaning only at the beginning of the regular expression, or after | |
711 | @samp{\(} or @samp{\|}. | |
712 | ||
713 | @item @kbd{$} | |
714 | is similar to @samp{^} but matches only at the end of a line. Thus, | |
715 | @samp{x+$} matches a string of one @samp{x} or more at the end of a line. | |
716 | ||
717 | For historical compatibility reasons, @samp{$} can be used with this | |
718 | meaning only at the end of the regular expression, or before @samp{\)} | |
719 | or @samp{\|}. | |
720 | ||
721 | @item @kbd{\} | |
722 | has two functions: it quotes the special characters (including | |
723 | @samp{\}), and it introduces additional special constructs. | |
724 | ||
725 | Because @samp{\} quotes special characters, @samp{\$} is a regular | |
726 | expression that matches only @samp{$}, and @samp{\[} is a regular | |
727 | expression that matches only @samp{[}, and so on. | |
728 | ||
729 | See the following section for the special constructs that begin | |
730 | with @samp{\}. | |
731 | @end table | |
732 | ||
733 | Note: for historical compatibility, special characters are treated as | |
734 | ordinary ones if they are in contexts where their special meanings make no | |
735 | sense. For example, @samp{*foo} treats @samp{*} as ordinary since there is | |
736 | no preceding expression on which the @samp{*} can act. It is poor practice | |
737 | to depend on this behavior; it is better to quote the special character anyway, | |
738 | regardless of where it appears. | |
739 | ||
740 | As a @samp{\} is not special inside a character alternative, it can | |
741 | never remove the special meaning of @samp{-} or @samp{]}. So you | |
742 | should not quote these characters when they have no special meaning | |
743 | either. This would not clarify anything, since backslashes can | |
744 | legitimately precede these characters where they @emph{have} special | |
745 | meaning, as in @samp{[^\]} (@code{"[^\\]"} for Lisp string syntax), | |
746 | which matches any single character except a backslash. | |
747 | ||
748 | @node Regexp Backslash | |
749 | @section Backslash in Regular Expressions | |
750 | ||
751 | For the most part, @samp{\} followed by any character matches only | |
752 | that character. However, there are several exceptions: two-character | |
753 | sequences starting with @samp{\} that have special meanings. The | |
754 | second character in the sequence is always an ordinary character when | |
755 | used on its own. Here is a table of @samp{\} constructs. | |
756 | ||
757 | @table @kbd | |
758 | @item \| | |
759 | specifies an alternative. Two regular expressions @var{a} and @var{b} | |
760 | with @samp{\|} in between form an expression that matches some text if | |
761 | either @var{a} matches it or @var{b} matches it. It works by trying to | |
762 | match @var{a}, and if that fails, by trying to match @var{b}. | |
763 | ||
764 | Thus, @samp{foo\|bar} matches either @samp{foo} or @samp{bar} | |
765 | but no other string.@refill | |
766 | ||
767 | @samp{\|} applies to the largest possible surrounding expressions. Only a | |
768 | surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of | |
769 | @samp{\|}.@refill | |
770 | ||
771 | Full backtracking capability exists to handle multiple uses of @samp{\|}. | |
772 | ||
773 | @item \( @dots{} \) | |
774 | is a grouping construct that serves three purposes: | |
775 | ||
776 | @enumerate | |
777 | @item | |
778 | To enclose a set of @samp{\|} alternatives for other operations. | |
779 | Thus, @samp{\(foo\|bar\)x} matches either @samp{foox} or @samp{barx}. | |
780 | ||
781 | @item | |
782 | To enclose a complicated expression for the postfix operators @samp{*}, | |
783 | @samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches | |
784 | @samp{bananana}, etc., with any (zero or more) number of @samp{na} | |
785 | strings.@refill | |
786 | ||
787 | @item | |
788 | To record a matched substring for future reference. | |
789 | @end enumerate | |
790 | ||
791 | This last application is not a consequence of the idea of a | |
792 | parenthetical grouping; it is a separate feature that is assigned as a | |
793 | second meaning to the same @samp{\( @dots{} \)} construct. In practice | |
