doc/html/pcresyntax.html

<html>
<head>
<title>pcresyntax specification</title>
</head>
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
<h1>pcresyntax man page</h1>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
<p>
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.
<br>
<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 PROPERTY CODES FOR \p and \P</a>
<li><a name="TOC6" href="#SEC6">SCRIPT NAMES FOR \p AND \P</a>
<li><a name="TOC7" href="#SEC7">CHARACTER CLASSES</a>
<li><a name="TOC8" href="#SEC8">QUANTIFIERS</a>
<li><a name="TOC9" href="#SEC9">ANCHORS AND SIMPLE ASSERTIONS</a>
<li><a name="TOC10" href="#SEC10">MATCH POINT RESET</a>
<li><a name="TOC11" href="#SEC11">ALTERNATION</a>
<li><a name="TOC12" href="#SEC12">CAPTURING</a>
<li><a name="TOC13" href="#SEC13">ATOMIC GROUPS</a>
<li><a name="TOC14" href="#SEC14">COMMENT</a>
<li><a name="TOC15" href="#SEC15">OPTION SETTING</a>
<li><a name="TOC16" href="#SEC16">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
<li><a name="TOC17" href="#SEC17">BACKREFERENCES</a>
<li><a name="TOC18" href="#SEC18">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
<li><a name="TOC19" href="#SEC19">CONDITIONAL PATTERNS</a>
<li><a name="TOC20" href="#SEC20">BACKTRACKING CONTROL</a>
<li><a name="TOC21" href="#SEC21">NEWLINE CONVENTIONS</a>
<li><a name="TOC22" href="#SEC22">WHAT \R MATCHES</a>
<li><a name="TOC23" href="#SEC23">CALLOUTS</a>
<li><a name="TOC24" href="#SEC24">SEE ALSO</a>
<li><a name="TOC25" href="#SEC25">AUTHOR</a>
<li><a name="TOC26" href="#SEC26">REVISION</a>
</ul>
<br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
<P>
The full syntax and semantics of the regular expressions that are supported by
PCRE are described in the
<a href="pcrepattern.html"><b>pcrepattern</b></a>
documentation. This document contains just a quick-reference summary of the
syntax.
</P>
<br><a name="SEC2" href="#TOC1">QUOTING</a><br>
<P>
<pre>
  \x         where x is non-alphanumeric is a literal x
  \Q...\E    treat enclosed characters as literal
</PRE>
</P>
<br><a name="SEC3" href="#TOC1">CHARACTERS</a><br>
<P>
<pre>
  \a         alarm, that is, the BEL character (hex 07)
  \cx        "control-x", where x is any character
  \e         escape (hex 1B)
  \f         formfeed (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>
</P>
<br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br>
<P>
<pre>
  .          any character except newline;
               in dotall mode, any character whatsoever
  \C         one byte, even in UTF-8 mode (best avoided)
  \d         a decimal digit
  \D         a character that is not a decimal digit
  \h         a horizontal whitespace character
  \H         a character that is not a horizontal whitespace character
  \p{<i>xx</i>}     a character with the <i>xx</i> property
  \P{<i>xx</i>}     a character without the <i>xx</i> property
  \R         a newline sequence
  \s         a whitespace character
  \S         a character that is not a whitespace character
  \v         a vertical whitespace character
  \V         a character that is not a vertical whitespace character
  \w         a "word" character
  \W         a "non-word" character
  \X         an extended Unicode sequence
</pre>
In PCRE, \d, \D, \s, \S, \w, and \W recognize only ASCII characters.
