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<title>pcresyntax specification</title>
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<h1>pcresyntax man page</h1>

Return to the <a href="index.html">PCRE index page</a>.


This page is part of the PCRE HTML documentation. It was generated automatically
from the original man page. If there is any nonsense in it, please consult the
man page, in case the conversion went wrong.
 
<ul>
<li><a name="TOC1" href="#SEC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a>
<li><a name="TOC2" href="#SEC2">QUOTING</a>
<li><a name="TOC3" href="#SEC3">CHARACTERS</a>
<li><a name="TOC4" href="#SEC4">CHARACTER TYPES</a>
<li><a name="TOC5" href="#SEC5">GENERAL CATEGORY PROPERTIES FOR \p and \P</a>
<li><a name="TOC6" href="#SEC6">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a>
<li><a name="TOC7" href="#SEC7">SCRIPT NAMES FOR \p AND \P</a>
<li><a name="TOC8" href="#SEC8">CHARACTER CLASSES</a>
<li><a name="TOC9" href="#SEC9">QUANTIFIERS</a>
<li><a name="TOC10" href="#SEC10">ANCHORS AND SIMPLE ASSERTIONS</a>
<li><a name="TOC11" href="#SEC11">MATCH POINT RESET</a>
<li><a name="TOC12" href="#SEC12">ALTERNATION</a>
<li><a name="TOC13" href="#SEC13">CAPTURING</a>
<li><a name="TOC14" href="#SEC14">ATOMIC GROUPS</a>
<li><a name="TOC15" href="#SEC15">COMMENT</a>
<li><a name="TOC16" href="#SEC16">OPTION SETTING</a>
<li><a name="TOC17" href="#SEC17">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
<li><a name="TOC18" href="#SEC18">BACKREFERENCES</a>
<li><a name="TOC19" href="#SEC19">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
<li><a name="TOC20" href="#SEC20">CONDITIONAL PATTERNS</a>
<li><a name="TOC21" href="#SEC21">BACKTRACKING CONTROL</a>
<li><a name="TOC22" href="#SEC22">NEWLINE CONVENTIONS</a>
<li><a name="TOC23" href="#SEC23">WHAT \R MATCHES</a>
<li><a name="TOC24" href="#SEC24">CALLOUTS</a>
<li><a name="TOC25" href="#SEC25">SEE ALSO</a>
<li><a name="TOC26" href="#SEC26">AUTHOR</a>
<li><a name="TOC27" href="#SEC27">REVISION</a>
</ul>
 <a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a> 

The full syntax and semantics of the regular expressions that are supported by
PCRE are described in the
<a href="pcrepattern.html">pcrepattern</a>
documentation. This document contains a quick-reference summary of the syntax.

 <a name="SEC2" href="#TOC1">QUOTING</a> 

<pre>
 \x where x is non-alphanumeric is a literal x
 \Q...\E treat enclosed characters as literal
</PRE>

 <a name="SEC3" href="#TOC1">CHARACTERS</a> 

<pre>
 \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)
 \ddd character with octal code ddd, or backreference
 \xhh character with hex code hh
 \x{hhh..} character with hex code hhh..
</PRE>

 <a name="SEC4" href="#TOC1">CHARACTER TYPES</a> 

<pre>
 . 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
</pre>
In PCRE, by default, \d, \D, \s, \S, \w, and \W recognize only ASCII
characters, even in a UTF mode. However, this can be changed by setting the
PCRE_UCP option.

 <a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a> 

<pre>
 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
</PRE>

 <a name="SEC6" href="#TOC1">PCRE SPECIAL CATEGORY PROPERTIES FOR \p and \P</a> 

<pre>
 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
</PRE>

 <a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a> 

Arabic,
Armenian,
Avestan,
Balinese,
Bamum,
Batak,
Bengali,
Bopomofo,
Brahmi,
Braille,
Buginese,
Buhid,
Canadian_Aboriginal,
Carian,
Chakma,
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,
Mandaic,
Meetei_Mayek,
Meroitic_Cursive,
Meroitic_Hieroglyphs,
Miao,
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,
Sharada,
Shavian,
Sinhala,
Sora_Sompeng,
Sundanese,
Syloti_Nagri,
Syriac,
Tagalog,
Tagbanwa,
Tai_Le,
Tai_Tham,
Tai_Viet,
Takri,
Tamil,
Telugu,
Thaana,
Thai,
Tibetan,
Tifinagh,
Ugaritic,
Vai,
Yi.

 <a name="SEC8" href="#TOC1">CHARACTER CLASSES</a> 

<pre>
 [...] 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
</pre>
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.