794 | there is usually no conflict between the two meanings; when there is | |
795 | a conflict, you can use a ``shy'' group. | |
796 | ||
797 | @item \(?: @dots{} \) | |
798 | @cindex shy group, in regexp | |
799 | specifies a ``shy'' group that does not record the matched substring; | |
800 | you can't refer back to it with @samp{\@var{d}}. This is useful | |
801 | in mechanically combining regular expressions, so that you | |
802 | can add groups for syntactic purposes without interfering with | |
803 | the numbering of the groups that are meant to be referred to. | |
804 | ||
805 | @item \@var{d} | |
806 | @cindex back reference, in regexp | |
807 | matches the same text that matched the @var{d}th occurrence of a | |
808 | @samp{\( @dots{} \)} construct. This is called a @dfn{back | |
809 | reference}. | |
810 | ||
811 | After the end of a @samp{\( @dots{} \)} construct, the matcher remembers | |
812 | the beginning and end of the text matched by that construct. Then, | |
813 | later on in the regular expression, you can use @samp{\} followed by the | |
814 | digit @var{d} to mean ``match the same text matched the @var{d}th time | |
815 | by the @samp{\( @dots{} \)} construct.'' | |
816 | ||
817 | The strings matching the first nine @samp{\( @dots{} \)} constructs | |
818 | appearing in a regular expression are assigned numbers 1 through 9 in | |
819 | the order that the open-parentheses appear in the regular expression. | |
820 | So you can use @samp{\1} through @samp{\9} to refer to the text matched | |
821 | by the corresponding @samp{\( @dots{} \)} constructs. | |
822 | ||
823 | For example, @samp{\(.*\)\1} matches any newline-free string that is | |
824 | composed of two identical halves. The @samp{\(.*\)} matches the first | |
825 | half, which may be anything, but the @samp{\1} that follows must match | |
826 | the same exact text. | |
827 | ||
828 | If a particular @samp{\( @dots{} \)} construct matches more than once | |
829 | (which can easily happen if it is followed by @samp{*}), only the last | |
830 | match is recorded. | |
831 | ||
832 | @item \` | |
833 | matches the empty string, but only at the beginning of the string or | |
834 | buffer (or its accessible portion) being matched against. | |
835 | ||
836 | @item \' | |
837 | matches the empty string, but only at the end of the string or buffer | |
838 | (or its accessible portion) being matched against. | |
839 | ||
840 | @item \= | |
841 | matches the empty string, but only at point. | |
842 | ||
843 | @item \b | |
844 | matches the empty string, but only at the beginning or | |
845 | end of a word. Thus, @samp{\bfoo\b} matches any occurrence of | |
846 | @samp{foo} as a separate word. @samp{\bballs?\b} matches | |
847 | @samp{ball} or @samp{balls} as a separate word.@refill | |
848 | ||
849 | @samp{\b} matches at the beginning or end of the buffer | |
850 | regardless of what text appears next to it. | |
851 | ||
852 | @item \B | |
853 | matches the empty string, but @emph{not} at the beginning or | |
854 | end of a word. | |
855 | ||
856 | @item \< | |
857 | matches the empty string, but only at the beginning of a word. | |
858 | @samp{\<} matches at the beginning of the buffer only if a | |
859 | word-constituent character follows. | |
860 | ||
861 | @item \> | |
862 | matches the empty string, but only at the end of a word. @samp{\>} | |
863 | matches at the end of the buffer only if the contents end with a | |
864 | word-constituent character. | |
865 | ||
866 | @item \w | |
867 | matches any word-constituent character. The syntax table | |
868 | determines which characters these are. @xref{Syntax}. | |
869 | ||
870 | @item \W | |
871 | matches any character that is not a word-constituent. | |
872 | ||
873 | @item \_< | |
874 | matches the empty string, but only at the beginning of a symbol. | |
875 | A symbol is a sequence of one or more symbol-constituent characters. | |
876 | A symbol-constituent character is a character whose syntax is either | |
877 | @samp{w} or @samp{_}. @samp{\_<} matches at the beginning of the | |
878 | buffer only if a symbol-constituent character follows. | |
879 | ||
880 | @item \_> | |
881 | matches the empty string, but only at the end of a symbol. @samp{\_>} | |