</P>
<br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTY CODES FOR \p and \P</a><br>
<P>
<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>
</P>
<br><a name="SEC6" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
<P>
Arabic,
Armenian,
Balinese,
Bengali,
Bopomofo,
Braille,
Buginese,
Buhid,
Canadian_Aboriginal,
Cherokee,
Common,
Coptic,
Cuneiform,
Cypriot,
Cyrillic,
Deseret,
Devanagari,
Ethiopic,
Georgian,
Glagolitic,
Gothic,
Greek,
Gujarati,
Gurmukhi,
Han,
Hangul,
Hanunoo,
Hebrew,
Hiragana,
Inherited,
Kannada,
Katakana,
Kharoshthi,
Khmer,
Lao,
Latin,
Limbu,
Linear_B,
Malayalam,
Mongolian,
Myanmar,
New_Tai_Lue,
Nko,
Ogham,
Old_Italic,
Old_Persian,
Oriya,
Osmanya,
Phags_Pa,
Phoenician,
Runic,
Shavian,
Sinhala,
Syloti_Nagri,
Syriac,
Tagalog,
Tagbanwa,
Tai_Le,
Tamil,
Telugu,
Thaana,
Thai,
Tibetan,
Tifinagh,
Ugaritic,
Yi.
</P>
<br><a name="SEC7" href="#TOC1">CHARACTER CLASSES</a><br>
<P>
<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       whitespace
  upper       upper case letter
  word        same as \w
  xdigit      hexadecimal digit
</pre>
In PCRE, POSIX character set names recognize only ASCII characters. You can use
\Q...\E inside a character class.
</P>
<br><a name="SEC8" href="#TOC1">QUANTIFIERS</a><br>
<P>
<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>
</P>
<br><a name="SEC9" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
<P>
<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>
</P>
<br><a name="SEC10" href="#TOC1">MATCH POINT RESET</a><br>
<P>
<pre>
  \K          reset start of match
</PRE>
</P>
<br><a name="SEC11" href="#TOC1">ALTERNATION</a><br>
<P>
<pre>
  expr|expr|expr...
</PRE>
</P>
<br><a name="SEC12" href="#TOC1">CAPTURING</a><br>
<P>
<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>
</P>
<br><a name="SEC13" href="#TOC1">ATOMIC GROUPS</a><br>
<P>
<pre>
  (?&#62;...)        atomic, non-capturing group
</PRE>
</P>
<br><a name="SEC14" href="#TOC1">COMMENT</a><br>
<P>
<pre>
  (?#....)       comment (not nestable)
</PRE>
</P>
<br><a name="SEC15" href="#TOC1">OPTION SETTING</a><br>
<P>
<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>
</P>
<br><a name="SEC16" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
<P>
<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.
</P>
<br><a name="SEC17" href="#TOC1">BACKREFERENCES</a><br>
<P>
<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>
</P>
<br><a name="SEC18" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
<P>
<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)
</PRE>
</P>
<br><a name="SEC19" href="#TOC1">CONDITIONAL PATTERNS</a><br>
<P>
<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>
</P>
<br><a name="SEC20" href="#TOC1">BACKTRACKING CONTROL</a><br>
<P>
The following act immediately they are reached:
<pre>
  (*ACCEPT)      force successful match
  (*FAIL)        force backtrack; synonym (*F)
</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
  (*SKIP)        advance start to current matching position
  (*THEN)        local failure, backtrack to next alternation
</PRE>
</P>
<br><a name="SEC21" href="#TOC1">NEWLINE CONVENTIONS</a><br>
<P>
These are recognized only at the very start of the pattern or after a
(*BSR_...) option.
<pre>
  (*CR)
  (*LF)
  (*CRLF)
  (*ANYCRLF)
  (*ANY)
</PRE>
</P>
<br><a name="SEC22" href="#TOC1">WHAT \R MATCHES</a><br>
<P>
These are recognized only at the very start of the pattern or after a
(*...) option that sets the newline convention.
<pre>
  (*BSR_ANYCRLF)
  (*BSR_UNICODE)
</PRE>
</P>
<br><a name="SEC23" href="#TOC1">CALLOUTS</a><br>
<P>
<pre>
  (?C)      callout
  (?Cn)     callout with data n
</PRE>
</P>
<br><a name="SEC24" href="#TOC1">SEE ALSO</a><br>
<P>
<b>pcrepattern</b>(3), <b>pcreapi</b>(3), <b>pcrecallout</b>(3),
<b>pcrematching</b>(3), <b>pcre</b>(3).