 <a name="SEC9" href="#TOC1">QUANTIFIERS</a> 

<pre>
 ? 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
</PRE>

 <a name="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a> 

<pre>
 \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
</PRE>

 <a name="SEC11" href="#TOC1">MATCH POINT RESET</a> 

<pre>
 \K reset start of match
</PRE>

 <a name="SEC12" href="#TOC1">ALTERNATION</a> 

<pre>
 expr|expr|expr...
</PRE>

 <a name="SEC13" href="#TOC1">CAPTURING</a> 

<pre>
 (...) capturing group
 (?&#60;name&#62;...) named capturing group (Perl)
 (?'name'...) named capturing group (Perl)
 (?P&#60;name&#62;...) named capturing group (Python)
 (?:...) non-capturing group
 (?|...) non-capturing group; reset group numbers for
 capturing groups in each alternative
</PRE>

 <a name="SEC14" href="#TOC1">ATOMIC GROUPS</a> 

<pre>
 (?&#62;...) atomic, non-capturing group
</PRE>

 <a name="SEC15" href="#TOC1">COMMENT</a> 

<pre>
 (?#....) comment (not nestable)
</PRE>

 <a name="SEC16" href="#TOC1">OPTION SETTING</a> 

<pre>
 (?i) caseless
 (?J) allow duplicate names
 (?m) multiline
 (?s) single line (dotall)
 (?U) default ungreedy (lazy)
 (?x) extended (ignore white space)
 (?-...) unset option(s)
</pre>
The following are recognized only at the start of a pattern or after one of the
newline-setting options with similar syntax:
<pre>
 (*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)
</PRE>

 <a name="SEC17" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a> 

<pre>
 (?=...) positive look ahead
 (?!...) negative look ahead
 (?&#60;=...) positive look behind
 (?&#60;!...) negative look behind
</pre>
Each top-level branch of a look behind must be of a fixed length.

 <a name="SEC18" href="#TOC1">BACKREFERENCES</a> 

<pre>
 \n reference by number (can be ambiguous)
 \gn reference by number
 \g{n} reference by number
 \g{-n} relative reference by number
 \k&#60;name&#62; 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)
</PRE>

 <a name="SEC19" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a> 

<pre>
 (?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&#62;name) call subpattern by name (Python)
 \g&#60;name&#62; call subpattern by name (Oniguruma)
 \g'name' call subpattern by name (Oniguruma)
 \g&#60;n&#62; call subpattern by absolute number (Oniguruma)
 \g'n' call subpattern by absolute number (Oniguruma)
 \g&#60;+n&#62; call subpattern by relative number (PCRE extension)
 \g'+n' call subpattern by relative number (PCRE extension)
 \g&#60;-n&#62; call subpattern by relative number (PCRE extension)
 \g'-n' call subpattern by relative number (PCRE extension)
</PRE>

 <a name="SEC20" href="#TOC1">CONDITIONAL PATTERNS</a> 

<pre>
 (?(condition)yes-pattern)
 (?(condition)yes-pattern|no-pattern)

(?(n)... absolute reference condition
 (?(+n)... relative reference condition
 (?(-n)... relative reference condition
 (?(&#60;name&#62;)... 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
</PRE>

 <a name="SEC21" href="#TOC1">BACKTRACKING CONTROL</a> 

The following act immediately they are reached:
<pre>
 (*ACCEPT) force successful match
 (*FAIL) force backtrack; synonym (*F)
 (*MARK:NAME) set name to be passed back; synonym (*:NAME)
</pre>
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.
<pre>
 (*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)
</PRE>

 <a name="SEC22" href="#TOC1">NEWLINE CONVENTIONS</a> 

These are recognized only at the very start of the pattern or after a
(*BSR_...), (*UTF8), (*UTF16), (*UTF32) or (*UCP) option.
<pre>
 (*CR) carriage return only
 (*LF) linefeed only
 (*CRLF) carriage return followed by linefeed
 (*ANYCRLF) all three of the above
 (*ANY) any Unicode newline sequence
</PRE>

 <a name="SEC23" href="#TOC1">WHAT \R MATCHES</a> 

These are recognized only at the very start of the pattern or after a
(*...) option that sets the newline convention or a UTF or UCP mode.
<pre>
 (*BSR_ANYCRLF) CR, LF, or CRLF
 (*BSR_UNICODE) any Unicode newline sequence
</PRE>

 <a name="SEC24" href="#TOC1">CALLOUTS</a> 

<pre>
 (?C) callout
 (?Cn) callout with data n
</PRE>

 <a name="SEC25" href="#TOC1">SEE ALSO</a> 

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

 <a name="SEC26" href="#TOC1">AUTHOR</a> 

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

 <a name="SEC27" href="#TOC1">REVISION</a> 

Last updated: 11 November 2012
 
Copyright &copy; 1997-2012 University of Cambridge.
 

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