882 | matches at the end of the buffer only if the contents end with a | |
883 | symbol-constituent character. | |
884 | ||
885 | @item \s@var{c} | |
886 | matches any character whose syntax is @var{c}. Here @var{c} is a | |
887 | character that designates a particular syntax class: thus, @samp{w} | |
888 | for word constituent, @samp{-} or @samp{ } for whitespace, @samp{.} | |
889 | for ordinary punctuation, etc. @xref{Syntax}. | |
890 | ||
891 | @item \S@var{c} | |
892 | matches any character whose syntax is not @var{c}. | |
893 | ||
894 | @cindex categories of characters | |
895 | @cindex characters which belong to a specific language | |
896 | @findex describe-categories | |
897 | @item \c@var{c} | |
898 | matches any character that belongs to the category @var{c}. For | |
899 | example, @samp{\cc} matches Chinese characters, @samp{\cg} matches | |
900 | Greek characters, etc. For the description of the known categories, | |
901 | type @kbd{M-x describe-categories @key{RET}}. | |
902 | ||
903 | @item \C@var{c} | |
904 | matches any character that does @emph{not} belong to category | |
905 | @var{c}. | |
906 | @end table | |
907 | ||
908 | The constructs that pertain to words and syntax are controlled by the | |
909 | setting of the syntax table (@pxref{Syntax}). | |
910 | ||
911 | @node Regexp Example | |
912 | @section Regular Expression Example | |
913 | ||
b5fb9df5 CY |
914 | Here is an example of a regexp---the regexp that Emacs uses, by |
915 | default, to recognize the end of a sentence, not including the | |
916 | following space (i.e., the variable @code{sentence-end-base}): | |
8cf51b2c GM |
917 | |
918 | @example | |
b5fb9df5 CY |
919 | @verbatim |
920 | [.?!][]\"'””)}]* | |
921 | @end verbatim | |
8cf51b2c GM |
922 | @end example |
923 | ||
924 | @noindent | |
b5fb9df5 CY |
925 | This contains two parts in succession: a character set matching |
926 | period, @samp{?}, or @samp{!}, and a character set matching | |
927 | close-brackets, quotes, or parentheses, repeated zero or more times. | |
8cf51b2c GM |
928 | |
929 | @node Search Case | |
930 | @section Searching and Case | |
931 | ||
b5fb9df5 CY |
932 | Searches in Emacs normally ignore the case of the text they are |
933 | searching through, if you specify the text in lower case. Thus, if | |
934 | you specify searching for @samp{foo}, then @samp{Foo} and @samp{foo} | |
935 | are also considered a match. Regexps, and in particular character | |
936 | sets, are included: @samp{[ab]} would match @samp{a} or @samp{A} or | |
937 | @samp{b} or @samp{B}.@refill | |
8cf51b2c GM |
938 | |
939 | An upper-case letter anywhere in the incremental search string makes | |
940 | the search case-sensitive. Thus, searching for @samp{Foo} does not find | |
941 | @samp{foo} or @samp{FOO}. This applies to regular expression search as | |
942 | well as to string search. The effect ceases if you delete the | |
943 | upper-case letter from the search string. | |
944 | ||
945 | Typing @kbd{M-c} within an incremental search toggles the case | |
946 | sensitivity of that search. The effect does not extend beyond the | |
947 | current incremental search to the next one, but it does override the | |
b5fb9df5 CY |
948 | effect of adding or removing an upper-case letter in the current |
949 | search. | |
8cf51b2c GM |
950 | |
951 | @vindex case-fold-search | |
8cf51b2c GM |
952 | If you set the variable @code{case-fold-search} to @code{nil}, then |
953 | all letters must match exactly, including case. This is a per-buffer | |
4e3b4528 SM |
954 | variable; altering the variable normally affects only the current buffer, |
955 | unless you change its default value. @xref{Locals}. | |
956 | This variable applies to nonincremental searches also, including those | |
957 | performed by the replace commands (@pxref{Replace}) and the minibuffer | |
958 | history matching commands (@pxref{Minibuffer History}). | |
8cf51b2c GM |
959 | |
960 | Several related variables control case-sensitivity of searching and | |
961 | matching for specific commands or activities. For instance, | |
962 | @code{tags-case-fold-search} controls case sensitivity for | |
963 | @code{find-tag}. To find these variables, do @kbd{M-x | |
