1<html> 2<head> 3<title>pcre2syntax specification</title> 4</head> 5<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6<h1>pcre2syntax man page</h1> 7<p> 8Return to the <a href="index.html">PCRE2 index page</a>. 9</p> 10<p> 11This page is part of the PCRE2 HTML documentation. It was generated 12automatically from the original man page. If there is any nonsense in it, 13please consult the man page, in case the conversion went wrong. 14<br> 15<ul> 16<li><a name="TOC1" href="#SEC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a> 17<li><a name="TOC2" href="#SEC2">QUOTING</a> 18<li><a name="TOC3" href="#SEC3">BRACED ITEMS</a> 19<li><a name="TOC4" href="#SEC4">ESCAPED CHARACTERS</a> 20<li><a name="TOC5" href="#SEC5">CHARACTER TYPES</a> 21<li><a name="TOC6" href="#SEC6">GENERAL CATEGORY PROPERTIES FOR \p and \P</a> 22<li><a name="TOC7" href="#SEC7">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a> 23<li><a name="TOC8" href="#SEC8">BINARY PROPERTIES FOR \p AND \P</a> 24<li><a name="TOC9" href="#SEC9">SCRIPT MATCHING WITH \p AND \P</a> 25<li><a name="TOC10" href="#SEC10">THE BIDI_CLASS PROPERTY FOR \p AND \P</a> 26<li><a name="TOC11" href="#SEC11">CHARACTER CLASSES</a> 27<li><a name="TOC12" href="#SEC12">QUANTIFIERS</a> 28<li><a name="TOC13" href="#SEC13">ANCHORS AND SIMPLE ASSERTIONS</a> 29<li><a name="TOC14" href="#SEC14">REPORTED MATCH POINT SETTING</a> 30<li><a name="TOC15" href="#SEC15">ALTERNATION</a> 31<li><a name="TOC16" href="#SEC16">CAPTURING</a> 32<li><a name="TOC17" href="#SEC17">ATOMIC GROUPS</a> 33<li><a name="TOC18" href="#SEC18">COMMENT</a> 34<li><a name="TOC19" href="#SEC19">OPTION SETTING</a> 35<li><a name="TOC20" href="#SEC20">NEWLINE CONVENTION</a> 36<li><a name="TOC21" href="#SEC21">WHAT \R MATCHES</a> 37<li><a name="TOC22" href="#SEC22">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a> 38<li><a name="TOC23" href="#SEC23">NON-ATOMIC LOOKAROUND ASSERTIONS</a> 39<li><a name="TOC24" href="#SEC24">SCRIPT RUNS</a> 40<li><a name="TOC25" href="#SEC25">BACKREFERENCES</a> 41<li><a name="TOC26" href="#SEC26">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a> 42<li><a name="TOC27" href="#SEC27">CONDITIONAL PATTERNS</a> 43<li><a name="TOC28" href="#SEC28">BACKTRACKING CONTROL</a> 44<li><a name="TOC29" href="#SEC29">CALLOUTS</a> 45<li><a name="TOC30" href="#SEC30">SEE ALSO</a> 46<li><a name="TOC31" href="#SEC31">AUTHOR</a> 47<li><a name="TOC32" href="#SEC32">REVISION</a> 48</ul> 49<br><a name="SEC1" href="#TOC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a><br> 50<P> 51The full syntax and semantics of the regular expressions that are supported by 52PCRE2 are described in the 53<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 54documentation. This document contains a quick-reference summary of the syntax. 55</P> 56<br><a name="SEC2" href="#TOC1">QUOTING</a><br> 57<P> 58<pre> 59 \x where x is non-alphanumeric is a literal x 60 \Q...\E treat enclosed characters as literal 61</pre> 62Note that white space inside \Q...\E is always treated as literal, even if 63PCRE2_EXTENDED is set, causing most other white space to be ignored. 64</P> 65<br><a name="SEC3" href="#TOC1">BRACED ITEMS</a><br> 66<P> 67With one exception, wherever brace characters { and } are required to enclose 68data for constructions such as \g{2} or \k{name}, space and/or horizontal tab 69characters that follow { or precede } are allowed and are ignored. In the case 70of quantifiers, they may also appear before or after the comma. The exception 71is \u{...} which is not Perl-compatible and is recognized only when 72PCRE2_EXTRA_ALT_BSUX is set. This is an ECMAScript compatibility feature, and 73follows ECMAScript's behaviour. 74</P> 75<br><a name="SEC4" href="#TOC1">ESCAPED CHARACTERS</a><br> 76<P> 77This table applies to ASCII and Unicode environments. An unrecognized escape 78sequence causes an error. 