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">NEWLINE CONVENTION</a>
33 <li><a name="TOC18" href="#SEC18">WHAT \R MATCHES</a>
34 <li><a name="TOC19" href="#SEC19">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
35 <li><a name="TOC20" href="#SEC20">BACKREFERENCES</a>
36 <li><a name="TOC21" href="#SEC21">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
37 <li><a name="TOC22" href="#SEC22">CONDITIONAL PATTERNS</a>
38 <li><a name="TOC23" href="#SEC23">BACKTRACKING CONTROL</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 a quick-reference summary of the syntax.
51 <br><a name="SEC2" href="#TOC1">QUOTING</a><br>
54 \x where x is non-alphanumeric is a literal x
55 \Q...\E treat enclosed characters as literal
58 <br><a name="SEC3" href="#TOC1">CHARACTERS</a><br>
61 \a alarm, that is, the BEL character (hex 07)
62 \cx "control-x", where x is any ASCII character
66 \r carriage return (hex 0D)
68 \0dd character with octal code 0dd
69 \ddd character with octal code ddd, or backreference
70 \o{ddd..} character with octal code ddd..
71 \xhh character with hex code hh
72 \x{hhh..} character with hex code hhh..
74 Note that \0dd is always an octal code, and that \8 and \9 are the literal
75 characters "8" and "9".
77 <br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br>
80 . any character except newline;
81 in dotall mode, any character whatsoever
82 \C one data unit, even in UTF mode (best avoided)
84 \D a character that is not a decimal digit
85 \h a horizontal white space character
86 \H a character that is not a horizontal white space character
87 \N a character that is not a newline
88 \p{<i>xx</i>} a character with the <i>xx</i> property
89 \P{<i>xx</i>} a character without the <i>xx</i> property
91 \s a white space character
92 \S a character that is not a white space character
93 \v a vertical white space character
94 \V a character that is not a vertical white space character
96 \W a "non-word" character
97 \X a Unicode extended grapheme cluster
99 By default, \d, \s, and \w match only ASCII characters, even in UTF-8 mode
100 or in the 16- bit and 32-bit libraries. However, if locale-specific matching is
101 happening, \s and \w may also match characters with code points in the range
102 128-255. If the PCRE_UCP option is set, the behaviour of these escape sequences
103 is changed to use Unicode properties and they match many more characters.
105 <br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a><br>
134 Pc Connector punctuation
138 Pi Initial punctuation
145 Sm Mathematical symbol
150 Zp Paragraph separator
154 <br><a name="SEC6" href="#TOC1">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br>
157 Xan Alphanumeric: union of properties L and N
158 Xps POSIX space: property Z or tab, NL, VT, FF, CR
159 Xsp Perl space: property Z or tab, NL, VT, FF, CR
160 Xuc Univerally-named character: one that can be
161 represented by a Universal Character Name
162 Xwd Perl word: property Xan or underscore
164 Perl and POSIX space are now the same. Perl added VT to its space character set
165 at release 5.18 and PCRE changed at release 8.34.
167 <br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
196 Egyptian_Hieroglyphs,
213 Inscriptional_Pahlavi,
214 Inscriptional_Parthian,
240 Meroitic_Hieroglyphs,
295 <br><a name="SEC8" href="#TOC1">CHARACTER CLASSES</a><br>
298 [...] positive character class
299 [^...] negative character class
300 [x-y] range (can be used for hex characters)
301 [[:xxx:]] positive POSIX named set
302 [[:^xxx:]] negative POSIX named set
308 cntrl control character
310 graph printing, excluding space
311 lower lower case letter
312 print printing, including space
313 punct printing, excluding alphanumeric
315 upper upper case letter
317 xdigit hexadecimal digit
319 In PCRE, POSIX character set names recognize only ASCII characters by default,
320 but some of them use Unicode properties if PCRE_UCP is set. You can use
321 \Q...\E inside a character class.
323 <br><a name="SEC9" href="#TOC1">QUANTIFIERS</a><br>
327 ?+ 0 or 1, possessive
330 *+ 0 or more, possessive
333 ++ 1 or more, possessive
336 {n,m} at least n, no more than m, greedy
337 {n,m}+ at least n, no more than m, possessive
338 {n,m}? at least n, no more than m, lazy
339 {n,} n or more, greedy
340 {n,}+ n or more, possessive
341 {n,}? n or more, lazy
344 <br><a name="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
348 \B not a word boundary
350 also after internal newline in multiline mode
353 also before newline at end of subject
354 also before internal newline in multiline mode
356 also before newline at end of subject
358 \G first matching position in subject
361 <br><a name="SEC11" href="#TOC1">MATCH POINT RESET</a><br>
364 \K reset start of match
366 \K is honoured in positive assertions, but ignored in negative ones.