964 | apropos-variable @key{RET} case-fold-search @key{RET}}. | |
965 | ||
966 | @node Replace | |
967 | @section Replacement Commands | |
968 | @cindex replacement | |
969 | @cindex search-and-replace commands | |
970 | @cindex string substitution | |
971 | @cindex global substitution | |
972 | ||
b5fb9df5 CY |
973 | Emacs provides several commands for performing search-and-replace |
974 | operations. In addition to the simple @kbd{M-x replace-string} | |
975 | command, there is @kbd{M-%} (@code{query-replace}), which presents | |
976 | each occurrence of the pattern and asks you whether to replace it. | |
8cf51b2c GM |
977 | |
978 | The replace commands normally operate on the text from point to the | |
6184c708 CY |
979 | end of the buffer. When the mark is active, they operate on the |
980 | region instead (@pxref{Mark}). The basic replace commands replace one | |
b5fb9df5 CY |
981 | @dfn{search string} (or regexp) with one @dfn{replacement string}. It |
982 | is possible to perform several replacements in parallel, using the | |
983 | command @code{expand-region-abbrevs} (@pxref{Expanding Abbrevs}). | |
8cf51b2c GM |
984 | |
985 | @menu | |
986 | * Unconditional Replace:: Replacing all matches for a string. | |
987 | * Regexp Replace:: Replacing all matches for a regexp. | |
988 | * Replacement and Case:: How replacements preserve case of letters. | |
989 | * Query Replace:: How to use querying. | |
990 | @end menu | |
991 | ||
992 | @node Unconditional Replace, Regexp Replace, Replace, Replace | |
993 | @subsection Unconditional Replacement | |
994 | @findex replace-string | |
995 | ||
996 | @table @kbd | |
997 | @item M-x replace-string @key{RET} @var{string} @key{RET} @var{newstring} @key{RET} | |
998 | Replace every occurrence of @var{string} with @var{newstring}. | |
999 | @end table | |
1000 | ||
1001 | To replace every instance of @samp{foo} after point with @samp{bar}, | |
1002 | use the command @kbd{M-x replace-string} with the two arguments | |
1003 | @samp{foo} and @samp{bar}. Replacement happens only in the text after | |
1004 | point, so if you want to cover the whole buffer you must go to the | |
1005 | beginning first. All occurrences up to the end of the buffer are | |
b5fb9df5 CY |
1006 | replaced; to limit replacement to part of the buffer, activate the |
1007 | region around that part. When the region is active, replacement is | |
1008 | limited to the region (@pxref{Mark}). | |
8cf51b2c GM |
1009 | |
1010 | When @code{replace-string} exits, it leaves point at the last | |
6184c708 CY |
1011 | occurrence replaced. It adds the prior position of point (where the |
1012 | @code{replace-string} command was issued) to the mark ring, without | |
1013 | activating the mark; use @kbd{C-u C-@key{SPC}} to move back there. | |
1014 | @xref{Mark Ring}. | |
8cf51b2c | 1015 | |
b5fb9df5 CY |
1016 | A prefix argument restricts replacement to matches that are |
1017 | surrounded by word boundaries. The argument's value doesn't matter. | |
8cf51b2c GM |
1018 | |
1019 | @xref{Replacement and Case}, for details about case-sensitivity in | |
1020 | replace commands. | |
1021 | ||
8cf51b2c GM |
1022 | @node Regexp Replace, Replacement and Case, Unconditional Replace, Replace |
1023 | @subsection Regexp Replacement | |
1024 | @findex replace-regexp | |
1025 | ||
1026 | The @kbd{M-x replace-string} command replaces exact matches for a | |
1027 | single string. The similar command @kbd{M-x replace-regexp} replaces | |
1028 | any match for a specified pattern. | |
1029 | ||
1030 | @table @kbd | |
1031 | @item M-x replace-regexp @key{RET} @var{regexp} @key{RET} @var{newstring} @key{RET} | |
1032 | Replace every match for @var{regexp} with @var{newstring}. | |
1033 | @end table | |
1034 | ||
1035 | @cindex back reference, in regexp replacement | |
1036 | In @code{replace-regexp}, the @var{newstring} need not be constant: | |
1037 | it can refer to all or part of what is matched by the @var{regexp}. | |
1038 | @samp{\&} in @var{newstring} stands for the entire match being | |
1039 | replaced. @samp{\@var{d}} in @var{newstring}, where @var{d} is a | |
1040 | digit, stands for whatever matched the @var{d}th parenthesized | |
1041 | grouping in @var{regexp}. (This is called a ``back reference.'') | |
