trunk/doc/pcresyntax.3

.TH PCRESYNTAX 3 "08 January 2014" "PCRE 8.35"
.SH NAME
PCRE - Perl-compatible regular expressions
.SH "PCRE REGULAR EXPRESSION SYNTAX SUMMARY"
.rs
.sp
The full syntax and semantics of the regular expressions that are supported by
PCRE are described in the
.\" HREF
\fBpcrepattern\fP
.\"
documentation. This document contains a quick-reference summary of the syntax.
.
.
.SH "QUOTING"
.rs
.sp
  \ex         where x is non-alphanumeric is a literal x
  \eQ...\eE    treat enclosed characters as literal
.
.
.SH "CHARACTERS"
.rs
.sp
  \ea         alarm, that is, the BEL character (hex 07)
  \ecx        "control-x", where x is any ASCII character
  \ee         escape (hex 1B)
  \ef         form feed (hex 0C)
  \en         newline (hex 0A)
  \er         carriage return (hex 0D)
  \et         tab (hex 09)
  \e0dd       character with octal code 0dd
  \eddd       character with octal code ddd, or backreference
  \eo{ddd..}  character with octal code ddd..
  \exhh       character with hex code hh
  \ex{hhh..}  character with hex code hhh..
.sp
Note that \e0dd is always an octal code, and that \e8 and \e9 are the literal
characters "8" and "9".
.
.
.SH "CHARACTER TYPES"
.rs
.sp
  .          any character except newline;
               in dotall mode, any character whatsoever
  \eC         one data unit, even in UTF mode (best avoided)
  \ed         a decimal digit
  \eD         a character that is not a decimal digit
  \eh         a horizontal white space character
  \eH         a character that is not a horizontal white space character
  \eN         a character that is not a newline
  \ep{\fIxx\fP}     a character with the \fIxx\fP property
  \eP{\fIxx\fP}     a character without the \fIxx\fP property
  \eR         a newline sequence
  \es         a white space character
  \eS         a character that is not a white space character
  \ev         a vertical white space character
  \eV         a character that is not a vertical white space character
  \ew         a "word" character
  \eW         a "non-word" character
  \eX         a Unicode extended grapheme cluster
.sp
By default, \ed, \es, and \ew 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, \es and \ew 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.
.
.
.SH "GENERAL CATEGORY PROPERTIES FOR \ep and \eP"
.rs
.sp
  C          Other
  Cc         Control
  Cf         Format
  Cn         Unassigned
  Co         Private use
  Cs         Surrogate
.sp
  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
.sp
  M          Mark
  Mc         Spacing mark
  Me         Enclosing mark
  Mn         Non-spacing mark
.sp
  N          Number
  Nd         Decimal number
  Nl         Letter number
  No         Other number
.sp
  P          Punctuation
  Pc         Connector punctuation
  Pd         Dash punctuation
  Pe         Close punctuation
  Pf         Final punctuation
  Pi         Initial punctuation
  Po         Other punctuation
  Ps         Open punctuation
.sp
  S          Symbol
  Sc         Currency symbol
  Sk         Modifier symbol
  Sm         Mathematical symbol
  So         Other symbol
.sp
  Z          Separator
  Zl         Line separator
  Zp         Paragraph separator
  Zs         Space separator
.
.
.SH "PCRE SPECIAL CATEGORY PROPERTIES FOR \ep and \eP"
.rs
.sp
  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
.sp
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.
.
.
.SH "SCRIPT NAMES FOR \ep AND \eP"
.rs
.sp
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.
.
.
.SH "CHARACTER CLASSES"
.rs
.sp
  [...]       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
.sp
  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 \ew
  xdigit      hexadecimal digit
.sp
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.
.
.
.SH "QUANTIFIERS"
.rs
.sp
  ?           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
.
.
.SH "ANCHORS AND SIMPLE ASSERTIONS"
.rs
.sp
  \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
.
.
.SH "MATCH POINT RESET"
.rs
.sp
  \eK          reset start of match
.sp
\eK is honoured in positive assertions, but ignored in negative ones.