368 <br><a name="SEC12" href="#TOC1">ALTERNATION</a><br>
374 <br><a name="SEC13" href="#TOC1">CAPTURING</a><br>
377 (...) capturing group
378 (?<name>...) named capturing group (Perl)
379 (?'name'...) named capturing group (Perl)
380 (?P<name>...) named capturing group (Python)
381 (?:...) non-capturing group
382 (?|...) non-capturing group; reset group numbers for
383 capturing groups in each alternative
386 <br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br>
389 (?>...) atomic, non-capturing group
392 <br><a name="SEC15" href="#TOC1">COMMENT</a><br>
395 (?#....) comment (not nestable)
398 <br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br>
402 (?J) allow duplicate names
404 (?s) single line (dotall)
405 (?U) default ungreedy (lazy)
406 (?x) extended (ignore white space)
407 (?-...) unset option(s)
409 The following are recognized only at the very start of a pattern or after one
410 of the newline or \R options with similar syntax. More than one of them may
413 (*LIMIT_MATCH=d) set the match limit to d (decimal number)
414 (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number)
415 (*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS)
416 (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)
417 (*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8)
418 (*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16)
419 (*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32)
420 (*UTF) set appropriate UTF mode for the library in use
421 (*UCP) set PCRE_UCP (use Unicode properties for \d etc)
423 Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the
424 limits set by the caller of pcre_exec(), not increase them.
426 <br><a name="SEC17" href="#TOC1">NEWLINE CONVENTION</a><br>
428 These are recognized only at the very start of the pattern or after option
429 settings with a similar syntax.
431 (*CR) carriage return only
433 (*CRLF) carriage return followed by linefeed
434 (*ANYCRLF) all three of the above
435 (*ANY) any Unicode newline sequence
438 <br><a name="SEC18" href="#TOC1">WHAT \R MATCHES</a><br>
440 These are recognized only at the very start of the pattern or after option
441 setting with a similar syntax.
443 (*BSR_ANYCRLF) CR, LF, or CRLF
444 (*BSR_UNICODE) any Unicode newline sequence
447 <br><a name="SEC19" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
450 (?=...) positive look ahead
451 (?!...) negative look ahead
452 (?<=...) positive look behind
453 (?<!...) negative look behind
455 Each top-level branch of a look behind must be of a fixed length.
457 <br><a name="SEC20" href="#TOC1">BACKREFERENCES</a><br>
460 \n reference by number (can be ambiguous)
461 \gn reference by number
462 \g{n} reference by number
463 \g{-n} relative reference by number
464 \k<name> reference by name (Perl)
465 \k'name' reference by name (Perl)
466 \g{name} reference by name (Perl)
467 \k{name} reference by name (.NET)
468 (?P=name) reference by name (Python)
471 <br><a name="SEC21" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
474 (?R) recurse whole pattern
475 (?n) call subpattern by absolute number
476 (?+n) call subpattern by relative number
477 (?-n) call subpattern by relative number
478 (?&name) call subpattern by name (Perl)
479 (?P>name) call subpattern by name (Python)
480 \g<name> call subpattern by name (Oniguruma)
481 \g'name' call subpattern by name (Oniguruma)
482 \g<n> call subpattern by absolute number (Oniguruma)
483 \g'n' call subpattern by absolute number (Oniguruma)
484 \g<+n> call subpattern by relative number (PCRE extension)
485 \g'+n' call subpattern by relative number (PCRE extension)
486 \g<-n> call subpattern by relative number (PCRE extension)
487 \g'-n' call subpattern by relative number (PCRE extension)
490 <br><a name="SEC22" href="#TOC1">CONDITIONAL PATTERNS</a><br>
493 (?(condition)yes-pattern)
494 (?(condition)yes-pattern|no-pattern)
496 (?(n)... absolute reference condition
497 (?(+n)... relative reference condition
498 (?(-n)... relative reference condition
499 (?(<name>)... named reference condition (Perl)
500 (?('name')... named reference condition (Perl)
501 (?(name)... named reference condition (PCRE)
502 (?(R)... overall recursion condition
503 (?(Rn)... specific group recursion condition
504 (?(R&name)... specific recursion condition
505 (?(DEFINE)... define subpattern for reference
506 (?(assert)... assertion condition
509 <br><a name="SEC23" href="#TOC1">BACKTRACKING CONTROL</a><br>
511 The following act immediately they are reached:
513 (*ACCEPT) force successful match
514 (*FAIL) force backtrack; synonym (*F)
515 (*MARK:NAME) set name to be passed back; synonym (*:NAME)
517 The following act only when a subsequent match failure causes a backtrack to
518 reach them. They all force a match failure, but they differ in what happens
519 afterwards. Those that advance the start-of-match point do so only if the
520 pattern is not anchored.
522 (*COMMIT) overall failure, no advance of starting point
523 (*PRUNE) advance to next starting character
524 (*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE)
525 (*SKIP) advance to current matching position
526 (*SKIP:NAME) advance to position corresponding to an earlier
527 (*MARK:NAME); if not found, the (*SKIP) is ignored
528 (*THEN) local failure, backtrack to next alternation
529 (*THEN:NAME) equivalent to (*MARK:NAME)(*THEN)
532 <br><a name="SEC24" href="#TOC1">CALLOUTS</a><br>
536 (?Cn) callout with data n
539 <br><a name="SEC25" href="#TOC1">SEE ALSO</a><br>
541 <b>pcrepattern</b>(3), <b>pcreapi</b>(3), <b>pcrecallout</b>(3),
542 <b>pcrematching</b>(3), <b>pcre</b>(3).
544 <br><a name="SEC26" href="#TOC1">AUTHOR</a><br>
548 University Computing Service
550 Cambridge CB2 3QH, England.
553 <br><a name="SEC27" href="#TOC1">REVISION</a><br>
555 Last updated: 08 January 2014
557 Copyright © 1997-2014 University of Cambridge.
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