1042 | @samp{\#} refers to the count of replacements already made in this | |
1043 | command, as a decimal number. In the first replacement, @samp{\#} | |
1044 | stands for @samp{0}; in the second, for @samp{1}; and so on. For | |
1045 | example, | |
1046 | ||
1047 | @example | |
1048 | M-x replace-regexp @key{RET} c[ad]+r @key{RET} \&-safe @key{RET} | |
1049 | @end example | |
1050 | ||
1051 | @noindent | |
1052 | replaces (for example) @samp{cadr} with @samp{cadr-safe} and @samp{cddr} | |
1053 | with @samp{cddr-safe}. | |
1054 | ||
1055 | @example | |
1056 | M-x replace-regexp @key{RET} \(c[ad]+r\)-safe @key{RET} \1 @key{RET} | |
1057 | @end example | |
1058 | ||
1059 | @noindent | |
1060 | performs the inverse transformation. To include a @samp{\} in the | |
1061 | text to replace with, you must enter @samp{\\}. | |
1062 | ||
1063 | If you want to enter part of the replacement string by hand each | |
1064 | time, use @samp{\?} in the replacement string. Each replacement will | |
1065 | ask you to edit the replacement string in the minibuffer, putting | |
1066 | point where the @samp{\?} was. | |
1067 | ||
1068 | The remainder of this subsection is intended for specialized tasks | |
1069 | and requires knowledge of Lisp. Most readers can skip it. | |
1070 | ||
1071 | You can use Lisp expressions to calculate parts of the | |
1072 | replacement string. To do this, write @samp{\,} followed by the | |
1073 | expression in the replacement string. Each replacement calculates the | |
1074 | value of the expression and converts it to text without quoting (if | |
1075 | it's a string, this means using the string's contents), and uses it in | |
1076 | the replacement string in place of the expression itself. If the | |
1077 | expression is a symbol, one space in the replacement string after the | |
1078 | symbol name goes with the symbol name, so the value replaces them | |
1079 | both. | |
1080 | ||
1081 | Inside such an expression, you can use some special sequences. | |
1082 | @samp{\&} and @samp{\@var{n}} refer here, as usual, to the entire | |
1083 | match as a string, and to a submatch as a string. @var{n} may be | |
1084 | multiple digits, and the value of @samp{\@var{n}} is @code{nil} if | |
1085 | subexpression @var{n} did not match. You can also use @samp{\#&} and | |
1086 | @samp{\#@var{n}} to refer to those matches as numbers (this is valid | |
1087 | when the match or submatch has the form of a numeral). @samp{\#} here | |
1088 | too stands for the number of already-completed replacements. | |
1089 | ||
1090 | Repeating our example to exchange @samp{x} and @samp{y}, we can thus | |
1091 | do it also this way: | |
1092 | ||
1093 | @example | |
1094 | M-x replace-regexp @key{RET} \(x\)\|y @key{RET} | |
1095 | \,(if \1 "y" "x") @key{RET} | |
1096 | @end example | |
1097 | ||
1098 | For computing replacement strings for @samp{\,}, the @code{format} | |
1099 | function is often useful (@pxref{Formatting Strings,,, elisp, The Emacs | |
1100 | Lisp Reference Manual}). For example, to add consecutively numbered | |
1101 | strings like @samp{ABC00042} to columns 73 @w{to 80} (unless they are | |
1102 | already occupied), you can use | |
1103 | ||
1104 | @example | |
1105 | M-x replace-regexp @key{RET} ^.\@{0,72\@}$ @key{RET} | |
1106 | \,(format "%-72sABC%05d" \& \#) @key{RET} | |
1107 | @end example | |
1108 | ||
1109 | @node Replacement and Case, Query Replace, Regexp Replace, Replace | |
1110 | @subsection Replace Commands and Case | |
1111 | ||
1112 | If the first argument of a replace command is all lower case, the | |
1113 | command ignores case while searching for occurrences to | |
1114 | replace---provided @code{case-fold-search} is non-@code{nil}. If | |
1115 | @code{case-fold-search} is set to @code{nil}, case is always significant | |
1116 | in all searches. | |
1117 | ||
1118 | @vindex case-replace | |
1119 | In addition, when the @var{newstring} argument is all or partly lower | |
1120 | case, replacement commands try to preserve the case pattern of each | |
1121 | occurrence. Thus, the command | |
1122 | ||
1123 | @example | |
1124 | M-x replace-string @key{RET} foo @key{RET} bar @key{RET} | |
1125 | @end example | |
1126 | ||