.
.
.SH "ALTERNATION"
.rs
.sp
  expr|expr|expr...
.
.
.SH "CAPTURING"
.rs
.sp
  (...)           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
.
.
.SH "ATOMIC GROUPS"
.rs
.sp
  (?>...)         atomic, non-capturing group
.
.
.
.
.SH "COMMENT"
.rs
.sp
  (?#....)        comment (not nestable)
.
.
.SH "OPTION SETTING"
.rs
.sp
  (?i)            caseless
  (?J)            allow duplicate names
  (?m)            multiline
  (?s)            single line (dotall)
  (?U)            default ungreedy (lazy)
  (?x)            extended (ignore white space)
  (?-...)         unset option(s)
.sp
The following are recognized only at the very start of a pattern or after one
of the newline or \eR options with similar syntax. More than one of them may
appear.
.sp
  (*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 \ed etc)
.sp
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.
.
.
.SH "NEWLINE CONVENTION"
.rs
.sp
These are recognized only at the very start of the pattern or after option
settings with a similar syntax.
.sp
  (*CR)           carriage return only
  (*LF)           linefeed only
  (*CRLF)         carriage return followed by linefeed
  (*ANYCRLF)      all three of the above
  (*ANY)          any Unicode newline sequence
.
.
.SH "WHAT \eR MATCHES"
.rs
.sp
These are recognized only at the very start of the pattern or after option
setting with a similar syntax.
.sp
  (*BSR_ANYCRLF)  CR, LF, or CRLF
  (*BSR_UNICODE)  any Unicode newline sequence
.
.
.SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS"
.rs
.sp
  (?=...)         positive look ahead
  (?!...)         negative look ahead
  (?<=...)        positive look behind
  (?<!...)        negative look behind
.sp
Each top-level branch of a look behind must be of a fixed length.
.
.
.SH "BACKREFERENCES"
.rs
.sp
  \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)
.
.
.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)"
.rs
.sp
  (?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)
.
.
.SH "CONDITIONAL PATTERNS"
.rs
.sp
  (?(condition)yes-pattern)
  (?(condition)yes-pattern|no-pattern)
.sp
  (?(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
.
.
.SH "BACKTRACKING CONTROL"
.rs
.sp
The following act immediately they are reached:
.sp
  (*ACCEPT)       force successful match
  (*FAIL)         force backtrack; synonym (*F)
  (*MARK:NAME)    set name to be passed back; synonym (*:NAME)
.sp
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.
.sp
  (*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)
.
.
.SH "CALLOUTS"
.rs
.sp
  (?C)      callout
  (?Cn)     callout with data n
.
.
.SH "SEE ALSO"
.rs
.sp
\fBpcrepattern\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3),
\fBpcrematching\fP(3), \fBpcre\fP(3).
.
.
.SH AUTHOR
.rs
.sp
.nf
Philip Hazel
University Computing Service
Cambridge CB2 3QH, England.
.fi
.
.
.SH REVISION
.rs
.sp
.nf
Last updated: 08 January 2014
Copyright (c) 1997-2014 University of Cambridge.
.fi
1	.TH PCRESYNTAX 3 "08 January 2014" "PCRE 8.35"
2	.SH NAME
3	PCRE - Perl-compatible regular expressions
4	.SH "PCRE REGULAR EXPRESSION SYNTAX SUMMARY"
5	.rs
6	.sp
7	The full syntax and semantics of the regular expressions that are supported by
8	PCRE are described in the
9	.\" HREF
10	\fBpcrepattern\fP
11	.\"
12	documentation. This document contains a quick-reference summary of the syntax.
13	.
14	.
15	.SH "QUOTING"
16	.rs
17	.sp
18	\ex where x is non-alphanumeric is a literal x
19	\eQ...\eE treat enclosed characters as literal
20	.
21	.
