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129 | .\" ======================================================================== | |
130 | .\" | |
131 | .IX Title "PERLREREF 1" | |
132 | .TH PERLREREF 1 "2006-01-07" "perl v5.8.8" "Perl Programmers Reference Guide" | |
133 | .SH "NAME" | |
134 | perlreref \- Perl Regular Expressions Reference | |
135 | .SH "DESCRIPTION" | |
136 | .IX Header "DESCRIPTION" | |
137 | This is a quick reference to Perl's regular expressions. | |
138 | For full information see perlre and perlop, as well | |
139 | as the \*(L"\s-1SEE\s0 \s-1ALSO\s0\*(R" section in this document. | |
140 | .Sh "\s-1OPERATORS\s0" | |
141 | .IX Subsection "OPERATORS" | |
142 | .Vb 2 | |
143 | \& =~ determines to which variable the regex is applied. | |
144 | \& In its absence, $_ is used. | |
145 | .Ve | |
146 | .PP | |
147 | .Vb 1 | |
148 | \& $var =~ /foo/; | |
149 | .Ve | |
150 | .PP | |
151 | .Vb 3 | |
152 | \& !~ determines to which variable the regex is applied, | |
153 | \& and negates the result of the match; it returns | |
154 | \& false if the match succeeds, and true if it fails. | |
155 | .Ve | |
156 | .PP | |
157 | .Vb 1 | |
158 | \& $var !~ /foo/; | |
159 | .Ve | |
160 | .PP | |
161 | .Vb 2 | |
162 | \& m/pattern/igmsoxc searches a string for a pattern match, | |
163 | \& applying the given options. | |
164 | .Ve | |
165 | .PP | |
166 | .Vb 7 | |
167 | \& i case-Insensitive | |
168 | \& g Global - all occurrences | |
169 | \& m Multiline mode - ^ and $ match internal lines | |
170 | \& s match as a Single line - . matches \en | |
171 | \& o compile pattern Once | |
172 | \& x eXtended legibility - free whitespace and comments | |
173 | \& c don't reset pos on failed matches when using /g | |
174 | .Ve | |
175 | .PP | |
176 | .Vb 3 | |
177 | \& If 'pattern' is an empty string, the last I<successfully> matched | |
178 | \& regex is used. Delimiters other than '/' may be used for both this | |
179 | \& operator and the following ones. | |
180 | .Ve | |
181 | .PP | |
182 | .Vb 3 | |
183 | \& qr/pattern/imsox lets you store a regex in a variable, | |
184 | \& or pass one around. Modifiers as for m// and are stored | |
185 | \& within the regex. | |
186 | .Ve | |
187 | .PP | |
188 | .Vb 3 | |
189 | \& s/pattern/replacement/igmsoxe substitutes matches of | |
190 | \& 'pattern' with 'replacement'. Modifiers as for m// | |
191 | \& with one addition: | |
192 | .Ve | |
193 | .PP | |
194 | .Vb 1 | |
195 | \& e Evaluate replacement as an expression | |
196 | .Ve | |
197 | .PP | |
198 | .Vb 2 | |
199 | \& 'e' may be specified multiple times. 'replacement' is interpreted | |
200 | \& as a double quoted string unless a single-quote (') is the delimiter. | |
201 | .Ve | |
202 | .PP | |
203 | .Vb 2 | |
204 | \& ?pattern? is like m/pattern/ but matches only once. No alternate | |
205 | \& delimiters can be used. Must be reset with L<reset|perlfunc/reset>. | |
206 | .Ve | |
207 | .Sh "\s-1SYNTAX\s0" | |
208 | .IX Subsection "SYNTAX" | |
209 | .Vb 13 | |
210 | \& \e Escapes the character immediately following it | |
211 | \& . Matches any single character except a newline (unless /s is used) | |
212 | \& ^ Matches at the beginning of the string (or line, if /m is used) | |
213 | \& $ Matches at the end of the string (or line, if /m is used) | |
214 | \& * Matches the preceding element 0 or more times | |