</P>
<br><a name="SEC25" href="#TOC1">AUTHOR</a><br>
<P>
Philip Hazel
<br>
University Computing Service
<br>
Cambridge CB2 3QH, England.
<br>
</P>
<br><a name="SEC26" href="#TOC1">REVISION</a><br>
<P>
Last updated: 14 November 2007
<br>
Copyright &copy; 1997-2007 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.
</p>
1	ph10	208	<html>
2			<head>
3			<title>pcresyntax specification</title>
4			</head>
5			<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6			<h1>pcresyntax man page</h1>
7			<p>
8			Return to the <a href="index.html">PCRE index page</a>.
9			</p>
10			<p>
11			This page is part of the PCRE HTML documentation. It was generated automatically
12			from the original man page. If there is any nonsense in it, please consult the
13			man page, in case the conversion went wrong.
14			<br>
15			<ul>
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 PROPERTY CODES FOR \p and \P</a>
21			<li><a name="TOC6" href="#SEC6">SCRIPT NAMES FOR \p AND \P</a>
22			<li><a name="TOC7" href="#SEC7">CHARACTER CLASSES</a>
23			<li><a name="TOC8" href="#SEC8">QUANTIFIERS</a>
24			<li><a name="TOC9" href="#SEC9">ANCHORS AND SIMPLE ASSERTIONS</a>
25			<li><a name="TOC10" href="#SEC10">MATCH POINT RESET</a>
26			<li><a name="TOC11" href="#SEC11">ALTERNATION</a>
27			<li><a name="TOC12" href="#SEC12">CAPTURING</a>
28			<li><a name="TOC13" href="#SEC13">ATOMIC GROUPS</a>
29			<li><a name="TOC14" href="#SEC14">COMMENT</a>
30			<li><a name="TOC15" href="#SEC15">OPTION SETTING</a>
31			<li><a name="TOC16" href="#SEC16">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
32			<li><a name="TOC17" href="#SEC17">BACKREFERENCES</a>
33			<li><a name="TOC18" href="#SEC18">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
34			<li><a name="TOC19" href="#SEC19">CONDITIONAL PATTERNS</a>
35	ph10	211	<li><a name="TOC20" href="#SEC20">BACKTRACKING CONTROL</a>
36	ph10	227	<li><a name="TOC21" href="#SEC21">NEWLINE CONVENTIONS</a>
37	ph10	231	<li><a name="TOC22" href="#SEC22">WHAT \R MATCHES</a>
38			<li><a name="TOC23" href="#SEC23">CALLOUTS</a>
39			<li><a name="TOC24" href="#SEC24">SEE ALSO</a>
40			<li><a name="TOC25" href="#SEC25">AUTHOR</a>
41			<li><a name="TOC26" href="#SEC26">REVISION</a>
42	ph10	208	</ul>
43			<br><a name="SEC1" href="#TOC1">PCRE REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
44			<P>
45			The full syntax and semantics of the regular expressions that are supported by
46			PCRE are described in the
47			<a href="pcrepattern.html"><b>pcrepattern</b></a>
48			documentation. This document contains just a quick-reference summary of the
49			syntax.
50			</P>
51			<br><a name="SEC2" href="#TOC1">QUOTING</a><br>
52			<P>
53			<pre>
54			\x where x is non-alphanumeric is a literal x
55			\Q...\E treat enclosed characters as literal
56			</PRE>
57			</P>
58			<br><a name="SEC3" href="#TOC1">CHARACTERS</a><br>
59			<P>
60			<pre>
61			\a alarm, that is, the BEL character (hex 07)
62			\cx "control-x", where x is any character
63			\e escape (hex 1B)
64			\f formfeed (hex 0C)
65			\n newline (hex 0A)
66			\r carriage return (hex 0D)
67			\t tab (hex 09)
68			\ddd character with octal code ddd, or backreference
69			\xhh character with hex code hh
70			\x{hhh..} character with hex code hhh..