22	.SH "CHARACTERS"
23	.rs
24	.sp
25	\ea alarm, that is, the BEL character (hex 07)
26	\ecx "control-x", where x is any ASCII character
27	\ee escape (hex 1B)
28	\ef form feed (hex 0C)
29	\en newline (hex 0A)
30	\er carriage return (hex 0D)
31	\et tab (hex 09)
32	\e0dd character with octal code 0dd
33	\eddd character with octal code ddd, or backreference
34	\eo{ddd..} character with octal code ddd..
35	\exhh character with hex code hh
36	\ex{hhh..} character with hex code hhh..
37	.sp
38	Note that \e0dd is always an octal code, and that \e8 and \e9 are the literal
39	characters "8" and "9".
40	.
41	.
42	.SH "CHARACTER TYPES"
43	.rs
44	.sp
45	. any character except newline;
46	in dotall mode, any character whatsoever
47	\eC one data unit, even in UTF mode (best avoided)
48	\ed a decimal digit
49	\eD a character that is not a decimal digit
50	\eh a horizontal white space character
51	\eH a character that is not a horizontal white space character
52	\eN a character that is not a newline
53	\ep{\fIxx\fP} a character with the \fIxx\fP property
54	\eP{\fIxx\fP} a character without the \fIxx\fP property
55	\eR a newline sequence
56	\es a white space character
57	\eS a character that is not a white space character
58	\ev a vertical white space character
59	\eV a character that is not a vertical white space character
60	\ew a "word" character
61	\eW a "non-word" character
62	\eX a Unicode extended grapheme cluster
63	.sp
64	By default, \ed, \es, and \ew match only ASCII characters, even in UTF-8 mode
65	or in the 16- bit and 32-bit libraries. However, if locale-specific matching is
66	happening, \es and \ew may also match characters with code points in the range
67	128-255. If the PCRE_UCP option is set, the behaviour of these escape sequences
68	is changed to use Unicode properties and they match many more characters.
69	.
70	.
71	.SH "GENERAL CATEGORY PROPERTIES FOR \ep and \eP"
72	.rs
73	.sp
74	C Other
75	Cc Control
76	Cf Format
77	Cn Unassigned
78	Co Private use
79	Cs Surrogate
80	.sp
81	L Letter
82	Ll Lower case letter
83	Lm Modifier letter
84	Lo Other letter
85	Lt Title case letter
86	Lu Upper case letter
87	L& Ll, Lu, or Lt
88	.sp
89	M Mark
90	Mc Spacing mark
91	Me Enclosing mark
92	Mn Non-spacing mark
93	.sp
94	N Number
95	Nd Decimal number
96	Nl Letter number
97	No Other number
98	.sp
99	P Punctuation
100	Pc Connector punctuation
101	Pd Dash punctuation
102	Pe Close punctuation
103	Pf Final punctuation
104	Pi Initial punctuation
105	Po Other punctuation
106	Ps Open punctuation
107	.sp
108	S Symbol
109	Sc Currency symbol
110	Sk Modifier symbol
111	Sm Mathematical symbol
112	So Other symbol
113	.sp
114	Z Separator
115	Zl Line separator
116	Zp Paragraph separator
117	Zs Space separator
118	.
119	.
120	.SH "PCRE SPECIAL CATEGORY PROPERTIES FOR \ep and \eP"
121	.rs
122	.sp
123	Xan Alphanumeric: union of properties L and N
124	Xps POSIX space: property Z or tab, NL, VT, FF, CR
125	Xsp Perl space: property Z or tab, NL, VT, FF, CR
126	Xuc Univerally-named character: one that can be
127	represented by a Universal Character Name
128	Xwd Perl word: property Xan or underscore
129	.sp
130	Perl and POSIX space are now the same. Perl added VT to its space character set
131	at release 5.18 and PCRE changed at release 8.34.
132	.
133	.