215 | \& + Matches the preceding element 1 or more times | |
216 | \& ? Matches the preceding element 0 or 1 times | |
217 | \& {...} Specifies a range of occurrences for the element preceding it | |
218 | \& [...] Matches any one of the characters contained within the brackets | |
219 | \& (...) Groups subexpressions for capturing to $1, $2... | |
220 | \& (?:...) Groups subexpressions without capturing (cluster) | |
221 | \& | Matches either the subexpression preceding or following it | |
222 | \& \e1, \e2 ... The text from the Nth group | |
223 | .Ve | |
224 | .Sh "\s-1ESCAPE\s0 \s-1SEQUENCES\s0" | |
225 | .IX Subsection "ESCAPE SEQUENCES" | |
226 | These work as in normal strings. | |
227 | .PP | |
228 | .Vb 11 | |
229 | \& \ea Alarm (beep) | |
230 | \& \ee Escape | |
231 | \& \ef Formfeed | |
232 | \& \en Newline | |
233 | \& \er Carriage return | |
234 | \& \et Tab | |
235 | \& \e037 Any octal ASCII value | |
236 | \& \ex7f Any hexadecimal ASCII value | |
237 | \& \ex{263a} A wide hexadecimal value | |
238 | \& \ecx Control-x | |
239 | \& \eN{name} A named character | |
240 | .Ve | |
241 | .PP | |
242 | .Vb 6 | |
243 | \& \el Lowercase next character | |
244 | \& \eu Titlecase next character | |
245 | \& \eL Lowercase until \eE | |
246 | \& \eU Uppercase until \eE | |
247 | \& \eQ Disable pattern metacharacters until \eE | |
248 | \& \eE End case modification | |
249 | .Ve | |
250 | .PP | |
251 | For Titlecase, see \*(L"Titlecase\*(R". | |
252 | .PP | |
253 | This one works differently from normal strings: | |
254 | .PP | |
255 | .Vb 1 | |
256 | \& \eb An assertion, not backspace, except in a character class | |
257 | .Ve | |
258 | .Sh "\s-1CHARACTER\s0 \s-1CLASSES\s0" | |
259 | .IX Subsection "CHARACTER CLASSES" | |
260 | .Vb 4 | |
261 | \& [amy] Match 'a', 'm' or 'y' | |
262 | \& [f-j] Dash specifies "range" | |
263 | \& [f-j-] Dash escaped or at start or end means 'dash' | |
264 | \& [^f-j] Caret indicates "match any character _except_ these" | |
265 | .Ve | |
266 | .PP | |
267 | The following sequences work within or without a character class. | |
268 | The first six are locale aware, all are Unicode aware. The default | |
269 | character class equivalent are given. See perllocale and | |
270 | perlunicode for details. | |
271 | .PP | |
272 | .Vb 6 | |
273 | \& \ed A digit [0-9] | |
274 | \& \eD A nondigit [^0-9] | |
275 | \& \ew A word character [a-zA-Z0-9_] | |
276 | \& \eW A non-word character [^a-zA-Z0-9_] | |
277 | \& \es A whitespace character [ \et\en\er\ef] | |
278 | \& \eS A non-whitespace character [^ \et\en\er\ef] | |
279 | .Ve | |
280 | .PP | |
281 | .Vb 6 | |
282 | \& \eC Match a byte (with Unicode, '.' matches a character) | |
283 | \& \epP Match P-named (Unicode) property | |
284 | \& \ep{...} Match Unicode property with long name | |
285 | \& \ePP Match non-P | |
286 | \& \eP{...} Match lack of Unicode property with long name | |
287 | \& \eX Match extended unicode sequence | |
288 | .Ve | |
289 | .PP | |
290 | \&\s-1POSIX\s0 character classes and their Unicode and Perl equivalents: | |
291 | .PP | |
292 | .Vb 15 | |
293 | \& alnum IsAlnum Alphanumeric | |
294 | \& alpha IsAlpha Alphabetic | |
295 | \& ascii IsASCII Any ASCII char | |
296 | \& blank IsSpace [ \et] Horizontal whitespace (GNU extension) | |
297 | \& cntrl IsCntrl Control characters | |
298 | \& digit IsDigit \ed Digits | |
