doc/html/pcre2syntax.html - platform/external/pcre - Gitiles

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 <title>pcre2syntax specification</title>
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 <h1>pcre2syntax man page</h1>
 <p>
 Return to the <a href="index.html">PCRE2 index page</a>.
 </p>
 <p>
 This page is part of the PCRE2 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">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a>
 <li><a name="TOC2" href="#SEC2">QUOTING</a>
 <li><a name="TOC3" href="#SEC3">ESCAPED 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">PCRE2 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">REPORTED MATCH POINT SETTING</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">NEWLINE CONVENTION</a>
 <li><a name="TOC18" href="#SEC18">WHAT \R MATCHES</a>
 <li><a name="TOC19" href="#SEC19">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
 <li><a name="TOC20" href="#SEC20">NON-ATOMIC LOOKAROUND ASSERTIONS</a>
 <li><a name="TOC21" href="#SEC21">SCRIPT RUNS</a>
 <li><a name="TOC22" href="#SEC22">BACKREFERENCES</a>
 <li><a name="TOC23" href="#SEC23">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
 <li><a name="TOC24" href="#SEC24">CONDITIONAL PATTERNS</a>
 <li><a name="TOC25" href="#SEC25">BACKTRACKING CONTROL</a>
 <li><a name="TOC26" href="#SEC26">CALLOUTS</a>
 <li><a name="TOC27" href="#SEC27">SEE ALSO</a>
 <li><a name="TOC28" href="#SEC28">AUTHOR</a>
 <li><a name="TOC29" href="#SEC29">REVISION</a>
 </ul>
 <br><a name="SEC1" href="#TOC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
 <P>
 The full syntax and semantics of the regular expressions that are supported by
 PCRE2 are described in the
 <a href="pcre2pattern.html"><b>pcre2pattern</b></a>
 documentation. This document contains 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">ESCAPED CHARACTERS</a><br>
 <P>
 This table applies to ASCII and Unicode environments. An unrecognized escape
 sequence causes an error.
 <pre>
   \a         alarm, that is, the BEL character (hex 07)
   \cx        "control-x", where x is any ASCII printing 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..
   \N{U+hh..} character with Unicode code point hh.. (Unicode mode only)
   \xhh       character with hex code hh
   \x{hh..}   character with hex code hh..
 </pre>
 If PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX is set ("ALT_BSUX mode"), the
 following are also recognized:
 <pre>
   \U         the character "U"
   \uhhhh     character with hex code hhhh
   \u{hh..}   character with hex code hh.. but only for EXTRA_ALT_BSUX
 </pre>
 When \x is not followed by {, from zero to two hexadecimal digits are read,
 but in ALT_BSUX mode \x must be followed by two hexadecimal digits to be
 recognized as a hexadecimal escape; otherwise it matches a literal "x".
 Likewise, if \u (in ALT_BSUX mode) is not followed by four hexadecimal digits
 or (in EXTRA_ALT_BSUX mode) a sequence of hex digits in curly brackets, it
 matches a literal "u".
 </P>
 <P>
 Note that \0dd is always an octal code. The treatment of backslash followed by
 a non-zero digit is complicated; for details see the section
 <a href="pcre2pattern.html#digitsafterbackslash">"Non-printing characters"</a>
 in the
 <a href="pcre2pattern.html"><b>pcre2pattern</b></a>
 documentation, where details of escape processing in EBCDIC environments are
 also given. \N{U+hh..} is synonymous with \x{hh..} in PCRE2 but is not
 supported in EBCDIC environments. Note that \N not followed by an opening
 curly bracket has a different meaning (see below).
 </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 code 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{<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 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>
 \C is dangerous because it may leave the current matching point in the middle
 of a UTF-8 or UTF-16 character. The application can lock out the use of \C by
 setting the PCRE2_NEVER_BACKSLASH_C option. It is also possible to build PCRE2
 with the use of \C permanently disabled.
 </P>
 <P>
 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-specific matching is
 happening, \s and \w may also match characters with code points in the range
 128-255. If the PCRE2_UCP option is set, the behaviour of these escape
 sequences is changed to use Unicode properties and they match many more
 characters.
 </P>
 <br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES 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">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br>
 <P>
 <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, VT, FF, CR
   Xuc        Univerally-named character: one that can be
                represented by a Universal Character Name
   Xwd        Perl word: property Xan or underscore
 </pre>
 Perl and POSIX space are now the same. Perl added VT to its space character set
 at release 5.18.