71			</PRE>
72			</P>
73			<br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br>
74			<P>
75			<pre>
76			. any character except newline;
77			in dotall mode, any character whatsoever
78			\C one byte, even in UTF-8 mode (best avoided)
79			\d a decimal digit
80			\D a character that is not a decimal digit
81			\h a horizontal whitespace character
82			\H a character that is not a horizontal whitespace character
83			\p{<i>xx</i>} a character with the <i>xx</i> property
84			\P{<i>xx</i>} a character without the <i>xx</i> property
85			\R a newline sequence
86			\s a whitespace character
87			\S a character that is not a whitespace character
88			\v a vertical whitespace character
89			\V a character that is not a vertical whitespace character
90			\w a "word" character
91			\W a "non-word" character
92			\X an extended Unicode sequence
93			</pre>
94			In PCRE, \d, \D, \s, \S, \w, and \W recognize only ASCII characters.
95			</P>
96			<br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTY CODES FOR \p and \P</a><br>
97			<P>
98			<pre>
99			C Other
100			Cc Control
101			Cf Format
102			Cn Unassigned
103			Co Private use
104			Cs Surrogate
105
106			L Letter
107			Ll Lower case letter
108			Lm Modifier letter
109			Lo Other letter
110			Lt Title case letter
111			Lu Upper case letter
112			L& Ll, Lu, or Lt
113
114			M Mark
115			Mc Spacing mark
116			Me Enclosing mark
117			Mn Non-spacing mark
118
119			N Number
120			Nd Decimal number
121			Nl Letter number
122			No Other number
123
124			P Punctuation
125			Pc Connector punctuation
126			Pd Dash punctuation
127			Pe Close punctuation
128			Pf Final punctuation
129			Pi Initial punctuation
130			Po Other punctuation
131			Ps Open punctuation
132
133			S Symbol
134			Sc Currency symbol
135			Sk Modifier symbol
136			Sm Mathematical symbol
137			So Other symbol
138
139			Z Separator
140			Zl Line separator
141			Zp Paragraph separator
142			Zs Space separator
143			</PRE>
144			</P>
145			<br><a name="SEC6" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
146			<P>
147			Arabic,
148			Armenian,
149			Balinese,
150			Bengali,
151			Bopomofo,
152			Braille,
153			Buginese,
154			Buhid,
155			Canadian_Aboriginal,
156			Cherokee,
157			Common,
158			Coptic,
159			Cuneiform,
160			Cypriot,
161			Cyrillic,
162			Deseret,
163			Devanagari,
164			Ethiopic,
165			Georgian,
166			Glagolitic,
167			Gothic,
168			Greek,
169			Gujarati,
170			Gurmukhi,
171			Han,
172			Hangul,
173			Hanunoo,
174			Hebrew,
175			Hiragana,
176			Inherited,
177			Kannada,
178			Katakana,
179			Kharoshthi,
180			Khmer,
181			Lao,
182			Latin,
183			Limbu,
184			Linear_B,
185			Malayalam,
186			Mongolian,
187			Myanmar,
188			New_Tai_Lue,
189			Nko,
190			Ogham,
191			Old_Italic,
192			Old_Persian,
193			Oriya,
194			Osmanya,
195			Phags_Pa,
196			Phoenician,
197			Runic,
198			Shavian,
199			Sinhala,
200			Syloti_Nagri,
201			Syriac,
202			Tagalog,
203			Tagbanwa,
204			Tai_Le,
205			Tamil,
206			Telugu,
207			Thaana,
208			Thai,
209			Tibetan,
210			Tifinagh,
211			Ugaritic,
212			Yi.
213			</P>
214			<br><a name="SEC7" href="#TOC1">CHARACTER CLASSES</a><br>
215			<P>
216			<pre>
217			[...] positive character class
218			[^...] negative character class
219			[x-y] range (can be used for hex characters)
220			[[:xxx:]] positive POSIX named set
221	ph10	286	[[:^xxx:]] negative POSIX named set
222	ph10	208
223			alnum alphanumeric
224			alpha alphabetic
225			ascii 0-127
226			blank space or tab
227			cntrl control character
228			digit decimal digit
229			graph printing, excluding space
230			lower lower case letter
231			print printing, including space
232			punct printing, excluding alphanumeric
233			space whitespace
234			upper upper case letter
235			word same as \w
236			xdigit hexadecimal digit
237			</pre>
238			In PCRE, POSIX character set names recognize only ASCII characters. You can use
239			\Q...\E inside a character class.