134	.SH "SCRIPT NAMES FOR \ep AND \eP"
135	.rs
136	.sp
137	Arabic,
138	Armenian,
139	Avestan,
140	Balinese,
141	Bamum,
142	Bassa_Vah,
143	Batak,
144	Bengali,
145	Bopomofo,
146	Brahmi,
147	Braille,
148	Buginese,
149	Buhid,
150	Canadian_Aboriginal,
151	Carian,
152	Caucasian_Albanian,
153	Chakma,
154	Cham,
155	Cherokee,
156	Common,
157	Coptic,
158	Cuneiform,
159	Cypriot,
160	Cyrillic,
161	Deseret,
162	Devanagari,
163	Duployan,
164	Egyptian_Hieroglyphs,
165	Elbasan,
166	Ethiopic,
167	Georgian,
168	Glagolitic,
169	Gothic,
170	Grantha,
171	Greek,
172	Gujarati,
173	Gurmukhi,
174	Han,
175	Hangul,
176	Hanunoo,
177	Hebrew,
178	Hiragana,
179	Imperial_Aramaic,
180	Inherited,
181	Inscriptional_Pahlavi,
182	Inscriptional_Parthian,
183	Javanese,
184	Kaithi,
185	Kannada,
186	Katakana,
187	Kayah_Li,
188	Kharoshthi,
189	Khmer,
190	Khojki,
191	Khudawadi,
192	Lao,
193	Latin,
194	Lepcha,
195	Limbu,
196	Linear_A,
197	Linear_B,
198	Lisu,
199	Lycian,
200	Lydian,
201	Mahajani,
202	Malayalam,
203	Mandaic,
204	Manichaean,
205	Meetei_Mayek,
206	Mende_Kikakui,
207	Meroitic_Cursive,
208	Meroitic_Hieroglyphs,
209	Miao,
210	Modi,
211	Mongolian,
212	Mro,
213	Myanmar,
214	Nabataean,
215	New_Tai_Lue,
216	Nko,
217	Ogham,
218	Ol_Chiki,
219	Old_Italic,
220	Old_North_Arabian,
221	Old_Permic,
222	Old_Persian,
223	Old_South_Arabian,
224	Old_Turkic,
225	Oriya,
226	Osmanya,
227	Pahawh_Hmong,
228	Palmyrene,
229	Pau_Cin_Hau,
230	Phags_Pa,
231	Phoenician,
232	Psalter_Pahlavi,
233	Rejang,
234	Runic,
235	Samaritan,
236	Saurashtra,
237	Sharada,
238	Shavian,
239	Siddham,
240	Sinhala,
241	Sora_Sompeng,
242	Sundanese,
243	Syloti_Nagri,
244	Syriac,
245	Tagalog,
246	Tagbanwa,
247	Tai_Le,
248	Tai_Tham,
249	Tai_Viet,
250	Takri,
251	Tamil,
252	Telugu,
253	Thaana,
254	Thai,
255	Tibetan,
256	Tifinagh,
257	Tirhuta,
258	Ugaritic,
259	Vai,
260	Warang_Citi,
261	Yi.
262	.
263	.
264	.SH "CHARACTER CLASSES"
265	.rs
266	.sp
267	[...] positive character class
268	[^...] negative character class
269	[x-y] range (can be used for hex characters)
270	[[:xxx:]] positive POSIX named set
271	[[:^xxx:]] negative POSIX named set
272	.sp
273	alnum alphanumeric
274	alpha alphabetic
275	ascii 0-127
276	blank space or tab
277	cntrl control character
278	digit decimal digit
279	graph printing, excluding space
280	lower lower case letter
281	print printing, including space
282	punct printing, excluding alphanumeric
283	space white space
284	upper upper case letter
285	word same as \ew
286	xdigit hexadecimal digit
287	.sp
288	In PCRE, POSIX character set names recognize only ASCII characters by default,
289	but some of them use Unicode properties if PCRE_UCP is set. You can use
290	\eQ...\eE inside a character class.
291	.
292	.