 </P>
 <br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
 <P>
 Adlam,
 Ahom,
 Anatolian_Hieroglyphs,
 Arabic,
 Armenian,
 Avestan,
 Balinese,
 Bamum,
 Bassa_Vah,
 Batak,
 Bengali,
 Bhaiksuki,
 Bopomofo,
 Brahmi,
 Braille,
 Buginese,
 Buhid,
 Canadian_Aboriginal,
 Carian,
 Caucasian_Albanian,
 Chakma,
 Cham,
 Cherokee,
 Chorasmian,
 Common,
 Coptic,
 Cuneiform,
 Cypriot,
 Cyrillic,
 Deseret,
 Devanagari,
 Dives_Akuru,
 Dogra,
 Duployan,
 Egyptian_Hieroglyphs,
 Elbasan,
 Elymaic,
 Ethiopic,
 Georgian,
 Glagolitic,
 Gothic,
 Grantha,
 Greek,
 Gujarati,
 Gunjala_Gondi,
 Gurmukhi,
 Han,
 Hangul,
 Hanifi_Rohingya,
 Hanunoo,
 Hatran,
 Hebrew,
 Hiragana,
 Imperial_Aramaic,
 Inherited,
 Inscriptional_Pahlavi,
 Inscriptional_Parthian,
 Javanese,
 Kaithi,
 Kannada,
 Katakana,
 Kayah_Li,
 Kharoshthi,
 Khitan_Small_Script,
 Khmer,
 Khojki,
 Khudawadi,
 Lao,
 Latin,
 Lepcha,
 Limbu,
 Linear_A,
 Linear_B,
 Lisu,
 Lycian,
 Lydian,
 Mahajani,
 Makasar,
 Malayalam,
 Mandaic,
 Manichaean,
 Marchen,
 Masaram_Gondi,
 Medefaidrin,
 Meetei_Mayek,
 Mende_Kikakui,
 Meroitic_Cursive,
 Meroitic_Hieroglyphs,
 Miao,
 Modi,
 Mongolian,
 Mro,
 Multani,
 Myanmar,
 Nabataean,
 Nandinagari,
 New_Tai_Lue,
 Newa,
 Nko,
 Nushu,
 Nyakeng_Puachue_Hmong,
 Ogham,
 Ol_Chiki,
 Old_Hungarian,
 Old_Italic,
 Old_North_Arabian,
 Old_Permic,
 Old_Persian,
 Old_Sogdian,
 Old_South_Arabian,
 Old_Turkic,
 Oriya,
 Osage,
 Osmanya,
 Pahawh_Hmong,
 Palmyrene,
 Pau_Cin_Hau,
 Phags_Pa,
 Phoenician,
 Psalter_Pahlavi,
 Rejang,
 Runic,
 Samaritan,
 Saurashtra,
 Sharada,
 Shavian,
 Siddham,
 SignWriting,
 Sinhala,
 Sogdian,
 Sora_Sompeng,
 Soyombo,
 Sundanese,
 Syloti_Nagri,
 Syriac,
 Tagalog,
 Tagbanwa,
 Tai_Le,
 Tai_Tham,
 Tai_Viet,
 Takri,
 Tamil,
 Tangut,
 Telugu,
 Thaana,
 Thai,
 Tibetan,
 Tifinagh,
 Tirhuta,
 Ugaritic,
 Vai,
 Wancho,
 Warang_Citi,
 Yezidi,
 Yi,
 Zanabazar_Square.
 </P>
 <br><a name="SEC8" 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       white space
   upper       upper case letter
   word        same as \w
   xdigit      hexadecimal digit
 </pre>
 In PCRE2, POSIX character set names recognize only ASCII characters by default,
 but some of them use Unicode properties if PCRE2_UCP is set. You can use
 \Q...\E inside a character class.
 </P>
 <br><a name="SEC9" 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="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
 <P>
 <pre>
   \b          word boundary
   \B          not a word boundary
   ^           start of subject
                 also after an internal newline in multiline mode
                 (after any newline if PCRE2_ALT_CIRCUMFLEX is set)
   \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="SEC11" href="#TOC1">REPORTED MATCH POINT SETTING</a><br>
 <P>
 <pre>
   \K          set reported start of match
 </pre>
 From release 10.38 \K is not permitted by default in lookaround assertions,
 for compatibility with Perl. However, if the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
 option is set, the previous behaviour is re-enabled. When this option is set,
 \K is honoured in positive assertions, but ignored in negative ones.
