3 <title>pcresyntax specification</title>
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6 <h1>pcresyntax man page</h1>
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16 <li><a name="TOC1" href="#SEC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a>
17 <li><a name="TOC2" href="#SEC2">QUOTING</a>
18 <li><a name="TOC3" href="#SEC3">CHARACTERS</a>
19 <li><a name="TOC4" href="#SEC4">CHARACTER TYPES</a>
20 <li><a name="TOC5" href="#SEC5">GENERAL CATEGORY PROPERTIES FOR \p and \P</a>
21 <li><a name="TOC6" href="#SEC6">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a>
22 <li><a name="TOC7" href="#SEC7">SCRIPT NAMES FOR \p AND \P</a>
23 <li><a name="TOC8" href="#SEC8">CHARACTER CLASSES</a>
24 <li><a name="TOC9" href="#SEC9">QUANTIFIERS</a>
25 <li><a name="TOC10" href="#SEC10">ANCHORS AND SIMPLE ASSERTIONS</a>
26 <li><a name="TOC11" href="#SEC11">MATCH POINT RESET</a>
27 <li><a name="TOC12" href="#SEC12">ALTERNATION</a>
28 <li><a name="TOC13" href="#SEC13">CAPTURING</a>
29 <li><a name="TOC14" href="#SEC14">ATOMIC GROUPS</a>
30 <li><a name="TOC15" href="#SEC15">COMMENT</a>
31 <li><a name="TOC16" href="#SEC16">OPTION SETTING</a>
32 <li><a name="TOC17" href="#SEC17">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
33 <li><a name="TOC18" href="#SEC18">BACKREFERENCES</a>
34 <li><a name="TOC19" href="#SEC19">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
35 <li><a name="TOC20" href="#SEC20">CONDITIONAL PATTERNS</a>
36 <li><a name="TOC21" href="#SEC21">BACKTRACKING CONTROL</a>
37 <li><a name="TOC22" href="#SEC22">NEWLINE CONVENTIONS</a>
38 <li><a name="TOC23" href="#SEC23">WHAT \R MATCHES</a>
39 <li><a name="TOC24" href="#SEC24">CALLOUTS</a>
40 <li><a name="TOC25" href="#SEC25">SEE ALSO</a>
41 <li><a name="TOC26" href="#SEC26">AUTHOR</a>
42 <li><a name="TOC27" href="#SEC27">REVISION</a>
44 <br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
46 The full syntax and semantics of the regular expressions that are supported by
47 PCRE are described in the
48 <a href="pcrepattern.html"><b>pcrepattern</b></a>
49 documentation. This document contains just a quick-reference summary of the
52 <br><a name="SEC2" href="#TOC1">QUOTING</a><br>
55 \x where x is non-alphanumeric is a literal x
56 \Q...\E treat enclosed characters as literal
59 <br><a name="SEC3" href="#TOC1">CHARACTERS</a><br>
62 \a alarm, that is, the BEL character (hex 07)
63 \cx "control-x", where x is any ASCII character
67 \r carriage return (hex 0D)
69 \ddd character with octal code ddd, or backreference
70 \xhh character with hex code hh
71 \x{hhh..} character with hex code hhh..
