NAME | PCRE REGULAR EXPRESSION SYNTAX SUMMARY | QUOTING | CHARACTERS | CHARACTER TYPES | GENERAL CATEGORY PROPERTIES FOR \p and \P | PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P | SCRIPT NAMES FOR \p AND \P | CHARACTER CLASSES | QUANTIFIERS | ANCHORS AND SIMPLE ASSERTIONS | MATCH POINT RESET | ALTERNATION | CAPTURING | ATOMIC GROUPS | COMMENT | OPTION SETTING | NEWLINE CONVENTION | WHAT \R MATCHES | LOOKAHEAD AND LOOKBEHIND ASSERTIONS | BACKREFERENCES | SUBROUTINE REFERENCES (POSSIBLY RECURSIVE) | CONDITIONAL PATTERNS | BACKTRACKING CONTROL | CALLOUTS | SEE ALSO | AUTHOR | REVISION | COLOPHON

PCRESYNTAX(3)             Library Functions Manual             PCRESYNTAX(3)

NAME         top

       PCRE - Perl-compatible regular expressions

PCRE REGULAR EXPRESSION SYNTAX SUMMARY         top


       The full syntax and semantics of the regular expressions that are
       supported by PCRE are described in the pcrepattern documentation.
       This document contains a quick-reference summary of the syntax.

QUOTING         top


         \x         where x is non-alphanumeric is a literal x
         \Q...\E    treat enclosed characters as literal

CHARACTERS         top


         \a         alarm, that is, the BEL character (hex 07)
         \cx        "control-x", where x is any ASCII character
         \e         escape (hex 1B)
         \f         form feed (hex 0C)
         \n         newline (hex 0A)
         \r         carriage return (hex 0D)
         \t         tab (hex 09)
         \0dd       character with octal code 0dd
         \ddd       character with octal code ddd, or backreference
         \o{ddd..}  character with octal code ddd..
         \xhh       character with hex code hh
         \x{hhh..}  character with hex code hhh..

       Note that \0dd is always an octal code, and that \8 and \9 are the
       literal characters "8" and "9".

CHARACTER TYPES         top


         .          any character except newline;
                      in dotall mode, any character whatsoever
         \C         one data unit, even in UTF mode (best avoided)
         \d         a decimal digit
         \D         a character that is not a decimal digit
         \h         a horizontal white space character
         \H         a character that is not a horizontal white space
       character
         \N         a character that is not a newline
         \p{xx}     a character with the xx property
         \P{xx}     a character without the xx property
         \R         a newline sequence
         \s         a white space character
         \S         a character that is not a white space character
         \v         a vertical white space character
         \V         a character that is not a vertical white space character
         \w         a "word" character
         \W         a "non-word" character
         \X         a Unicode extended grapheme cluster

       By default, \d, \s, and \w match only ASCII characters, even in UTF-8
       mode or in the 16- bit and 32-bit libraries. However, if locale-
       specific matching is happening, \s and \w may also match characters
       with code points in the range 128-255. If the PCRE_UCP option is set,
       the behaviour of these escape sequences is changed to use Unicode
       properties and they match many more characters.

GENERAL CATEGORY PROPERTIES FOR \p and \P         top


         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

PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P         top


         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, VT, FF, CR
         Xuc        Univerally-named character: one that can be
                      represented by a Universal Character Name
         Xwd        Perl word: property Xan or underscore

       Perl and POSIX space are now the same. Perl added VT to its space
       character set at release 5.18 and PCRE changed at release 8.34.

SCRIPT NAMES FOR \p AND \P         top


       Arabic, Armenian, Avestan, Balinese, Bamum, Bassa_Vah, Batak,
       Bengali, Bopomofo, Brahmi, Braille, Buginese, Buhid,
       Canadian_Aboriginal, Carian, Caucasian_Albanian, Chakma, Cham,
       Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret,
       Devanagari, Duployan, Egyptian_Hieroglyphs, Elbasan, Ethiopic,
       Georgian, Glagolitic, Gothic, Grantha, Greek, Gujarati, Gurmukhi,
       Han, Hangul, Hanunoo, Hebrew, Hiragana, Imperial_Aramaic, Inherited,
       Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi,
       Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Khojki, Khudawadi,
       Lao, Latin, Lepcha, Limbu, Linear_A, Linear_B, Lisu, Lycian, Lydian,
       Mahajani, Malayalam, Mandaic, Manichaean, Meetei_Mayek,
       Mende_Kikakui, Meroitic_Cursive, Meroitic_Hieroglyphs, Miao, Modi,
       Mongolian, Mro, Myanmar, Nabataean, New_Tai_Lue, Nko, Ogham,
       Ol_Chiki, Old_Italic, Old_North_Arabian, Old_Permic, Old_Persian,
       Old_South_Arabian, Old_Turkic, Oriya, Osmanya, Pahawh_Hmong,
       Palmyrene, Pau_Cin_Hau, Phags_Pa, Phoenician, Psalter_Pahlavi,
       Rejang, Runic, Samaritan, Saurashtra, Sharada, Shavian, Siddham,
       Sinhala, Sora_Sompeng, Sundanese, Syloti_Nagri, Syriac, Tagalog,
       Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, Takri, Tamil, Telugu, Thaana,
       Thai, Tibetan, Tifinagh, Tirhuta, Ugaritic, Vai, Warang_Citi, Yi.