 </P>
 <br><a name="SEC12" href="#TOC1">ALTERNATION</a><br>
 <P>
 <pre>
   expr|expr|expr...
 </PRE>
 </P>
 <br><a name="SEC13" href="#TOC1">CAPTURING</a><br>
 <P>
 <pre>
   (...)           capture group
   (?&#60;name&#62;...)    named capture group (Perl)
   (?'name'...)    named capture group (Perl)
   (?P&#60;name&#62;...)   named capture group (Python)
   (?:...)         non-capture group
   (?|...)         non-capture group; reset group numbers for
                    capture groups in each alternative
 </pre>
 In non-UTF modes, names may contain underscores and ASCII letters and digits;
 in UTF modes, any Unicode letters and Unicode decimal digits are permitted. In
 both cases, a name must not start with a digit.
 </P>
 <br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br>
 <P>
 <pre>
   (?&#62;...)         atomic non-capture group
   (*atomic:...)   atomic non-capture group
 </PRE>
 </P>
 <br><a name="SEC15" href="#TOC1">COMMENT</a><br>
 <P>
 <pre>
   (?#....)        comment (not nestable)
 </PRE>
 </P>
 <br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br>
 <P>
 Changes of these options within a group are automatically cancelled at the end
 of the group.
 <pre>
   (?i)            caseless
   (?J)            allow duplicate named groups
   (?m)            multiline
   (?n)            no auto capture
   (?s)            single line (dotall)
   (?U)            default ungreedy (lazy)
   (?x)            extended: ignore white space except in classes
   (?xx)           as (?x) but also ignore space and tab in classes
   (?-...)         unset option(s)
   (?^)            unset imnsx options
 </pre>
 Unsetting x or xx unsets both. Several options may be set at once, and a
 mixture of setting and unsetting such as (?i-x) is allowed, but there may be
 only one hyphen. Setting (but no unsetting) is allowed after (?^ for example
 (?^in). An option setting may appear at the start of a non-capture group, for
 example (?i:...).
 </P>
 <P>
 The following are recognized only at the very start of a pattern or after one
 of the newline or \R options with similar syntax. More than one of them may
 appear. For the first three, d is a decimal number.
 <pre>
   (*LIMIT_DEPTH=d) set the backtracking limit to d
   (*LIMIT_HEAP=d)  set the heap size limit to d * 1024 bytes
   (*LIMIT_MATCH=d) set the match limit to d
   (*NOTEMPTY)      set PCRE2_NOTEMPTY when matching
   (*NOTEMPTY_ATSTART) set PCRE2_NOTEMPTY_ATSTART when matching
   (*NO_AUTO_POSSESS) no auto-possessification (PCRE2_NO_AUTO_POSSESS)
   (*NO_DOTSTAR_ANCHOR) no .* anchoring (PCRE2_NO_DOTSTAR_ANCHOR)
   (*NO_JIT)       disable JIT optimization
   (*NO_START_OPT) no start-match optimization (PCRE2_NO_START_OPTIMIZE)
   (*UTF)          set appropriate UTF mode for the library in use
   (*UCP)          set PCRE2_UCP (use Unicode properties for \d etc)
 </pre>
 Note that LIMIT_DEPTH, LIMIT_HEAP, and LIMIT_MATCH can only reduce the value of
 the limits set by the caller of <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b>,
 not increase them. LIMIT_RECURSION is an obsolete synonym for LIMIT_DEPTH. The
 application can lock out the use of (*UTF) and (*UCP) by setting the
 PCRE2_NEVER_UTF or PCRE2_NEVER_UCP options, respectively, at compile time.
 </P>
 <br><a name="SEC17" href="#TOC1">NEWLINE CONVENTION</a><br>
 <P>
 These are recognized only at the very start of the pattern or after option
 settings with a similar syntax.
 <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
   (*NUL)          the NUL character (binary zero)
 </PRE>
 </P>
 <br><a name="SEC18" href="#TOC1">WHAT \R MATCHES</a><br>
 <P>
 These are recognized only at the very start of the pattern or after option
 setting with a similar syntax.