293	.SH "QUANTIFIERS"
294	.rs
295	.sp
296	? 0 or 1, greedy
297	?+ 0 or 1, possessive
298	?? 0 or 1, lazy
299	* 0 or more, greedy
300	*+ 0 or more, possessive
301	*? 0 or more, lazy
302	+ 1 or more, greedy
303	++ 1 or more, possessive
304	+? 1 or more, lazy
305	{n} exactly n
306	{n,m} at least n, no more than m, greedy
307	{n,m}+ at least n, no more than m, possessive
308	{n,m}? at least n, no more than m, lazy
309	{n,} n or more, greedy
310	{n,}+ n or more, possessive
311	{n,}? n or more, lazy
312	.
313	.
314	.SH "ANCHORS AND SIMPLE ASSERTIONS"
315	.rs
316	.sp
317	\eb word boundary
318	\eB not a word boundary
319	^ start of subject
320	also after internal newline in multiline mode
321	\eA start of subject
322	$ end of subject
323	also before newline at end of subject
324	also before internal newline in multiline mode
325	\eZ end of subject
326	also before newline at end of subject
327	\ez end of subject
328	\eG first matching position in subject
329	.
330	.
331	.SH "MATCH POINT RESET"
332	.rs
333	.sp
334	\eK reset start of match
335	.sp
336	\eK is honoured in positive assertions, but ignored in negative ones.
337	.
338	.
339	.SH "ALTERNATION"
340	.rs
341	.sp
342	expr\|expr\|expr...
343	.
344	.
345	.SH "CAPTURING"
346	.rs
347	.sp
348	(...) capturing group
349	(?<name>...) named capturing group (Perl)
350	(?'name'...) named capturing group (Perl)
351	(?P<name>...) named capturing group (Python)
352	(?:...) non-capturing group
353	(?\|...) non-capturing group; reset group numbers for
354	capturing groups in each alternative
355	.
356	.
357	.SH "ATOMIC GROUPS"
358	.rs
359	.sp
360	(?>...) atomic, non-capturing group
361	.
362	.
363	.
364	.
365	.SH "COMMENT"
366	.rs
367	.sp
368	(?#....) comment (not nestable)
369	.
370	.
371	.SH "OPTION SETTING"
372	.rs
373	.sp
374	(?i) caseless
375	(?J) allow duplicate names
376	(?m) multiline
377	(?s) single line (dotall)
378	(?U) default ungreedy (lazy)
379	(?x) extended (ignore white space)
380	(?-...) unset option(s)
381	.sp
382	The following are recognized only at the very start of a pattern or after one
383	of the newline or \eR options with similar syntax. More than one of them may
384	appear.
385	.sp
386	(*LIMIT_MATCH=d) set the match limit to d (decimal number)
387	(*LIMIT_RECURSION=d) set the recursion limit to d (decimal number)
388	(*NO_AUTO_POSSESS) no auto-possessification (PCRE_NO_AUTO_POSSESS)
389	(*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)
390	(*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8)
391	(*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16)
392	(*UTF32) set UTF-32 mode: 32-bit library (PCRE_UTF32)
393	(*UTF) set appropriate UTF mode for the library in use
394	(*UCP) set PCRE_UCP (use Unicode properties for \ed etc)
395	.sp
396	Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the
397	limits set by the caller of pcre_exec(), not increase them.
398	.
399	.
400	.SH "NEWLINE CONVENTION"
401	.rs
402	.sp
403	These are recognized only at the very start of the pattern or after option
404	settings with a similar syntax.
405	.sp
406	(*CR) carriage return only
407	(*LF) linefeed only
408	(*CRLF) carriage return followed by linefeed
409	(*ANYCRLF) all three of the above
410	(*ANY) any Unicode newline sequence
411	.
412	.
413	.SH "WHAT \eR MATCHES"
414	.rs
415	.sp
416	These are recognized only at the very start of the pattern or after option
417	setting with a similar syntax.
418	.sp
419	(*BSR_ANYCRLF) CR, LF, or CRLF
420	(*BSR_UNICODE) any Unicode newline sequence
421	.
422	.