79<pre> 80 \a alarm, that is, the BEL character (hex 07) 81 \cx "control-x", where x is a non-control ASCII character 82 \e escape (hex 1B) 83 \f form feed (hex 0C) 84 \n newline (hex 0A) 85 \r carriage return (hex 0D) 86 \t tab (hex 09) 87 \0dd character with octal code 0dd 88 \ddd character with octal code ddd, or backreference 89 \o{ddd..} character with octal code ddd.. 90 \N{U+hh..} character with Unicode code point hh.. (Unicode mode only) 91 \xhh character with hex code hh 92 \x{hh..} character with hex code hh.. 93</pre> 94If PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX is set ("ALT_BSUX mode"), the 95following are also recognized: 96<pre> 97 \U the character "U" 98 \uhhhh character with hex code hhhh 99 \u{hh..} character with hex code hh.. but only for EXTRA_ALT_BSUX 100</pre> 101When \x is not followed by {, from zero to two hexadecimal digits are read, 102but in ALT_BSUX mode \x must be followed by two hexadecimal digits to be 103recognized as a hexadecimal escape; otherwise it matches a literal "x". 104Likewise, if \u (in ALT_BSUX mode) is not followed by four hexadecimal digits 105or (in EXTRA_ALT_BSUX mode) a sequence of hex digits in curly brackets, it 106matches a literal "u". 107</P> 108<P> 109Note that \0dd is always an octal code. The treatment of backslash followed by 110a non-zero digit is complicated; for details see the section 111<a href="pcre2pattern.html#digitsafterbackslash">"Non-printing characters"</a> 112in the 113<a href="pcre2pattern.html"><b>pcre2pattern</b></a> 114documentation, where details of escape processing in EBCDIC environments are 115also given. \N{U+hh..} is synonymous with \x{hh..} in PCRE2 but is not 116supported in EBCDIC environments. Note that \N not followed by an opening 117curly bracket has a different meaning (see below). 118</P> 119<br><a name="SEC5" href="#TOC1">CHARACTER TYPES</a><br> 120<P> 121<pre> 122 . any character except newline; 123 in dotall mode, any character whatsoever 124 \C one code unit, even in UTF mode (best avoided) 125 \d a decimal digit 126 \D a character that is not a decimal digit 127 \h a horizontal white space character 128 \H a character that is not a horizontal white space character 129 \N a character that is not a newline 130 \p{<i>xx</i>} a character with the <i>xx</i> property 131 \P{<i>xx</i>} a character without the <i>xx</i> property 132 \R a newline sequence 133 \s a white space character 134 \S a character that is not a white space character 135 \v a vertical white space character 136 \V a character that is not a vertical white space character 137 \w a "word" character 138 \W a "non-word" character 139 \X a Unicode extended grapheme cluster 140</pre> 141\C is dangerous because it may leave the current matching point in the middle 142of a UTF-8 or UTF-16 character. The application can lock out the use of \C by 143setting the PCRE2_NEVER_BACKSLASH_C option. It is also possible to build PCRE2 144with the use of \C permanently disabled. 145</P> 146<P> 147By default, \d, \s, and \w match only ASCII characters, even in UTF-8 mode 148or in the 16-bit and 32-bit libraries. However, if locale-specific matching is 149happening, \s and \w may also match characters with code points in the range 150128-255. If the PCRE2_UCP option is set, the behaviour of these escape 151sequences is changed to use Unicode properties and they match many more 152characters, but there are some option settings that can restrict individual 153sequences to matching only ASCII characters. 154</P> 155<P> 156Property descriptions in \p and \P are matched caselessly; hyphens, 157underscores, and white space are ignored, in accordance with Unicode's "loose 158matching" rules. 