299 | \& graph IsGraph Alphanumeric and punctuation | |
300 | \& lower IsLower Lowercase chars (locale and Unicode aware) | |
301 | \& print IsPrint Alphanumeric, punct, and space | |
302 | \& punct IsPunct Punctuation | |
303 | \& space IsSpace [\es\eck] Whitespace | |
304 | \& IsSpacePerl \es Perl's whitespace definition | |
305 | \& upper IsUpper Uppercase chars (locale and Unicode aware) | |
306 | \& word IsWord \ew Alphanumeric plus _ (Perl extension) | |
307 | \& xdigit IsXDigit [0-9A-Fa-f] Hexadecimal digit | |
308 | .Ve | |
309 | .PP | |
310 | Within a character class: | |
311 | .PP | |
312 | .Vb 3 | |
313 | \& POSIX traditional Unicode | |
314 | \& [:digit:] \ed \ep{IsDigit} | |
315 | \& [:^digit:] \eD \eP{IsDigit} | |
316 | .Ve | |
317 | .Sh "\s-1ANCHORS\s0" | |
318 | .IX Subsection "ANCHORS" | |
319 | All are zero-width assertions. | |
320 | .PP | |
321 | .Vb 8 | |
322 | \& ^ Match string start (or line, if /m is used) | |
323 | \& $ Match string end (or line, if /m is used) or before newline | |
324 | \& \eb Match word boundary (between \ew and \eW) | |
325 | \& \eB Match except at word boundary (between \ew and \ew or \eW and \eW) | |
326 | \& \eA Match string start (regardless of /m) | |
327 | \& \eZ Match string end (before optional newline) | |
328 | \& \ez Match absolute string end | |
329 | \& \eG Match where previous m//g left off | |
330 | .Ve | |
331 | .Sh "\s-1QUANTIFIERS\s0" | |
332 | .IX Subsection "QUANTIFIERS" | |
333 | Quantifiers are greedy by default \*(-- match the \fBlongest\fR leftmost. | |
334 | .PP | |
335 | .Vb 8 | |
336 | \& Maximal Minimal Allowed range | |
337 | \& ------- ------- ------------- | |
338 | \& {n,m} {n,m}? Must occur at least n times but no more than m times | |
339 | \& {n,} {n,}? Must occur at least n times | |
340 | \& {n} {n}? Must occur exactly n times | |
341 | \& * *? 0 or more times (same as {0,}) | |
342 | \& + +? 1 or more times (same as {1,}) | |
343 | \& ? ?? 0 or 1 time (same as {0,1}) | |
344 | .Ve | |
345 | .PP | |
346 | There is no quantifier {,n} \*(-- that gets understood as a literal string. | |
347 | .Sh "\s-1EXTENDED\s0 \s-1CONSTRUCTS\s0" | |
348 | .IX Subsection "EXTENDED CONSTRUCTS" | |
349 | .Vb 11 | |
350 | \& (?#text) A comment | |
351 | \& (?imxs-imsx:...) Enable/disable option (as per m// modifiers) | |
352 | \& (?=...) Zero-width positive lookahead assertion | |
353 | \& (?!...) Zero-width negative lookahead assertion | |
354 | \& (?<=...) Zero-width positive lookbehind assertion | |
355 | \& (?<!...) Zero-width negative lookbehind assertion | |
356 | \& (?>...) Grab what we can, prohibit backtracking | |
357 | \& (?{ code }) Embedded code, return value becomes $^R | |
358 | \& (??{ code }) Dynamic regex, return value used as regex | |
359 | \& (?(cond)yes|no) cond being integer corresponding to capturing parens | |
360 | \& (?(cond)yes) or a lookaround/eval zero-width assertion | |
361 | .Ve | |
362 | .Sh "\s-1VARIABLES\s0" | |
363 | .IX Subsection "VARIABLES" | |
364 | .Vb 2 | |
365 | \& $_ Default variable for operators to use | |
366 | \& $* Enable multiline matching (deprecated; not in 5.9.0 or later) | |
367 | .Ve | |
368 | .PP | |
369 | .Vb 3 | |
370 | \& $& Entire matched string | |
371 | \& $` Everything prior to matched string | |
372 | \& $' Everything after to matched string | |
373 | .Ve | |
374 | .PP | |