 <pre>
   (*BSR_ANYCRLF)  CR, LF, or CRLF
   (*BSR_UNICODE)  any Unicode newline sequence
 </PRE>
 </P>
 <br><a name="SEC19" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
 <P>
 <pre>
   (?=...)                     )
   (*pla:...)                  ) positive lookahead
   (*positive_lookahead:...)   )

   (?!...)                     )
   (*nla:...)                  ) negative lookahead
   (*negative_lookahead:...)   )

   (?&#60;=...)                    )
   (*plb:...)                  ) positive lookbehind
   (*positive_lookbehind:...)  )

   (?&#60;!...)                    )
   (*nlb:...)                  ) negative lookbehind
   (*negative_lookbehind:...)  )
 </pre>
 Each top-level branch of a lookbehind must be of a fixed length.
 </P>
 <br><a name="SEC20" href="#TOC1">NON-ATOMIC LOOKAROUND ASSERTIONS</a><br>
 <P>
 These assertions are specific to PCRE2 and are not Perl-compatible.
 <pre>
   (?*...)                                )
   (*napla:...)                           ) synonyms
   (*non_atomic_positive_lookahead:...)   )

   (?&#60;*...)                               )
   (*naplb:...)                           ) synonyms
   (*non_atomic_positive_lookbehind:...)  )
 </PRE>
 </P>
 <br><a name="SEC21" href="#TOC1">SCRIPT RUNS</a><br>
 <P>
 <pre>
   (*script_run:...)           ) script run, can be backtracked into
   (*sr:...)                   )

   (*atomic_script_run:...)    ) atomic script run
   (*asr:...)                  )
 </PRE>
 </P>
 <br><a name="SEC22" 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 (PCRE2 extension)
   \g-n            relative reference by number
   \g{+n}          relative reference by number (PCRE2 extension)
   \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="SEC23" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
 <P>
 <pre>
   (?R)            recurse whole pattern
   (?n)            call subroutine by absolute number
   (?+n)           call subroutine by relative number
   (?-n)           call subroutine by relative number
   (?&name)        call subroutine by name (Perl)
   (?P&#62;name)       call subroutine by name (Python)
   \g&#60;name&#62;        call subroutine by name (Oniguruma)
   \g'name'        call subroutine by name (Oniguruma)
   \g&#60;n&#62;           call subroutine by absolute number (Oniguruma)
   \g'n'           call subroutine by absolute number (Oniguruma)
   \g&#60;+n&#62;          call subroutine by relative number (PCRE2 extension)
   \g'+n'          call subroutine by relative number (PCRE2 extension)
   \g&#60;-n&#62;          call subroutine by relative number (PCRE2 extension)
   \g'-n'          call subroutine by relative number (PCRE2 extension)
 </PRE>
 </P>
 <br><a name="SEC24" 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 (PCRE2, deprecated)
   (?(R)               overall recursion condition
   (?(Rn)              specific numbered group recursion condition
   (?(R&name)          specific named group recursion condition
   (?(DEFINE)          define groups for reference
   (?(VERSION[&#62;]=n.m)  test PCRE2 version
   (?(assert)          assertion condition
 </pre>
 Note the ambiguity of (?(R) and (?(Rn) which might be named reference
 conditions or recursion tests. Such a condition is interpreted as a reference
 condition if the relevant named group exists.
 </P>
 <br><a name="SEC25" href="#TOC1">BACKTRACKING CONTROL</a><br>
 <P>
 All backtracking control verbs may be in the form (*VERB:NAME). For (*MARK) the
 name is mandatory, for the others it is optional. (*SKIP) changes its behaviour
 if :NAME is present. The others just set a name for passing back to the caller,
 but this is not a name that (*SKIP) can see. 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
   (*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
 </pre>
 The effect of one of these verbs in a group called as a subroutine is confined
 to the subroutine call.
 </P>
 <br><a name="SEC26" href="#TOC1">CALLOUTS</a><br>
 <P>
 <pre>
   (?C)            callout (assumed number 0)
   (?Cn)           callout with numerical data n
   (?C"text")      callout with string data
 </pre>
 The allowed string delimiters are ` ' " ^ % # $ (which are the same for the
 start and the end), and the starting delimiter { matched with the ending
 delimiter }. To encode the ending delimiter within the string, double it.
 </P>
 <br><a name="SEC27" href="#TOC1">SEE ALSO</a><br>
 <P>
 <b>pcre2pattern</b>(3), <b>pcre2api</b>(3), <b>pcre2callout</b>(3),
 <b>pcre2matching</b>(3), <b>pcre2</b>(3).