159</P> 160<br><a name="SEC6" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a><br> 161<P> 162<pre> 163 C Other 164 Cc Control 165 Cf Format 166 Cn Unassigned 167 Co Private use 168 Cs Surrogate 169 170 L Letter 171 Ll Lower case letter 172 Lm Modifier letter 173 Lo Other letter 174 Lt Title case letter 175 Lu Upper case letter 176 Lc Ll, Lu, or Lt 177 L& Ll, Lu, or Lt 178 179 M Mark 180 Mc Spacing mark 181 Me Enclosing mark 182 Mn Non-spacing mark 183 184 N Number 185 Nd Decimal number 186 Nl Letter number 187 No Other number 188 189 P Punctuation 190 Pc Connector punctuation 191 Pd Dash punctuation 192 Pe Close punctuation 193 Pf Final punctuation 194 Pi Initial punctuation 195 Po Other punctuation 196 Ps Open punctuation 197 198 S Symbol 199 Sc Currency symbol 200 Sk Modifier symbol 201 Sm Mathematical symbol 202 So Other symbol 203 204 Z Separator 205 Zl Line separator 206 Zp Paragraph separator 207 Zs Space separator 208</PRE> 209</P> 210<br><a name="SEC7" href="#TOC1">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br> 211<P> 212<pre> 213 Xan Alphanumeric: union of properties L and N 214 Xps POSIX space: property Z or tab, NL, VT, FF, CR 215 Xsp Perl space: property Z or tab, NL, VT, FF, CR 216 Xuc Universally-named character: one that can be 217 represented by a Universal Character Name 218 Xwd Perl word: property Xan or underscore 219</pre> 220Perl and POSIX space are now the same. Perl added VT to its space character set 221at release 5.18. 222</P> 223<br><a name="SEC8" href="#TOC1">BINARY PROPERTIES FOR \p AND \P</a><br> 224<P> 225Unicode defines a number of binary properties, that is, properties whose only 226values are true or false. You can obtain a list of those that are recognized by 227\p and \P, along with their abbreviations, by running this command: 228<pre> 229 pcre2test -LP 230</PRE> 231</P> 232<br><a name="SEC9" href="#TOC1">SCRIPT MATCHING WITH \p AND \P</a><br> 233<P> 234Many script names and their 4-letter abbreviations are recognized in 235\p{sc:...} or \p{scx:...} items, or on their own with \p (and also \P of 236course). You can obtain a list of these scripts by running this command: 237<pre> 238 pcre2test -LS 239</PRE> 240</P> 241<br><a name="SEC10" href="#TOC1">THE BIDI_CLASS PROPERTY FOR \p AND \P</a><br> 242<P> 243<pre> 244 \p{Bidi_Class:<class>} matches a character with the given class 245 \p{BC:<class>} matches a character with the given class 246</pre> 247The recognized classes are: 248<pre> 249 AL Arabic letter 250 AN Arabic number 251 B paragraph separator 252 BN boundary neutral 253 CS common separator 254 EN European number 255 ES European separator 256 ET European terminator 257 FSI first strong isolate 258 L left-to-right 259 LRE left-to-right embedding 260 LRI left-to-right isolate 261 LRO left-to-right override 262 NSM non-spacing mark 263 ON other neutral 264 PDF pop directional format 265 PDI pop directional isolate 266 R right-to-left 267 RLE right-to-left embedding 268 RLI right-to-left isolate 269 RLO right-to-left override 270 S segment separator 271 WS which space 272</PRE> 273</P> 274<br><a name="SEC11" href="#TOC1">CHARACTER CLASSES</a><br> 275<P> 276<pre> 277 [...] positive character class 278 [^...] negative character class 279 [x-y] range (can be used for hex characters) 280 [[:xxx:]] positive POSIX named set 281 [[:^xxx:]] negative POSIX named set 282 283 alnum alphanumeric 284 alpha alphabetic 285 ascii 0-127 286 blank space or tab 287 cntrl control character 288 digit decimal digit 289 graph printing, excluding space 290 lower lower case letter 291 print printing, including space 292 punct printing, excluding alphanumeric 293 space white space 294 upper upper case letter 295 word same as \w 296 xdigit hexadecimal digit 297</pre> 298In PCRE2, POSIX character set names recognize only ASCII characters by default, 299but some of them use Unicode properties if PCRE2_UCP is set. You can use 300\Q...\E inside a character class. 301</P> 302<br><a name="SEC12" href="#TOC1">QUANTIFIERS</a><br> 303<P> 304<pre> 305 ? 0 or 1, greedy 306 ?+ 0 or 1, possessive 307 ?? 0 or 1, lazy 308 * 0 or more, greedy 309 *+ 0 or more, possessive 310 *? 0 or more, lazy 311 + 1 or more, greedy 312 ++ 1 or more, possessive 313 +? 