OpenGrok

PCRE - Perl-compatible regular expressions .rs The full syntax and semantics of the regular expressions that are supported by PCRE are described in the HREF
pcrepattern
documentation. This document contains just a quick-reference summary of the syntax. . . .rs \ex where x is non-alphanumeric is a literal x \eQ...\eE treat enclosed characters as literal . . .rs \ea alarm, that is, the BEL character (hex 07) \ecx "control-x", where x is any ASCII character \ee escape (hex 1B) \ef formfeed (hex 0C) \en newline (hex 0A) \er carriage return (hex 0D) \et tab (hex 09) \eddd character with octal code ddd, or backreference \exhh character with hex code hh \ex{hhh..} character with hex code hhh.. . . .rs . any character except newline; in dotall mode, any character whatsoever \eC one byte, even in UTF-8 mode (best avoided) \ed a decimal digit \eD a character that is not a decimal digit \eh a horizontal whitespace character \eH a character that is not a horizontal whitespace character \eN a character that is not a newline \ep{xx} a character with the xx property \eP{xx} a character without the xx property \eR a newline sequence \es a whitespace character \eS a character that is not a whitespace character \ev a vertical whitespace character \eV a character that is not a vertical whitespace character \ew a "word" character \eW a "non-word" character \eX an extended Unicode sequence In PCRE, by default, \ed, \eD, \es, \eS, \ew, and \eW recognize only ASCII characters, even in UTF-8 mode. However, this can be changed by setting the PCRE_UCP option. . . .rs C Other Cc Control Cf Format Cn Unassigned Co Private use Cs Surrogate L Letter Ll Lower case letter Lm Modifier letter Lo Other letter Lt Title case letter Lu Upper case letter L& Ll, Lu, or Lt M Mark Mc Spacing mark Me Enclosing mark Mn Non-spacing mark N Number Nd Decimal number Nl Letter number No Other number P Punctuation Pc Connector punctuation Pd Dash punctuation Pe Close punctuation Pf Final punctuation Pi Initial punctuation Po Other punctuation Ps Open punctuation S Symbol Sc Currency symbol Sk Modifier symbol Sm Mathematical symbol So Other symbol Z Separator Zl Line separator Zp Paragraph separator Zs Space separator . . .rs Xan Alphanumeric: union of properties L and N Xps POSIX space: property Z or tab, NL, VT, FF, CR Xsp Perl space: property Z or tab, NL, FF, CR Xwd Perl word: property Xan or underscore . . .rs Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam, Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samaritan, Saurashtra, Shavian, Sinhala, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, Yi. . . .rs [...] positive character class [^...] negative character class [x-y] range (can be used for hex characters) [[:xxx:]] positive POSIX named set [[:^xxx:]] negative POSIX named set alnum alphanumeric alpha alphabetic ascii 0-127 blank space or tab cntrl control character digit decimal digit graph printing, excluding space lower lower case letter print printing, including space punct printing, excluding alphanumeric space whitespace upper upper case letter word same as \ew xdigit hexadecimal digit In PCRE, POSIX character set names recognize only ASCII characters by default, but some of them use Unicode properties if PCRE_UCP is set. You can use \eQ...\eE inside a character class. . . .rs ? 0 or 1, greedy ?+ 0 or 1, possessive ?? 0 or 1, lazy * 0 or more, greedy *+ 0 or more, possessive *? 0 or more, lazy + 1 or more, greedy ++ 1 or more, possessive +? 1 or more, lazy {n} exactly n {n,m} at least n, no more than m, greedy {n,m}+ at least n, no more than m, possessive {n,m}? at least n, no more than m, lazy {n,} n or more, greedy {n,}+ n or more, possessive {n,}? n or more, lazy . . .rs \eb word boundary \eB not a word boundary ^ start of subject also after internal newline in multiline mode \eA start of subject $ end of subject also before newline at end of subject also before internal newline in multiline mode \eZ end of subject also before newline at end of subject \ez end of subject \eG first matching position in subject . . .rs \eK reset start of match . . .rs expr|expr|expr... . . .rs (...) capturing group (?