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PCRESYNTAX(3)		   Library Functions Manual		 PCRESYNTAX(3)

NAME
       PCRE - Perl-compatible regular expressions

PCRE REGULAR EXPRESSION	SYNTAX SUMMARY
       The  full syntax	and semantics of the regular expressions that are sup-
       ported by PCRE are described in	the  pcrepattern  documentation.  This
       document	contains a quick-reference summary of the syntax.

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

CHARACTERS
	 \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 lit-
       eral characters "8" and "9".

CHARACTER TYPES
	 .	    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-spe-
       cific 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  proper-
       ties and	they match many	more characters.

GENERAL	CATEGORY PROPERTIES FOR	\p and \P
	 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
	 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 char-
       acter set at release 5.18 and PCRE changed at release 8.34.

SCRIPT NAMES FOR \p AND	\P
       Arabic, Armenian, Avestan, Balinese, Bamum, Bassa_Vah, Batak,  Bengali,
       Bopomofo,  Brahmi,  Braille, Buginese, Buhid, Canadian_Aboriginal, Car-
       ian, Caucasian_Albanian,	Chakma,	Cham, Cherokee,	Common,	Coptic,	Cunei-
       form, Cypriot, Cyrillic,	Deseret, Devanagari, Duployan, Egyptian_Hiero-
       glyphs,	Elbasan,  Ethiopic,  Georgian,	Glagolitic,  Gothic,  Grantha,
       Greek,  Gujarati, Gurmukhi, Han,	Hangul,	Hanunoo, Hebrew, Hiragana, Im-
       perial_Aramaic,	   Inherited,	  Inscriptional_Pahlavi,      Inscrip-
       tional_Parthian,	  Javanese,   Kaithi,	Kannada,  Katakana,  Kayah_Li,
       Kharoshthi, Khmer, Khojki, Khudawadi, Lao, Latin, Lepcha,  Limbu,  Lin-
       ear_A,  Linear_B,  Lisu,	 Lycian, Lydian, Mahajani, Malayalam, Mandaic,
       Manichaean, Meetei_Mayek, Mende_Kikakui,	Meroitic_Cursive, Meroitic_Hi-
       eroglyphs, 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,  Pa-
       hawh_Hmong,    Palmyrene,    Pau_Cin_Hau,     Phags_Pa,	   Phoenician,
       Psalter_Pahlavi,	 Rejang,  Runic,  Samaritan, Saurashtra, Sharada, Sha-
       vian, 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
	 [...]	     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
	 ?	     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
	 \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
	 \K	     reset start of match

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

ALTERNATION
	 expr|expr|expr...

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

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

OPTION SETTING
	 (?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 af-
       ter 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
       These are recognized only at the	very start of the pattern or after op-
       tion 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
       These are recognized only at the	very start of the pattern or after op-
       tion setting with a similar syntax.

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

LOOKAHEAD AND LOOKBEHIND ASSERTIONS
	 (?=...)	 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
	 \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)
	 (?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
	 (?(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
       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	 back-
       track 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
	 (?C)	   callout
	 (?Cn)	   callout with	data n

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

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

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

PCRE 8.35			08 January 2014			 PCRESYNTAX(3)

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

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