 </P>
 <br><a name="SEC28" href="#TOC1">AUTHOR</a><br>
 <P>
 Philip Hazel
 <br>
 Retired from University Computing Service
 <br>
 Cambridge, England.
 <br>
 </P>
 <br><a name="SEC29" href="#TOC1">REVISION</a><br>
 <P>
 Last updated: 30 August 2021
 <br>
 Copyright &copy; 1997-2021 University of Cambridge.
 <br>
 <p>
 Return to the <a href="index.html">PCRE2 index page</a>.
 </p>
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	<title>pcre2syntax specification</title>
	</head>
	<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
	<h1>pcre2syntax man page</h1>
	<p>
	Return to the <a href="index.html">PCRE2 index page</a>.
	</p>
	<p>
	This page is part of the PCRE2 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">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a>
	<li><a name="TOC2" href="#SEC2">QUOTING</a>
	<li><a name="TOC3" href="#SEC3">ESCAPED 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">PCRE2 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">REPORTED MATCH POINT SETTING</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">NEWLINE CONVENTION</a>
	<li><a name="TOC18" href="#SEC18">WHAT \R MATCHES</a>
	<li><a name="TOC19" href="#SEC19">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
	<li><a name="TOC20" href="#SEC20">NON-ATOMIC LOOKAROUND ASSERTIONS</a>
	<li><a name="TOC21" href="#SEC21">SCRIPT RUNS</a>
	<li><a name="TOC22" href="#SEC22">BACKREFERENCES</a>
	<li><a name="TOC23" href="#SEC23">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
	<li><a name="TOC24" href="#SEC24">CONDITIONAL PATTERNS</a>
	<li><a name="TOC25" href="#SEC25">BACKTRACKING CONTROL</a>
	<li><a name="TOC26" href="#SEC26">CALLOUTS</a>
	<li><a name="TOC27" href="#SEC27">SEE ALSO</a>
	<li><a name="TOC28" href="#SEC28">AUTHOR</a>
	<li><a name="TOC29" href="#SEC29">REVISION</a>
	</ul>
	<br><a name="SEC1" href="#TOC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
	<P>
	The full syntax and semantics of the regular expressions that are supported by
	PCRE2 are described in the
	<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
	documentation. This document contains 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">ESCAPED CHARACTERS</a><br>
	<P>
	This table applies to ASCII and Unicode environments. An unrecognized escape
	sequence causes an error.
	<pre>
	\a alarm, that is, the BEL character (hex 07)
	\cx "control-x", where x is any ASCII printing 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..
	\N{U+hh..} character with Unicode code point hh.. (Unicode mode only)
	\xhh character with hex code hh
	\x{hh..} character with hex code hh..
	</pre>
	If PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX is set ("ALT_BSUX mode"), the
	following are also recognized:
	<pre>
	\U the character "U"
	\uhhhh character with hex code hhhh
	\u{hh..} character with hex code hh.. but only for EXTRA_ALT_BSUX
	</pre>
	When \x is not followed by {, from zero to two hexadecimal digits are read,
	but in ALT_BSUX mode \x must be followed by two hexadecimal digits to be
	recognized as a hexadecimal escape; otherwise it matches a literal "x".
	Likewise, if \u (in ALT_BSUX mode) is not followed by four hexadecimal digits
	or (in EXTRA_ALT_BSUX mode) a sequence of hex digits in curly brackets, it
	matches a literal "u".
	</P>
	<P>
	Note that \0dd is always an octal code. The treatment of backslash followed by
	a non-zero digit is complicated; for details see the section
	<a href="pcre2pattern.html#digitsafterbackslash">"Non-printing characters"</a>
	in the
	<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
	documentation, where details of escape processing in EBCDIC environments are
	also given. \N{U+hh..} is synonymous with \x{hh..} in PCRE2 but is not
	supported in EBCDIC environments. Note that \N not followed by an opening
	curly bracket has a different meaning (see below).
	</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 code 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{<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 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>
	\C is dangerous because it may leave the current matching point in the middle
	of a UTF-8 or UTF-16 character. The application can lock out the use of \C by
	setting the PCRE2_NEVER_BACKSLASH_C option. It is also possible to build PCRE2
	with the use of \C permanently disabled.