1127 | @noindent | |
1128 | replaces a lower case @samp{foo} with a lower case @samp{bar}, an | |
1129 | all-caps @samp{FOO} with @samp{BAR}, and a capitalized @samp{Foo} with | |
1130 | @samp{Bar}. (These three alternatives---lower case, all caps, and | |
1131 | capitalized, are the only ones that @code{replace-string} can | |
1132 | distinguish.) | |
1133 | ||
1134 | If upper-case letters are used in the replacement string, they remain | |
1135 | upper case every time that text is inserted. If upper-case letters are | |
1136 | used in the first argument, the second argument is always substituted | |
1137 | exactly as given, with no case conversion. Likewise, if either | |
1138 | @code{case-replace} or @code{case-fold-search} is set to @code{nil}, | |
1139 | replacement is done without case conversion. | |
1140 | ||
1141 | @node Query Replace,, Replacement and Case, Replace | |
1142 | @subsection Query Replace | |
1143 | @cindex query replace | |
1144 | ||
1145 | @table @kbd | |
1146 | @item M-% @var{string} @key{RET} @var{newstring} @key{RET} | |
1147 | @itemx M-x query-replace @key{RET} @var{string} @key{RET} @var{newstring} @key{RET} | |
1148 | Replace some occurrences of @var{string} with @var{newstring}. | |
1149 | @item C-M-% @var{regexp} @key{RET} @var{newstring} @key{RET} | |
1150 | @itemx M-x query-replace-regexp @key{RET} @var{regexp} @key{RET} @var{newstring} @key{RET} | |
1151 | Replace some matches for @var{regexp} with @var{newstring}. | |
1152 | @end table | |
1153 | ||
1154 | @kindex M-% | |
1155 | @findex query-replace | |
1156 | If you want to change only some of the occurrences of @samp{foo} to | |
abfd0191 | 1157 | @samp{bar}, not all of them, use @kbd{M-%} (@code{query-replace}). |
8cf51b2c GM |
1158 | This command finds occurrences of @samp{foo} one by one, displays each |
1159 | occurrence and asks you whether to replace it. Aside from querying, | |
abfd0191 RS |
1160 | @code{query-replace} works just like @code{replace-string} |
1161 | (@pxref{Unconditional Replace}). In particular, it preserves case | |
1162 | provided @code{case-replace} is non-@code{nil}, as it normally is | |
8cf51b2c GM |
1163 | (@pxref{Replacement and Case}). A numeric argument means consider |
1164 | only occurrences that are bounded by word-delimiter characters. | |
1165 | ||
1166 | @kindex C-M-% | |
1167 | @findex query-replace-regexp | |
1168 | @kbd{C-M-%} performs regexp search and replace (@code{query-replace-regexp}). | |
1169 | It works like @code{replace-regexp} except that it queries | |
1170 | like @code{query-replace}. | |
1171 | ||
1172 | @cindex faces for highlighting query replace | |
1173 | These commands highlight the current match using the face | |
1174 | @code{query-replace}. They highlight other matches using | |
1175 | @code{lazy-highlight} just like incremental search (@pxref{Incremental | |
21d50ba1 JL |
1176 | Search}). By default, @code{query-replace-regexp} will show |
1177 | substituted replacement string for the current match in the | |
1178 | minibuffer. If you want to keep special sequences @samp{\&} and | |
1179 | @samp{\@var{n}} unexpanded, customize | |
1180 | @code{query-replace-show-replacement} variable. | |
8cf51b2c GM |
1181 | |
1182 | The characters you can type when you are shown a match for the string | |
1183 | or regexp are: | |
1184 | ||
1185 | @ignore @c Not worth it. | |
1186 | @kindex SPC @r{(query-replace)} | |
1187 | @kindex DEL @r{(query-replace)} | |
1188 | @kindex , @r{(query-replace)} | |
1189 | @kindex RET @r{(query-replace)} | |
1190 | @kindex . @r{(query-replace)} | |
1191 | @kindex ! @r{(query-replace)} | |
1192 | @kindex ^ @r{(query-replace)} | |
1193 | @kindex C-r @r{(query-replace)} | |
1194 | @kindex C-w @r{(query-replace)} | |
1195 | @kindex C-l @r{(query-replace)} | |
1196 | @end ignore | |
1197 | ||
1198 | @c WideCommands | |
1199 | @table @kbd | |
1200 | @item @key{SPC} | |
1201 | to replace the occurrence with @var{newstring}. | |
1202 | ||
1203 | @item @key{DEL} | |
1204 | to skip to the next occurrence without replacing this one. | |
1205 | ||
1206 | @item , @r{(Comma)} | |
1207 | to replace this occurrence and display the result. You are then asked | |
1208 | for another input character to say what to do next. Since the | |