74 <br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br>
77 . any character except newline;
78 in dotall mode, any character whatsoever
79 \C one byte, even in UTF-8 mode (best avoided)
81 \D a character that is not a decimal digit
82 \h a horizontal whitespace character
83 \H a character that is not a horizontal whitespace character
84 \N a character that is not a newline
85 \p{<i>xx</i>} a character with the <i>xx</i> property
86 \P{<i>xx</i>} a character without the <i>xx</i> property
88 \s a whitespace character
89 \S a character that is not a whitespace character
90 \v a vertical whitespace character
91 \V a character that is not a vertical whitespace character
93 \W a "non-word" character
94 \X an extended Unicode sequence
96 In PCRE, by default, \d, \D, \s, \S, \w, and \W recognize only ASCII
97 characters, even in UTF-8 mode. However, this can be changed by setting the
100 <br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a><br>
129 Pc Connector punctuation
133 Pi Initial punctuation
140 Sm Mathematical symbol
145 Zp Paragraph separator
149 <br><a name="SEC6" href="#TOC1">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br>
152 Xan Alphanumeric: union of properties L and N
153 Xps POSIX space: property Z or tab, NL, VT, FF, CR
154 Xsp Perl space: property Z or tab, NL, FF, CR
155 Xwd Perl word: property Xan or underscore
158 <br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
181 Egyptian_Hieroglyphs,
196 Inscriptional_Pahlavi,
197 Inscriptional_Parthian,
253 <br><a name="SEC8" href="#TOC1">CHARACTER CLASSES</a><br>
256 [...] positive character class
257 [^...] negative character class
258 [x-y] range (can be used for hex characters)
259 [[:xxx:]] positive POSIX named set
260 [[:^xxx:]] negative POSIX named set
266 cntrl control character
268 graph printing, excluding space
269 lower lower case letter
270 print printing, including space
271 punct printing, excluding alphanumeric
273 upper upper case letter
275 xdigit hexadecimal digit
277 In PCRE, POSIX character set names recognize only ASCII characters by default,
278 but some of them use Unicode properties if PCRE_UCP is set. You can use
279 \Q...\E inside a character class.
281 <br><a name="SEC9" href="#TOC1">QUANTIFIERS</a><br>
285 ?+ 0 or 1, possessive
288 *+ 0 or more, possessive
291 ++ 1 or more, possessive
294 {n,m} at least n, no more than m, greedy
295 {n,m}+ at least n, no more than m, possessive
296 {n,m}? at least n, no more than m, lazy
297 {n,} n or more, greedy
298 {n,}+ n or more, possessive
299 {n,}? n or more, lazy
302 <br><a name="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
306 \B not a word boundary
308 also after internal newline in multiline mode
311 also before newline at end of subject
312 also before internal newline in multiline mode
314 also before newline at end of subject
316 \G first matching position in subject
319 <br><a name="SEC11" href="#TOC1">MATCH POINT RESET</a><br>
322 \K reset start of match
325 <br><a name="SEC12" href="#TOC1">ALTERNATION</a><br>
331 <br><a name="SEC13" href="#TOC1">CAPTURING</a><br>
334 (...) capturing group
335 (?<name>...) named capturing group (Perl)
336 (?'name'...) named capturing group (Perl)
337 (?P<name>...) named capturing group (Python)
338 (?:...) non-capturing group
339 (?|...) non-capturing group; reset group numbers for
340 capturing groups in each alternative
343 <br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br>
346 (?>...) atomic, non-capturing group
349 <br><a name="SEC15" href="#TOC1">COMMENT</a><br>
352 (?#....) comment (not nestable)
355 <br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br>
359 (?J) allow duplicate names
361 (?s) single line (dotall)
362 (?U) default ungreedy (lazy)
363 (?x) extended (ignore white space)
364 (?-...) unset option(s)
366 The following are recognized only at the start of a pattern or after one of the
367 newline-setting options with similar syntax:
369 (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)
370 (*UTF8) set UTF-8 mode (PCRE_UTF8)
371 (*UCP) set PCRE_UCP (use Unicode properties for \d etc)