240			</P>
241			<br><a name="SEC8" href="#TOC1">QUANTIFIERS</a><br>
242			<P>
243			<pre>
244			? 0 or 1, greedy
245			?+ 0 or 1, possessive
246			?? 0 or 1, lazy
247			* 0 or more, greedy
248			*+ 0 or more, possessive
249			*? 0 or more, lazy
250			+ 1 or more, greedy
251			++ 1 or more, possessive
252			+? 1 or more, lazy
253			{n} exactly n
254			{n,m} at least n, no more than m, greedy
255			{n,m}+ at least n, no more than m, possessive
256			{n,m}? at least n, no more than m, lazy
257			{n,} n or more, greedy
258			{n,}+ n or more, possessive
259			{n,}? n or more, lazy
260			</PRE>
261			</P>
262			<br><a name="SEC9" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
263			<P>
264			<pre>
265			\b word boundary
266			\B not a word boundary
267			^ start of subject
268			also after internal newline in multiline mode
269			\A start of subject
270			$ end of subject
271			also before newline at end of subject
272			also before internal newline in multiline mode
273			\Z end of subject
274			also before newline at end of subject
275			\z end of subject
276			\G first matching position in subject
277			</PRE>
278			</P>
279			<br><a name="SEC10" href="#TOC1">MATCH POINT RESET</a><br>
280			<P>
281			<pre>
282			\K reset start of match
283			</PRE>
284			</P>
285			<br><a name="SEC11" href="#TOC1">ALTERNATION</a><br>
286			<P>
287			<pre>
288			expr\|expr\|expr...
289			</PRE>
290			</P>
291			<br><a name="SEC12" href="#TOC1">CAPTURING</a><br>
292			<P>
293			<pre>
294			(...) capturing group
295			(?<name>...) named capturing group (Perl)
296			(?'name'...) named capturing group (Perl)
297			(?P<name>...) named capturing group (Python)
298			(?:...) non-capturing group
299			(?\|...) non-capturing group; reset group numbers for
300			capturing groups in each alternative
301			</PRE>
302			</P>
303			<br><a name="SEC13" href="#TOC1">ATOMIC GROUPS</a><br>
304			<P>
305			<pre>
306			(?>...) atomic, non-capturing group
307			</PRE>
308			</P>
309			<br><a name="SEC14" href="#TOC1">COMMENT</a><br>
310			<P>
311			<pre>
312			(?#....) comment (not nestable)
313			</PRE>
314			</P>
315			<br><a name="SEC15" href="#TOC1">OPTION SETTING</a><br>
316			<P>
317			<pre>
318			(?i) caseless
319			(?J) allow duplicate names
320			(?m) multiline
321			(?s) single line (dotall)
322			(?U) default ungreedy (lazy)
323			(?x) extended (ignore white space)
324			(?-...) unset option(s)