1209 | replacement has already been made, @key{DEL} and @key{SPC} are | |
1210 | equivalent in this situation; both move to the next occurrence. | |
1211 | ||
1212 | You can type @kbd{C-r} at this point (see below) to alter the replaced | |
1213 | text. You can also type @kbd{C-x u} to undo the replacement; this exits | |
1214 | the @code{query-replace}, so if you want to do further replacement you | |
1215 | must use @kbd{C-x @key{ESC} @key{ESC} @key{RET}} to restart | |
1216 | (@pxref{Repetition}). | |
1217 | ||
1218 | @item @key{RET} | |
1219 | to exit without doing any more replacements. | |
1220 | ||
1221 | @item .@: @r{(Period)} | |
1222 | to replace this occurrence and then exit without searching for more | |
1223 | occurrences. | |
1224 | ||
1225 | @item ! | |
1226 | to replace all remaining occurrences without asking again. | |
1227 | ||
1228 | @item ^ | |
1229 | to go back to the position of the previous occurrence (or what used to | |
1230 | be an occurrence), in case you changed it by mistake or want to | |
1231 | reexamine it. | |
1232 | ||
1233 | @item C-r | |
1234 | to enter a recursive editing level, in case the occurrence needs to be | |
1235 | edited rather than just replaced with @var{newstring}. When you are | |
1236 | done, exit the recursive editing level with @kbd{C-M-c} to proceed to | |
1237 | the next occurrence. @xref{Recursive Edit}. | |
1238 | ||
1239 | @item C-w | |
1240 | to delete the occurrence, and then enter a recursive editing level as in | |
1241 | @kbd{C-r}. Use the recursive edit to insert text to replace the deleted | |
1242 | occurrence of @var{string}. When done, exit the recursive editing level | |
1243 | with @kbd{C-M-c} to proceed to the next occurrence. | |
1244 | ||
1245 | @item e | |
1246 | to edit the replacement string in the minibuffer. When you exit the | |
1247 | minibuffer by typing @key{RET}, the minibuffer contents replace the | |
1248 | current occurrence of the pattern. They also become the new | |
1249 | replacement string for any further occurrences. | |
1250 | ||
1251 | @item C-l | |
1252 | to redisplay the screen. Then you must type another character to | |
1253 | specify what to do with this occurrence. | |
1254 | ||
1255 | @item C-h | |
1256 | to display a message summarizing these options. Then you must type | |
1257 | another character to specify what to do with this occurrence. | |
1258 | @end table | |
1259 | ||
1260 | Some other characters are aliases for the ones listed above: @kbd{y}, | |
1261 | @kbd{n} and @kbd{q} are equivalent to @key{SPC}, @key{DEL} and | |
1262 | @key{RET}. | |
1263 | ||
1264 | Aside from this, any other character exits the @code{query-replace}, | |
1265 | and is then reread as part of a key sequence. Thus, if you type | |
1266 | @kbd{C-k}, it exits the @code{query-replace} and then kills to end of | |
1267 | line. | |
1268 | ||
1269 | To restart a @code{query-replace} once it is exited, use @kbd{C-x | |
1270 | @key{ESC} @key{ESC}}, which repeats the @code{query-replace} because it | |
1271 | used the minibuffer to read its arguments. @xref{Repetition, C-x ESC | |
1272 | ESC}. | |
1273 | ||
1274 | @xref{Operating on Files}, for the Dired @kbd{Q} command which | |
1275 | performs query replace on selected files. See also @ref{Transforming | |
1276 | File Names}, for Dired commands to rename, copy, or link files by | |
1277 | replacing regexp matches in file names. | |
1278 | ||
1279 | @node Other Repeating Search | |
1280 | @section Other Search-and-Loop Commands | |
1281 | ||
1282 | Here are some other commands that find matches for a regular | |
1283 | expression. They all ignore case in matching, if the pattern contains | |
1284 | no upper-case letters and @code{case-fold-search} is non-@code{nil}. | |
1285 | Aside from @code{occur} and its variants, all operate on the text from | |
6184c708 | 1286 | point to the end of the buffer, or on the region if it is active. |
8cf51b2c GM |
1287 | |
1288 | @findex list-matching-lines | |
1289 | @findex occur | |
1290 | @findex multi-occur | |
1291 | @findex multi-occur-in-matching-buffers | |
1292 | @findex how-many | |
8cf51b2c GM |
1293 | @findex flush-lines |
1294 | @findex keep-lines | |