<name>...) named capturing group (Perl) (?'name'...) named capturing group (Perl) (?P<name>...) named capturing group (Python) (?:...) non-capturing group (?|...) non-capturing group; reset group numbers for capturing groups in each alternative . . .rs (?>...) atomic, non-capturing group . . . . .rs (?#....) comment (not nestable) . . .rs (?i) caseless (?J) allow duplicate names (?m) multiline (?s) single line (dotall) (?U) default ungreedy (lazy) (?x) extended (ignore white space) (?-...) unset option(s) The following are recognized only at the start of a pattern or after one of the newline-setting options with similar syntax: (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE) (*UTF8) set UTF-8 mode (PCRE_UTF8) (*UCP) set PCRE_UCP (use Unicode properties for \ed etc) . . .rs (?=...) positive look ahead (?!...) negative look ahead (?<=...) positive look behind (?<!...) negative look behind Each top-level branch of a look behind must be of a fixed length. . . .rs \en reference by number (can be ambiguous) \egn reference by number \eg{n} reference by number \eg{-n} relative reference by number \ek<name> reference by name (Perl) \ek'name' reference by name (Perl) \eg{name} reference by name (Perl) \ek{name} reference by name (.NET) (?P=name) reference by name (Python) . . .rs (?R) recurse whole pattern (?n) call subpattern by absolute number (?+n) call subpattern by relative number (?-n) call subpattern by relative number (?&name) call subpattern by name (Perl) (?P>name) call subpattern by name (Python) \eg<name> call subpattern by name (Oniguruma) \eg'name' call subpattern by name (Oniguruma) \eg<n> call subpattern by absolute number (Oniguruma) \eg'n' call subpattern by absolute number (Oniguruma) \eg<+n> call subpattern by relative number (PCRE extension) \eg'+n' call subpattern by relative number (PCRE extension) \eg<-n> call subpattern by relative number (PCRE extension) \eg'-n' call subpattern by relative number (PCRE extension) . . .rs (?(condition)yes-pattern) (?(condition)yes-pattern|no-pattern) (?(n)... absolute reference condition (?(+n)... relative reference condition (?(-n)... relative reference condition (?(<name>)... named reference condition (Perl) (?('name')... named reference condition (Perl) (?(name)... named reference condition (PCRE) (?(R)... overall recursion condition (?(Rn)... specific group recursion condition (?(R&name)... specific recursion condition (?(DEFINE)... define subpattern for reference (?(assert)... assertion condition . . .rs The following act immediately they are reached: (*ACCEPT) force successful match (*FAIL) force backtrack; synonym (*F) The following act only when a subsequent match failure causes a backtrack to reach them. They all force a match failure, but they differ in what happens afterwards. Those that advance the start-of-match point do so only if the pattern is not anchored. (*COMMIT) overall failure, no advance of starting point (*PRUNE) advance to next starting character (*SKIP) advance start to current matching position (*THEN) local failure, backtrack to next alternation . . .rs These are recognized only at the very start of the pattern or after a (*BSR_...) or (*UTF8) or (*UCP) option. (*CR) carriage return only (*LF) linefeed only (*CRLF) carriage return followed by linefeed (*ANYCRLF) all three of the above (*ANY) any Unicode newline sequence . . .rs These are recognized only at the very start of the pattern or after a (*...) option that sets the newline convention or UTF-8 or UCP mode. (*BSR_ANYCRLF) CR, LF, or CRLF (*BSR_UNICODE) any Unicode newline sequence . . .rs (?C) callout (?Cn) callout with data n . . .rs pcrepattern(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3). . . .rs

Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.

. . .rs

Last updated: 21 November 2010
Copyright (c) 1997-2010 University of Cambridge.