325			</PRE>
326			</P>
327			<br><a name="SEC16" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
328			<P>
329			<pre>
330			(?=...) positive look ahead
331			(?!...) negative look ahead
332			(?<=...) positive look behind
333			(?<!...) negative look behind
334			</pre>
335			Each top-level branch of a look behind must be of a fixed length.
336			</P>
337			<br><a name="SEC17" href="#TOC1">BACKREFERENCES</a><br>
338			<P>
339			<pre>
340			\n reference by number (can be ambiguous)
341			\gn reference by number
342			\g{n} reference by number
343			\g{-n} relative reference by number
344			\k<name> reference by name (Perl)
345			\k'name' reference by name (Perl)
346			\g{name} reference by name (Perl)
347			\k{name} reference by name (.NET)
348			(?P=name) reference by name (Python)
349			</PRE>
350			</P>
351			<br><a name="SEC18" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
352			<P>
353			<pre>
354			(?R) recurse whole pattern
355			(?n) call subpattern by absolute number
356			(?+n) call subpattern by relative number
357			(?-n) call subpattern by relative number
358			(?&name) call subpattern by name (Perl)
359			(?P>name) call subpattern by name (Python)
360			</PRE>
361			</P>
362			<br><a name="SEC19" href="#TOC1">CONDITIONAL PATTERNS</a><br>
363			<P>
364			<pre>
365			(?(condition)yes-pattern)
366			(?(condition)yes-pattern\|no-pattern)
367
368			(?(n)... absolute reference condition
369			(?(+n)... relative reference condition
370			(?(-n)... relative reference condition
371			(?(<name>)... named reference condition (Perl)
372			(?('name')... named reference condition (Perl)
373			(?(name)... named reference condition (PCRE)
374			(?(R)... overall recursion condition
375			(?(Rn)... specific group recursion condition
376			(?(R&name)... specific recursion condition
377			(?(DEFINE)... define subpattern for reference
378			(?(assert)... assertion condition
379			</PRE>
380			</P>
381	ph10	211	<br><a name="SEC20" href="#TOC1">BACKTRACKING CONTROL</a><br>
382	ph10	208	<P>
383	ph10	211	The following act immediately they are reached:
384	ph10	208	<pre>
385	ph10	211	(*ACCEPT) force successful match
386			(FAIL) force backtrack; synonym (F)
387			</pre>
388			The following act only when a subsequent match failure causes a backtrack to
389			reach them. They all force a match failure, but they differ in what happens
390			afterwards. Those that advance the start-of-match point do so only if the
391			pattern is not anchored.
392			<pre>
393			(*COMMIT) overall failure, no advance of starting point
394			(*PRUNE) advance to next starting character
395			(*SKIP) advance start to current matching position
396			(*THEN) local failure, backtrack to next alternation
397			</PRE>
398			</P>
399	ph10	227	<br><a name="SEC21" href="#TOC1">NEWLINE CONVENTIONS</a><br>
400	ph10	211	<P>
401	ph10	261	These are recognized only at the very start of the pattern or after a
402			(*BSR_...) option.
403	ph10	211	<pre>
404	ph10	227	(*CR)
405			(*LF)
406			(*CRLF)
407			(*ANYCRLF)
408			(*ANY)
409			</PRE>
410			</P>
411	ph10	231	<br><a name="SEC22" href="#TOC1">WHAT \R MATCHES</a><br>
412	ph10	227	<P>
413	ph10	261	These are recognized only at the very start of the pattern or after a
414			(*...) option that sets the newline convention.
415	ph10	227	<pre>
416	ph10	231	(*BSR_ANYCRLF)
417			(*BSR_UNICODE)
418			</PRE>
419			</P>
420			<br><a name="SEC23" href="#TOC1">CALLOUTS</a><br>
421			<P>
422			<pre>
423	ph10	208	(?C) callout
424			(?Cn) callout with data n
425			</PRE>
426			</P>
427	ph10	231	<br><a name="SEC24" href="#TOC1">SEE ALSO</a><br>
428	ph10	208	<P>
429			<b>pcrepattern</b>(3), <b>pcreapi</b>(3), <b>pcrecallout</b>(3),
430			<b>pcrematching</b>(3), <b>pcre</b>(3).
431			</P>
432	ph10	231	<br><a name="SEC25" href="#TOC1">AUTHOR</a><br>
433	ph10	208	<P>
434			Philip Hazel
435			<br>
436			University Computing Service
437			<br>
438			Cambridge CB2 3QH, England.
439			<br>
440			</P>
441	ph10	231	<br><a name="SEC26" href="#TOC1">REVISION</a><br>
442	ph10	208	<P>
443	ph10	286	Last updated: 14 November 2007
444	ph10	208	<br>
445			Copyright © 1997-2007 University of Cambridge.
446			<br>
447			<p>
448			Return to the <a href="index.html">PCRE index page</a>.
449			</p>