375 | The use of those last three will slow down \fBall\fR regex use | |
376 | within your program. Consult perlvar for \f(CW@LAST_MATCH_START\fR | |
377 | to see equivalent expressions that won't cause slow down. | |
378 | See also Devel::SawAmpersand. | |
379 | .PP | |
380 | .Vb 6 | |
381 | \& $1, $2 ... hold the Xth captured expr | |
382 | \& $+ Last parenthesized pattern match | |
383 | \& $^N Holds the most recently closed capture | |
384 | \& $^R Holds the result of the last (?{...}) expr | |
385 | \& @- Offsets of starts of groups. $-[0] holds start of whole match | |
386 | \& @+ Offsets of ends of groups. $+[0] holds end of whole match | |
387 | .Ve | |
388 | .PP | |
389 | Captured groups are numbered according to their \fIopening\fR paren. | |
390 | .Sh "\s-1FUNCTIONS\s0" | |
391 | .IX Subsection "FUNCTIONS" | |
392 | .Vb 4 | |
393 | \& lc Lowercase a string | |
394 | \& lcfirst Lowercase first char of a string | |
395 | \& uc Uppercase a string | |
396 | \& ucfirst Titlecase first char of a string | |
397 | .Ve | |
398 | .PP | |
399 | .Vb 4 | |
400 | \& pos Return or set current match position | |
401 | \& quotemeta Quote metacharacters | |
402 | \& reset Reset ?pattern? status | |
403 | \& study Analyze string for optimizing matching | |
404 | .Ve | |
405 | .PP | |
406 | .Vb 1 | |
407 | \& split Use regex to split a string into parts | |
408 | .Ve | |
409 | .PP | |
410 | The first four of these are like the escape sequences \f(CW\*(C`\eL\*(C'\fR, \f(CW\*(C`\el\*(C'\fR, | |
411 | \&\f(CW\*(C`\eU\*(C'\fR, and \f(CW\*(C`\eu\*(C'\fR. For Titlecase, see \*(L"Titlecase\*(R". | |
412 | .Sh "\s-1TERMINOLOGY\s0" | |
413 | .IX Subsection "TERMINOLOGY" | |
414 | \fITitlecase\fR | |
415 | .IX Subsection "Titlecase" | |
416 | .PP | |
417 | Unicode concept which most often is equal to uppercase, but for | |
418 | certain characters like the German \*(L"sharp s\*(R" there is a difference. | |
419 | .SH "AUTHOR" | |
420 | .IX Header "AUTHOR" | |
421 | Iain Truskett. | |
422 | .PP | |
423 | This document may be distributed under the same terms as Perl itself. | |
424 | .SH "SEE ALSO" | |
425 | .IX Header "SEE ALSO" | |
426 | .IP "\(bu" 4 | |
427 | perlretut for a tutorial on regular expressions. | |
428 | .IP "\(bu" 4 | |
429 | perlrequick for a rapid tutorial. | |
430 | .IP "\(bu" 4 | |
431 | perlre for more details. | |
432 | .IP "\(bu" 4 | |
433 | perlvar for details on the variables. | |
434 | .IP "\(bu" 4 | |
435 | perlop for details on the operators. | |
436 | .IP "\(bu" 4 | |
437 | perlfunc for details on the functions. | |
438 | .IP "\(bu" 4 | |
439 | perlfaq6 for FAQs on regular expressions. | |
440 | .IP "\(bu" 4 | |
441 | The re module to alter behaviour and aid | |
442 | debugging. | |
443 | .IP "\(bu" 4 | |
444 | \&\*(L"Debugging regular expressions\*(R" in perldebug | |
445 | .IP "\(bu" 4 | |
446 | perluniintro, perlunicode, charnames and locale | |
447 | for details on regexes and internationalisation. | |
448 | .IP "\(bu" 4 | |
449 | \&\fIMastering Regular Expressions\fR by Jeffrey Friedl | |
450 | (\fIhttp://regex.info/\fR) for a thorough grounding and | |
451 | reference on the topic. | |
452 | .SH "THANKS" | |
453 | .IX Header "THANKS" | |
454 | David P.C. Wollmann, | |
455 | Richard Soderberg, | |
456 | Sean M. Burke, | |
457 | Tom Christiansen, | |
458 | Jim Cromie, | |
459 | and | |
460 | Jeffrey Goff | |
461 | for useful advice. |