423	.SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS"
424	.rs
425	.sp
426	(?=...) positive look ahead
427	(?!...) negative look ahead
428	(?<=...) positive look behind
429	(?<!...) negative look behind
430	.sp
431	Each top-level branch of a look behind must be of a fixed length.
432	.
433	.
434	.SH "BACKREFERENCES"
435	.rs
436	.sp
437	\en reference by number (can be ambiguous)
438	\egn reference by number
439	\eg{n} reference by number
440	\eg{-n} relative reference by number
441	\ek<name> reference by name (Perl)
442	\ek'name' reference by name (Perl)
443	\eg{name} reference by name (Perl)
444	\ek{name} reference by name (.NET)
445	(?P=name) reference by name (Python)
446	.
447	.
448	.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)"
449	.rs
450	.sp
451	(?R) recurse whole pattern
452	(?n) call subpattern by absolute number
453	(?+n) call subpattern by relative number
454	(?-n) call subpattern by relative number
455	(?&name) call subpattern by name (Perl)
456	(?P>name) call subpattern by name (Python)
457	\eg<name> call subpattern by name (Oniguruma)
458	\eg'name' call subpattern by name (Oniguruma)
459	\eg<n> call subpattern by absolute number (Oniguruma)
460	\eg'n' call subpattern by absolute number (Oniguruma)
461	\eg<+n> call subpattern by relative number (PCRE extension)
462	\eg'+n' call subpattern by relative number (PCRE extension)
463	\eg<-n> call subpattern by relative number (PCRE extension)
464	\eg'-n' call subpattern by relative number (PCRE extension)
465	.
466	.
467	.SH "CONDITIONAL PATTERNS"
468	.rs
469	.sp
470	(?(condition)yes-pattern)
471	(?(condition)yes-pattern\|no-pattern)
472	.sp
473	(?(n)... absolute reference condition
474	(?(+n)... relative reference condition
475	(?(-n)... relative reference condition
476	(?(<name>)... named reference condition (Perl)
477	(?('name')... named reference condition (Perl)
478	(?(name)... named reference condition (PCRE)
479	(?(R)... overall recursion condition
480	(?(Rn)... specific group recursion condition
481	(?(R&name)... specific recursion condition
482	(?(DEFINE)... define subpattern for reference
483	(?(assert)... assertion condition
484	.
485	.
486	.SH "BACKTRACKING CONTROL"
487	.rs
488	.sp
489	The following act immediately they are reached:
490	.sp
491	(*ACCEPT) force successful match
492	(FAIL) force backtrack; synonym (F)
493	(MARK:NAME) set name to be passed back; synonym (:NAME)
494	.sp
495	The following act only when a subsequent match failure causes a backtrack to
496	reach them. They all force a match failure, but they differ in what happens
497	afterwards. Those that advance the start-of-match point do so only if the
498	pattern is not anchored.
499	.sp
500	(*COMMIT) overall failure, no advance of starting point
501	(*PRUNE) advance to next starting character
502	(PRUNE:NAME) equivalent to (MARK:NAME)(*PRUNE)
503	(*SKIP) advance to current matching position
504	(*SKIP:NAME) advance to position corresponding to an earlier
505	(MARK:NAME); if not found, the (SKIP) is ignored
506	(*THEN) local failure, backtrack to next alternation
507	(THEN:NAME) equivalent to (MARK:NAME)(*THEN)
508	.
509	.
510	.SH "CALLOUTS"
511	.rs
512	.sp
513	(?C) callout
514	(?Cn) callout with data n
515	.
516	.
517	.SH "SEE ALSO"
518	.rs
519	.sp
520	\fBpcrepattern\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3),
521	\fBpcrematching\fP(3), \fBpcre\fP(3).
522	.
523	.
524	.SH AUTHOR
525	.rs
526	.sp
527	.nf
528	Philip Hazel
529	University Computing Service
530	Cambridge CB2 3QH, England.
531	.fi
532	.
533	.
534	.SH REVISION
535	.rs
536	.sp
537	.nf
538	Last updated: 08 January 2014
539	Copyright (c) 1997-2014 University of Cambridge.
540	.fi