1 or more, lazy 314 {n} exactly n 315 {n,m} at least n, no more than m, greedy 316 {n,m}+ at least n, no more than m, possessive 317 {n,m}? at least n, no more than m, lazy 318 {n,} n or more, greedy 319 {n,}+ n or more, possessive 320 {n,}? n or more, lazy 321 {,m} zero up to m, greedy 322 {,m}+ zero up to m, possessive 323 {,m}? zero up to m, lazy 324</PRE> 325</P> 326<br><a name="SEC13" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br> 327<P> 328<pre> 329 \b word boundary 330 \B not a word boundary 331 ^ start of subject 332 also after an internal newline in multiline mode 333 (after any newline if PCRE2_ALT_CIRCUMFLEX is set) 334 \A start of subject 335 $ end of subject 336 also before newline at end of subject 337 also before internal newline in multiline mode 338 \Z end of subject 339 also before newline at end of subject 340 \z end of subject 341 \G first matching position in subject 342</PRE> 343</P> 344<br><a name="SEC14" href="#TOC1">REPORTED MATCH POINT SETTING</a><br> 345<P> 346<pre> 347 \K set reported start of match 348</pre> 349From release 10.38 \K is not permitted by default in lookaround assertions, 350for compatibility with Perl. However, if the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK 351option is set, the previous behaviour is re-enabled. When this option is set, 352\K is honoured in positive assertions, but ignored in negative ones. 353</P> 354<br><a name="SEC15" href="#TOC1">ALTERNATION</a><br> 355<P> 356<pre> 357 expr|expr|expr... 358</PRE> 359</P> 360<br><a name="SEC16" href="#TOC1">CAPTURING</a><br> 361<P> 362<pre> 363 (...) capture group 364 (?<name>...) named capture group (Perl) 365 (?'name'...) named capture group (Perl) 366 (?P<name>...) named capture group (Python) 367 (?:...) non-capture group 368 (?|...) non-capture group; reset group numbers for 369 capture groups in each alternative 370</pre> 371In non-UTF modes, names may contain underscores and ASCII letters and digits; 372in UTF modes, any Unicode letters and Unicode decimal digits are permitted. In 373both cases, a name must not start with a digit. 374</P> 375<br><a name="SEC17" href="#TOC1">ATOMIC GROUPS</a><br> 376<P> 377<pre> 378 (?>...) atomic non-capture group 379 (*atomic:...) atomic non-capture group 380</PRE> 381</P> 382<br><a name="SEC18" href="#TOC1">COMMENT</a><br> 383<P> 384<pre> 385 (?#....) comment (not nestable) 386</PRE> 387</P> 388<br><a name="SEC19" href="#TOC1">OPTION SETTING</a><br> 389<P> 390Changes of these options within a group are automatically cancelled at the end 391of the group. 392<pre> 393 (?a) all ASCII options 394 (?aD) restrict \d to ASCII in UCP mode 395 (?aS) restrict \s to ASCII in UCP mode 396 (?aW) restrict \w to ASCII in UCP mode 397 (?aP) restrict all POSIX classes to ASCII in UCP mode 398 (?aT) restrict POSIX digit classes to ASCII in UCP mode 399 (?i) caseless 400 (?J) allow duplicate named groups 401 (?m) multiline 402 (?n) no auto capture 403 (?r) restrict caseless to either ASCII or non-ASCII 404 (?s) single line (dotall) 405 (?U) default ungreedy (lazy) 406 (?x) ignore white space except in classes or \Q...\E 407 (?xx) as (?x) but also ignore space and tab in classes 408 (?-...) unset the given option(s) 409 (?^) unset imnrsx options 410</pre> 411(?aP) implies (?aT) as well, though this has no additional effect. However, it 412means that (?-aP) is really (?-PT) which disables all ASCII restrictions for 413POSIX classes. 414</P> 415<P> 416Unsetting x or xx unsets both. Several options may be set at once, and a 417mixture of setting and unsetting such as (?i-x) is allowed, but there may be 418only one hyphen. Setting (but no unsetting) is allowed after (?^ for example 419(?^in). An option setting may appear at the start of a non-capture group, for 420example (?i:...). 421</P> 422<P> 423The following are recognized only at the very start of a pattern or after one 424of the newline or \R options with similar syntax. More than one of them may 425appear. For the first three, d is a decimal number. 