	</P>
	<P>
	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-specific matching is
	happening, \s and \w may also match characters with code points in the range
	128-255. If the PCRE2_UCP option is set, the behaviour of these escape
	sequences is changed to use Unicode properties and they match many more
	characters.
	</P>
	<br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES 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">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br>
	<P>
	<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, VT, FF, CR
	Xuc Univerally-named character: one that can be
	represented by a Universal Character Name
	Xwd Perl word: property Xan or underscore
	</pre>
	Perl and POSIX space are now the same. Perl added VT to its space character set
	at release 5.18.
	</P>
	<br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
	<P>
	Adlam,
	Ahom,
	Anatolian_Hieroglyphs,
	Arabic,
	Armenian,
	Avestan,
	Balinese,
	Bamum,
	Bassa_Vah,
	Batak,
	Bengali,
	Bhaiksuki,
	Bopomofo,
	Brahmi,
	Braille,
	Buginese,
	Buhid,
	Canadian_Aboriginal,
	Carian,
	Caucasian_Albanian,
	Chakma,
	Cham,
	Cherokee,
	Chorasmian,
	Common,
	Coptic,
	Cuneiform,
	Cypriot,
	Cyrillic,
	Deseret,
	Devanagari,
	Dives_Akuru,
	Dogra,
	Duployan,
	Egyptian_Hieroglyphs,
	Elbasan,
	Elymaic,
	Ethiopic,
	Georgian,
	Glagolitic,
	Gothic,
	Grantha,
	Greek,
	Gujarati,
	Gunjala_Gondi,
	Gurmukhi,
	Han,
	Hangul,
	Hanifi_Rohingya,
	Hanunoo,
	Hatran,
	Hebrew,
	Hiragana,
	Imperial_Aramaic,
	Inherited,
	Inscriptional_Pahlavi,
	Inscriptional_Parthian,
	Javanese,
	Kaithi,
	Kannada,
	Katakana,
	Kayah_Li,
	Kharoshthi,
	Khitan_Small_Script,
	Khmer,
	Khojki,
	Khudawadi,
	Lao,
	Latin,
	Lepcha,
	Limbu,
	Linear_A,
	Linear_B,
	Lisu,
	Lycian,
	Lydian,
	Mahajani,
	Makasar,
	Malayalam,
	Mandaic,
	Manichaean,
	Marchen,
	Masaram_Gondi,
	Medefaidrin,
	Meetei_Mayek,
	Mende_Kikakui,
	Meroitic_Cursive,
	Meroitic_Hieroglyphs,
	Miao,
	Modi,
	Mongolian,
	Mro,
	Multani,
	Myanmar,
	Nabataean,
	Nandinagari,
	New_Tai_Lue,
	Newa,
	Nko,
	Nushu,
	Nyakeng_Puachue_Hmong,
	Ogham,
	Ol_Chiki,
	Old_Hungarian,
	Old_Italic,
	Old_North_Arabian,
	Old_Permic,
	Old_Persian,
	Old_Sogdian,
	Old_South_Arabian,
	Old_Turkic,
	Oriya,
	Osage,
	Osmanya,
	Pahawh_Hmong,
	Palmyrene,
	Pau_Cin_Hau,
	Phags_Pa,
	Phoenician,
	Psalter_Pahlavi,
	Rejang,
	Runic,
	Samaritan,
	Saurashtra,
	Sharada,
	Shavian,
	Siddham,
	SignWriting,
	Sinhala,
	Sogdian,
	Sora_Sompeng,
	Soyombo,
	Sundanese,
	Syloti_Nagri,
	Syriac,
	Tagalog,
	Tagbanwa,
	Tai_Le,
	Tai_Tham,
	Tai_Viet,
	Takri,
	Tamil,
	Tangut,
	Telugu,
	Thaana,
	Thai,
	Tibetan,
	Tifinagh,
	Tirhuta,
	Ugaritic,
	Vai,
	Wancho,
	Warang_Citi,
	Yezidi,
	Yi,
	Zanabazar_Square.
	</P>
	<br><a name="SEC8" 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 white space
	upper upper case letter
	word same as \w
	xdigit hexadecimal digit
	</pre>
	In PCRE2, POSIX character set names recognize only ASCII characters by default,
	but some of them use Unicode properties if PCRE2_UCP is set. You can use
	\Q...\E inside a character class.