374 <br><a name="SEC17" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
377 (?=...) positive look ahead
378 (?!...) negative look ahead
379 (?<=...) positive look behind
380 (?<!...) negative look behind
382 Each top-level branch of a look behind must be of a fixed length.
384 <br><a name="SEC18" href="#TOC1">BACKREFERENCES</a><br>
387 \n reference by number (can be ambiguous)
388 \gn reference by number
389 \g{n} reference by number
390 \g{-n} relative reference by number
391 \k<name> reference by name (Perl)
392 \k'name' reference by name (Perl)
393 \g{name} reference by name (Perl)
394 \k{name} reference by name (.NET)
395 (?P=name) reference by name (Python)
398 <br><a name="SEC19" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
401 (?R) recurse whole pattern
402 (?n) call subpattern by absolute number
403 (?+n) call subpattern by relative number
404 (?-n) call subpattern by relative number
405 (?&name) call subpattern by name (Perl)
406 (?P>name) call subpattern by name (Python)
407 \g<name> call subpattern by name (Oniguruma)
408 \g'name' call subpattern by name (Oniguruma)
409 \g<n> call subpattern by absolute number (Oniguruma)
410 \g'n' call subpattern by absolute number (Oniguruma)
411 \g<+n> call subpattern by relative number (PCRE extension)
412 \g'+n' call subpattern by relative number (PCRE extension)
413 \g<-n> call subpattern by relative number (PCRE extension)
414 \g'-n' call subpattern by relative number (PCRE extension)
417 <br><a name="SEC20" href="#TOC1">CONDITIONAL PATTERNS</a><br>
420 (?(condition)yes-pattern)
421 (?(condition)yes-pattern|no-pattern)
423 (?(n)... absolute reference condition
424 (?(+n)... relative reference condition
425 (?(-n)... relative reference condition
426 (?(<name>)... named reference condition (Perl)
427 (?('name')... named reference condition (Perl)
428 (?(name)... named reference condition (PCRE)
429 (?(R)... overall recursion condition
430 (?(Rn)... specific group recursion condition
431 (?(R&name)... specific recursion condition
432 (?(DEFINE)... define subpattern for reference
433 (?(assert)... assertion condition
436 <br><a name="SEC21" href="#TOC1">BACKTRACKING CONTROL</a><br>
438 The following act immediately they are reached:
440 (*ACCEPT) force successful match
441 (*FAIL) force backtrack; synonym (*F)
443 The following act only when a subsequent match failure causes a backtrack to
444 reach them. They all force a match failure, but they differ in what happens
445 afterwards. Those that advance the start-of-match point do so only if the
446 pattern is not anchored.
448 (*COMMIT) overall failure, no advance of starting point
449 (*PRUNE) advance to next starting character
450 (*SKIP) advance start to current matching position
451 (*THEN) local failure, backtrack to next alternation
454 <br><a name="SEC22" href="#TOC1">NEWLINE CONVENTIONS</a><br>
456 These are recognized only at the very start of the pattern or after a
457 (*BSR_...) or (*UTF8) or (*UCP) option.
459 (*CR) carriage return only
461 (*CRLF) carriage return followed by linefeed
462 (*ANYCRLF) all three of the above
463 (*ANY) any Unicode newline sequence
466 <br><a name="SEC23" href="#TOC1">WHAT \R MATCHES</a><br>
468 These are recognized only at the very start of the pattern or after a
469 (*...) option that sets the newline convention or UTF-8 or UCP mode.
471 (*BSR_ANYCRLF) CR, LF, or CRLF
472 (*BSR_UNICODE) any Unicode newline sequence
475 <br><a name="SEC24" href="#TOC1">CALLOUTS</a><br>
479 (?Cn) callout with data n
482 <br><a name="SEC25" href="#TOC1">SEE ALSO</a><br>
484 <b>pcrepattern</b>(3), <b>pcreapi</b>(3), <b>pcrecallout</b>(3),
485 <b>pcrematching</b>(3), <b>pcre</b>(3).
487 <br><a name="SEC26" href="#TOC1">AUTHOR</a><br>
491 University Computing Service
493 Cambridge CB2 3QH, England.
496 <br><a name="SEC27" href="#TOC1">REVISION</a><br>
498 Last updated: 21 November 2010
500 Copyright © 1997-2010 University of Cambridge.
503 Return to the <a href="index.html">PCRE index page</a>.