CHARACTER CLASSES         top


         [...]       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       white space
         upper       upper case letter
         word        same as \w
         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 \Q...\E inside a character class.

QUANTIFIERS         top


         ?           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

ANCHORS AND SIMPLE ASSERTIONS         top


         \b          word boundary
         \B          not a word boundary
         ^           start of subject
                      also after internal newline in multiline mode
         \A          start of subject
         $           end of subject
                      also before newline at end of subject
                      also before internal newline in multiline mode
         \Z          end of subject
                      also before newline at end of subject
         \z          end of subject
         \G          first matching position in subject

MATCH POINT RESET         top


         \K          reset start of match

       \K is honoured in positive assertions, but ignored in negative ones.

ALTERNATION         top


         expr|expr|expr...

CAPTURING         top


         (...)           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

ATOMIC GROUPS         top


         (?>...)         atomic, non-capturing group

COMMENT         top


         (?#....)        comment (not nestable)

OPTION SETTING         top


         (?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 very start of a pattern or
       after one of the newline or \R options with similar syntax. More than
       one of them may appear.

         (*LIMIT_MATCH=d) set the match limit to d (decimal number)
         (*LIMIT_RECURSION=d) set the recursion limit to d (decimal number)
         (*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS)
         (*NO_START_OPT) no start-match optimization
       (PCRE_NO_START_OPTIMIZE)
         (*UTF8)         set UTF-8 mode: 8-bit library (PCRE_UTF8)
         (*UTF16)        set UTF-16 mode: 16-bit library (PCRE_UTF16)
         (*UTF32)        set UTF-32 mode: 32-bit library (PCRE_UTF32)
         (*UTF)          set appropriate UTF mode for the library in use
         (*UCP)          set PCRE_UCP (use Unicode properties for \d etc)

       Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value
       of the limits set by the caller of pcre_exec(), not increase them.

NEWLINE CONVENTION         top


       These are recognized only at the very start of the pattern or after
       option settings with a similar syntax.

         (*CR)           carriage return only
         (*LF)           linefeed only
         (*CRLF)         carriage return followed by linefeed
         (*ANYCRLF)      all three of the above
         (*ANY)          any Unicode newline sequence

WHAT \R MATCHES         top


       These are recognized only at the very start of the pattern or after
       option setting with a similar syntax.

         (*BSR_ANYCRLF)  CR, LF, or CRLF
         (*BSR_UNICODE)  any Unicode newline sequence

LOOKAHEAD AND LOOKBEHIND ASSERTIONS         top


         (?=...)         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.

BACKREFERENCES         top


         \n              reference by number (can be ambiguous)
         \gn             reference by number
         \g{n}           reference by number
         \g{-n}          relative reference by number
         \k<name>        reference by name (Perl)
         \k'name'        reference by name (Perl)
         \g{name}        reference by name (Perl)
         \k{name}        reference by name (.NET)
         (?P=name)       reference by name (Python)

SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)         top


         (?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)
         \g<name>        call subpattern by name (Oniguruma)
         \g'name'        call subpattern by name (Oniguruma)
         \g<n>           call subpattern by absolute number (Oniguruma)
         \g'n'           call subpattern by absolute number (Oniguruma)
         \g<+n>          call subpattern by relative number (PCRE extension)
         \g'+n'          call subpattern by relative number (PCRE extension)
         \g<-n>          call subpattern by relative number (PCRE extension)
         \g'-n'          call subpattern by relative number (PCRE extension)

CONDITIONAL PATTERNS         top


         (?(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

BACKTRACKING CONTROL         top


       The following act immediately they are reached:

         (*ACCEPT)       force successful match
         (*FAIL)         force backtrack; synonym (*F)
         (*MARK:NAME)    set name to be passed back; synonym (*:NAME)

       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
         (*PRUNE:NAME)   equivalent to (*MARK:NAME)(*PRUNE)
         (*SKIP)         advance to current matching position
         (*SKIP:NAME)    advance to position corresponding to an earlier
                         (*MARK:NAME); if not found, the (*SKIP) is ignored
         (*THEN)         local failure, backtrack to next alternation
         (*THEN:NAME)    equivalent to (*MARK:NAME)(*THEN)

CALLOUTS         top


         (?C)      callout
         (?Cn)     callout with data n

SEE ALSO         top


       pcrepattern(3), pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).

AUTHOR         top


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

REVISION         top


       Last updated: 08 January 2014
       Copyright (c) 1997-2014 University of Cambridge.

COLOPHON         top

       This page is part of the PCRE (Perl Compatible Regular Expressions)
       project.  Information about the project can be found at 
       ⟨http://www.pcre.org/⟩.  If you have a bug report for this manual
       page, see ⟨http://bugs.exim.org/enter_bug.cgi?product=PCRE⟩.  This
       page was obtained from the tarball pcre-8.40.tar.gz fetched from 
       ⟨ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/⟩ on
       2017-04-25.  If you discover any rendering problems in this HTML ver‐
       sion of the page, or you believe there is a better or more up-to-date
       source for the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original man‐
       ual page), send a mail to man-pages@man7.org

PCRE 8.35                      08 January 2014                 PCRESYNTAX(3)

Pages that refer to this page: pcregrep(1)pcrepattern(3)