	</P>
	<br><a name="SEC9" 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="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
	<P>
	<pre>
	\b word boundary
	\B not a word boundary
	^ start of subject
	also after an internal newline in multiline mode
	(after any newline if PCRE2_ALT_CIRCUMFLEX is set)
	\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="SEC11" href="#TOC1">REPORTED MATCH POINT SETTING</a><br>
	<P>
	<pre>
	\K set reported start of match
	</pre>
	From release 10.38 \K is not permitted by default in lookaround assertions,
	for compatibility with Perl. However, if the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
	option is set, the previous behaviour is re-enabled. When this option is set,
	\K is honoured in positive assertions, but ignored in negative ones.
	</P>
	<br><a name="SEC12" href="#TOC1">ALTERNATION</a><br>
	<P>
	<pre>
	expr\|expr\|expr...
	</PRE>
	</P>
	<br><a name="SEC13" href="#TOC1">CAPTURING</a><br>
	<P>
	<pre>
	(...) capture group
	(?<name>...) named capture group (Perl)
	(?'name'...) named capture group (Perl)
	(?P<name>...) named capture group (Python)
	(?:...) non-capture group
	(?\|...) non-capture group; reset group numbers for
	capture groups in each alternative
	</pre>
	In non-UTF modes, names may contain underscores and ASCII letters and digits;
	in UTF modes, any Unicode letters and Unicode decimal digits are permitted. In
	both cases, a name must not start with a digit.
	</P>
	<br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br>
	<P>
	<pre>
	(?>...) atomic non-capture group
	(*atomic:...) atomic non-capture group
	</PRE>
	</P>
	<br><a name="SEC15" href="#TOC1">COMMENT</a><br>
	<P>
	<pre>
	(?#....) comment (not nestable)
	</PRE>
	</P>
	<br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br>
	<P>
	Changes of these options within a group are automatically cancelled at the end
	of the group.
	<pre>
	(?i) caseless
	(?J) allow duplicate named groups
	(?m) multiline
	(?n) no auto capture
	(?s) single line (dotall)
	(?U) default ungreedy (lazy)
	(?x) extended: ignore white space except in classes
	(?xx) as (?x) but also ignore space and tab in classes
	(?-...) unset option(s)
	(?^) unset imnsx options
	</pre>
	Unsetting x or xx unsets both. Several options may be set at once, and a
	mixture of setting and unsetting such as (?i-x) is allowed, but there may be
	only one hyphen. Setting (but no unsetting) is allowed after (?^ for example
	(?^in). An option setting may appear at the start of a non-capture group, for
	example (?i:...).
	</P>
	<P>
	The following are recognized only at the very start of a pattern or after one
	of the newline or \R options with similar syntax. More than one of them may
	appear. For the first three, d is a decimal number.
	<pre>
	(*LIMIT_DEPTH=d) set the backtracking limit to d
	(LIMIT_HEAP=d) set the heap size limit to d 1024 bytes
	(*LIMIT_MATCH=d) set the match limit to d
	(*NOTEMPTY) set PCRE2_NOTEMPTY when matching
	(*NOTEMPTY_ATSTART) set PCRE2_NOTEMPTY_ATSTART when matching
	(*NO_AUTO_POSSESS) no auto-possessification (PCRE2_NO_AUTO_POSSESS)
	(NO_DOTSTAR_ANCHOR) no . anchoring (PCRE2_NO_DOTSTAR_ANCHOR)
	(*NO_JIT) disable JIT optimization
	(*NO_START_OPT) no start-match optimization (PCRE2_NO_START_OPTIMIZE)
	(*UTF) set appropriate UTF mode for the library in use
	(*UCP) set PCRE2_UCP (use Unicode properties for \d etc)
	</pre>
	Note that LIMIT_DEPTH, LIMIT_HEAP, and LIMIT_MATCH can only reduce the value of
	the limits set by the caller of <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b>,
	not increase them. LIMIT_RECURSION is an obsolete synonym for LIMIT_DEPTH. The
	application can lock out the use of (UTF) and (UCP) by setting the
	PCRE2_NEVER_UTF or PCRE2_NEVER_UCP options, respectively, at compile time.
	</P>
	<br><a name="SEC17" href="#TOC1">NEWLINE CONVENTION</a><br>
	<P>
	These are recognized only at the very start of the pattern or after option
	settings with a similar syntax.
	<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
	(*NUL) the NUL character (binary zero)
	</PRE>
	</P>
	<br><a name="SEC18" href="#TOC1">WHAT \R MATCHES</a><br>
	<P>
	These are recognized only at the very start of the pattern or after option
	setting with a similar syntax.