1295 | ||
1296 | @table @kbd | |
1297 | @item M-x occur @key{RET} @var{regexp} @key{RET} | |
1298 | Display a list showing each line in the buffer that contains a match | |
1299 | for @var{regexp}. To limit the search to part of the buffer, narrow | |
1300 | to that part (@pxref{Narrowing}). A numeric argument @var{n} | |
1301 | specifies that @var{n} lines of context are to be displayed before and | |
1302 | after each matching line. Currently, @code{occur} can not correctly | |
1303 | handle multiline matches. | |
1304 | ||
1305 | @kindex RET @r{(Occur mode)} | |
1306 | @kindex o @r{(Occur mode)} | |
1307 | @kindex C-o @r{(Occur mode)} | |
1308 | The buffer @samp{*Occur*} containing the output serves as a menu for | |
1309 | finding the occurrences in their original context. Click | |
1310 | @kbd{Mouse-2} on an occurrence listed in @samp{*Occur*}, or position | |
1311 | point there and type @key{RET}; this switches to the buffer that was | |
1312 | searched and moves point to the original of the chosen occurrence. | |
1313 | @kbd{o} and @kbd{C-o} display the match in another window; @kbd{C-o} | |
1314 | does not select it. | |
1315 | ||
1316 | After using @kbd{M-x occur}, you can use @code{next-error} to visit | |
1317 | the occurrences found, one by one. @ref{Compilation Mode}. | |
1318 | ||
b5fb9df5 CY |
1319 | @kindex M-s o |
1320 | @item M-s o | |
1321 | Run @code{occur} using the search string of the last incremental | |
97b3a00b | 1322 | string search. You can also run @kbd{M-s o} when an incremental |
b5fb9df5 CY |
1323 | search is active; this uses the current search string. |
1324 | ||
8cf51b2c GM |
1325 | @item M-x list-matching-lines |
1326 | Synonym for @kbd{M-x occur}. | |
1327 | ||
1328 | @item M-x multi-occur @key{RET} @var{buffers} @key{RET} @var{regexp} @key{RET} | |
1329 | This function is just like @code{occur}, except it is able to search | |
1330 | through multiple buffers. It asks you to specify the buffer names one by one. | |
1331 | ||
1332 | @item M-x multi-occur-in-matching-buffers @key{RET} @var{bufregexp} @key{RET} @var{regexp} @key{RET} | |
1333 | This function is similar to @code{multi-occur}, except the buffers to | |
1334 | search are specified by a regular expression that matches visited | |
1335 | file names. With a prefix argument, it uses the regular expression to match | |
1336 | buffer names instead. | |
1337 | ||
1338 | @item M-x how-many @key{RET} @var{regexp} @key{RET} | |
1339 | Print the number of matches for @var{regexp} that exist in the buffer | |
6184c708 CY |
1340 | after point. If the region is active, this operates on the region |
1341 | instead. | |
8cf51b2c GM |
1342 | |
1343 | @item M-x flush-lines @key{RET} @var{regexp} @key{RET} | |
1344 | This command deletes each line that contains a match for @var{regexp}, | |
6184c708 CY |
1345 | operating on the text after point; it deletes the current line if it |
1346 | contains a match starting after point. If the region is active, it | |
1347 | operates on the region instead; if a line partially contained in the | |
1348 | region contains a match entirely contained in the region, it is | |
1349 | deleted. | |
8cf51b2c GM |
1350 | |
1351 | If a match is split across lines, @code{flush-lines} deletes all those | |
1352 | lines. It deletes the lines before starting to look for the next | |
1353 | match; hence, it ignores a match starting on the same line at which | |
1354 | another match ended. | |
1355 | ||
1356 | @item M-x keep-lines @key{RET} @var{regexp} @key{RET} | |
6184c708 CY |
1357 | This command deletes each line that @emph{does not} contain a match |
1358 | for @var{regexp}, operating on the text after point; if point is not | |
1359 | at the beginning of a line, it always keeps the current line. If the | |
1360 | region is active, the command operates on the region instead; it never | |
1361 | deletes lines that are only partially contained in the region (a | |
1362 | newline that ends a line counts as part of that line). | |
8cf51b2c GM |
1363 | |
1364 | If a match is split across lines, this command keeps all those lines. | |
1365 | @end table | |
1366 | ||
1367 | @ignore | |
1368 | arch-tag: fd9d8e77-66af-491c-b212-d80999613e3e | |
1369 | @end ignore |