426<pre> 427 (*LIMIT_DEPTH=d) set the backtracking limit to d 428 (*LIMIT_HEAP=d) set the heap size limit to d * 1024 bytes 429 (*LIMIT_MATCH=d) set the match limit to d 430 (*NOTEMPTY) set PCRE2_NOTEMPTY when matching 431 (*NOTEMPTY_ATSTART) set PCRE2_NOTEMPTY_ATSTART when matching 432 (*NO_AUTO_POSSESS) no auto-possessification (PCRE2_NO_AUTO_POSSESS) 433 (*NO_DOTSTAR_ANCHOR) no .* anchoring (PCRE2_NO_DOTSTAR_ANCHOR) 434 (*NO_JIT) disable JIT optimization 435 (*NO_START_OPT) no start-match optimization (PCRE2_NO_START_OPTIMIZE) 436 (*UTF) set appropriate UTF mode for the library in use 437 (*UCP) set PCRE2_UCP (use Unicode properties for \d etc) 438</pre> 439Note that LIMIT_DEPTH, LIMIT_HEAP, and LIMIT_MATCH can only reduce the value of 440the limits set by the caller of <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b>, 441not increase them. LIMIT_RECURSION is an obsolete synonym for LIMIT_DEPTH. The 442application can lock out the use of (*UTF) and (*UCP) by setting the 443PCRE2_NEVER_UTF or PCRE2_NEVER_UCP options, respectively, at compile time. 444</P> 445<br><a name="SEC20" href="#TOC1">NEWLINE CONVENTION</a><br> 446<P> 447These are recognized only at the very start of the pattern or after option 448settings with a similar syntax. 449<pre> 450 (*CR) carriage return only 451 (*LF) linefeed only 452 (*CRLF) carriage return followed by linefeed 453 (*ANYCRLF) all three of the above 454 (*ANY) any Unicode newline sequence 455 (*NUL) the NUL character (binary zero) 456</PRE> 457</P> 458<br><a name="SEC21" href="#TOC1">WHAT \R MATCHES</a><br> 459<P> 460These are recognized only at the very start of the pattern or after option 461setting with a similar syntax. 462<pre> 463 (*BSR_ANYCRLF) CR, LF, or CRLF 464 (*BSR_UNICODE) any Unicode newline sequence 465</PRE> 466</P> 467<br><a name="SEC22" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br> 468<P> 469<pre> 470 (?=...) ) 471 (*pla:...) ) positive lookahead 472 (*positive_lookahead:...) ) 473 474 (?!...) ) 475 (*nla:...) ) negative lookahead 476 (*negative_lookahead:...) ) 477 478 (?<=...) ) 479 (*plb:...) ) positive lookbehind 480 (*positive_lookbehind:...) ) 481 482 (?<!...) ) 483 (*nlb:...) ) negative lookbehind 484 (*negative_lookbehind:...) ) 485</pre> 486Each top-level branch of a lookbehind must have a limit for the number of 487characters it matches. If any branch can match a variable number of characters, 488the maximum for each branch is limited to a value set by the caller of 489<b>pcre2_compile()</b> or defaulted. The default is set when PCRE2 is built 490(ultimate default 255). If every branch matches a fixed number of characters, 491the limit for each branch is 65535 characters. 492</P> 493<br><a name="SEC23" href="#TOC1">NON-ATOMIC LOOKAROUND ASSERTIONS</a><br> 494<P> 495These assertions are specific to PCRE2 and are not Perl-compatible. 496<pre> 497 (?*...) ) 498 (*napla:...) ) synonyms 499 (*non_atomic_positive_lookahead:...) ) 500 501 (?<*...) ) 502 (*naplb:...) ) synonyms 503 (*non_atomic_positive_lookbehind:...) ) 504</PRE> 505</P> 506<br><a name="SEC24" href="#TOC1">SCRIPT RUNS</a><br> 507<P> 508<pre> 509 (*script_run:...) ) script run, can be backtracked into 510 (*sr:...) ) 511 512 (*atomic_script_run:...) ) atomic script run 513 (*asr:...) ) 514</PRE> 515</P> 516<br><a name="SEC25" href="#TOC1">BACKREFERENCES</a><br> 517<P> 518<pre> 519 \n reference by number (can be ambiguous) 520 \gn reference by number 521 \g{n} reference by number 522 \g+n relative reference by number (PCRE2 extension) 523 \g-n relative reference by number 524 \g{+n} relative reference by number (PCRE2 extension) 525 \g{-n} relative reference by number 526 \k<name> reference by name (Perl) 527 \k'name' reference by name (Perl) 528 \g{name} reference by name (Perl) 529 \k{name} reference by name (.NET) 530 (?P=name) reference by name (Python) 531</PRE> 532</P> 533<br><a name="SEC26" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br> 534<P> 535<pre> 536 (?R) recurse whole pattern 537 (?n) call subroutine by absolute number 538 (?+n) call subroutine by relative number 539 (?-n) call subroutine by relative number 540 (?&name) call subroutine by name (Perl) 541 (?P>name) call subroutine by name (Python) 542 \g<name> call subroutine by name (Oniguruma) 543 \g'name' call subroutine by name (Oniguruma) 544 \g<n> call subroutine by absolute number (Oniguruma) 545 \g'n' call subroutine by absolute number (Oniguruma) 546 \g<+n> call subroutine by relative number (PCRE2 extension) 547 \g'+n' call subroutine by relative number (PCRE2 extension) 548 \g<-n> call subroutine by relative number (PCRE2 extension) 549 \g'-n' call subroutine by relative number (PCRE2 extension) 550</PRE> 551</P> 552<br><a name="SEC27" href="#TOC1">CONDITIONAL PATTERNS</a><br> 553<P> 554<pre> 555 (?(condition)yes-pattern) 556 (?(condition)yes-pattern|no-pattern) 557 558 (?(n) absolute reference condition 559 (?(+n) relative reference condition (PCRE2 extension) 560 (?(-n) relative reference condition (PCRE2 extension) 561 (?(<name>) named reference condition (Perl) 562 (?('name') named reference condition (Perl) 563 (?(name) named reference condition (PCRE2, deprecated) 564 (?(R) overall recursion condition 565 (?(Rn) specific numbered group recursion condition 566 (?(R&name) specific named group recursion condition 567 (?(DEFINE) define groups for reference 568 (?(VERSION[>]=n.m) test PCRE2 version 569 (?(assert) assertion condition 570</pre> 571Note the ambiguity of (?(R) and (?(Rn) which might be named reference 572conditions or recursion tests. Such a condition is interpreted as a reference 573condition if the relevant named group exists. 574</P> 575<br><a name="SEC28" href="#TOC1">BACKTRACKING CONTROL</a><br> 576<P> 577All backtracking control verbs may be in the form (*VERB:NAME). For (*MARK) the 578name is mandatory, for the others it is optional. (*SKIP) changes its behaviour 579if :NAME is present. The others just set a name for passing back to the caller, 580but this is not a name that (*SKIP) can see. The following act immediately they 581are reached: 582<pre> 583 (*ACCEPT) force successful match 584 (*FAIL) force backtrack; synonym (*F) 585 (*MARK:NAME) set name to be passed back; synonym (*:NAME) 586</pre> 587The following act only when a subsequent match failure causes a backtrack to 588reach them. They all force a match failure, but they differ in what happens 589afterwards. Those that advance the start-of-match point do so only if the 590pattern is not anchored. 591<pre> 592 (*COMMIT) overall failure, no advance of starting point 593 (*PRUNE) advance to next starting character 594 (*SKIP) advance to current matching position 595 (*SKIP:NAME) advance to position corresponding to an earlier 596 (*MARK:NAME); if not found, the (*SKIP) is ignored 597 (*THEN) local failure, backtrack to next alternation 598</pre> 599The effect of one of these verbs in a group called as a subroutine is confined 600to the subroutine call. 601</P> 602<br><a name="SEC29" href="#TOC1">CALLOUTS</a><br> 603<P> 604<pre> 605 (?C) callout (assumed number 0) 606 (?Cn) callout with numerical data n 607 (?C"text") callout with string data 608</pre> 609The allowed string delimiters are ` ' " ^ % # $ (which are the same for the 610start and the end), and the starting delimiter { matched with the ending 611delimiter }. To encode the ending delimiter within the string, double it. 612</P> 613<br><a name="SEC30" href="#TOC1">SEE ALSO</a><br> 614<P> 615<b>pcre2pattern</b>(3), <b>pcre2api</b>(3), <b>pcre2callout</b>(3), 616<b>pcre2matching</b>(3), <b>pcre2</b>(3). 617</P> 618<br><a name="SEC31" href="#TOC1">AUTHOR</a><br> 619<P> 620Philip Hazel 621<br> 622Retired from University Computing Service 623<br> 624Cambridge, England. 625<br> 626</P> 627<br><a name="SEC32" href="#TOC1">REVISION</a><br> 628<P> 629Last updated: 12 October 2023 630<br> 631Copyright © 1997-2023 University of Cambridge. 632<br> 633<p> 634Return to the <a href="index.html">PCRE2 index page</a>. 635</p> 636