	<pre>
	(*BSR_ANYCRLF) CR, LF, or CRLF
	(*BSR_UNICODE) any Unicode newline sequence
	</PRE>
	</P>
	<br><a name="SEC19" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
	<P>
	<pre>
	(?=...) )
	(*pla:...) ) positive lookahead
	(*positive_lookahead:...) )

	(?!...) )
	(*nla:...) ) negative lookahead
	(*negative_lookahead:...) )

	(?<=...) )
	(*plb:...) ) positive lookbehind
	(*positive_lookbehind:...) )

	(?<!...) )
	(*nlb:...) ) negative lookbehind
	(*negative_lookbehind:...) )
	</pre>
	Each top-level branch of a lookbehind must be of a fixed length.
	</P>
	<br><a name="SEC20" href="#TOC1">NON-ATOMIC LOOKAROUND ASSERTIONS</a><br>
	<P>
	These assertions are specific to PCRE2 and are not Perl-compatible.
	<pre>
	(?*...) )
	(*napla:...) ) synonyms
	(*non_atomic_positive_lookahead:...) )

	(?<*...) )
	(*naplb:...) ) synonyms
	(*non_atomic_positive_lookbehind:...) )
	</PRE>
	</P>
	<br><a name="SEC21" href="#TOC1">SCRIPT RUNS</a><br>
	<P>
	<pre>
	(*script_run:...) ) script run, can be backtracked into
	(*sr:...) )

	(*atomic_script_run:...) ) atomic script run
	(*asr:...) )
	</PRE>
	</P>
	<br><a name="SEC22" 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 (PCRE2 extension)
	\g-n relative reference by number
	\g{+n} relative reference by number (PCRE2 extension)
	\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)
	</PRE>
	</P>
	<br><a name="SEC23" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
	<P>
	<pre>
	(?R) recurse whole pattern
	(?n) call subroutine by absolute number
	(?+n) call subroutine by relative number
	(?-n) call subroutine by relative number
	(?&name) call subroutine by name (Perl)
	(?P>name) call subroutine by name (Python)
	\g<name> call subroutine by name (Oniguruma)
	\g'name' call subroutine by name (Oniguruma)
	\g<n> call subroutine by absolute number (Oniguruma)
	\g'n' call subroutine by absolute number (Oniguruma)
	\g<+n> call subroutine by relative number (PCRE2 extension)
	\g'+n' call subroutine by relative number (PCRE2 extension)
	\g<-n> call subroutine by relative number (PCRE2 extension)
	\g'-n' call subroutine by relative number (PCRE2 extension)
	</PRE>
	</P>
	<br><a name="SEC24" 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
	(?(<name>) named reference condition (Perl)
	(?('name') named reference condition (Perl)
	(?(name) named reference condition (PCRE2, deprecated)
	(?(R) overall recursion condition
	(?(Rn) specific numbered group recursion condition
	(?(R&name) specific named group recursion condition
	(?(DEFINE) define groups for reference
	(?(VERSION[>]=n.m) test PCRE2 version
	(?(assert) assertion condition
	</pre>
	Note the ambiguity of (?(R) and (?(Rn) which might be named reference
	conditions or recursion tests. Such a condition is interpreted as a reference
	condition if the relevant named group exists.
	</P>
	<br><a name="SEC25" href="#TOC1">BACKTRACKING CONTROL</a><br>
	<P>
	All backtracking control verbs may be in the form (VERB:NAME). For (MARK) the
	name is mandatory, for the others it is optional. (*SKIP) changes its behaviour
	if :NAME is present. The others just set a name for passing back to the caller,
	but this is not a name that (*SKIP) can see. 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
	(*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
	</pre>
	The effect of one of these verbs in a group called as a subroutine is confined
	to the subroutine call.
	</P>
	<br><a name="SEC26" href="#TOC1">CALLOUTS</a><br>
	<P>
	<pre>
	(?C) callout (assumed number 0)
	(?Cn) callout with numerical data n
	(?C"text") callout with string data
	</pre>
	The allowed string delimiters are ` ' " ^ % # $ (which are the same for the
	start and the end), and the starting delimiter { matched with the ending
	delimiter }. To encode the ending delimiter within the string, double it.
	</P>
	<br><a name="SEC27" href="#TOC1">SEE ALSO</a><br>
	<P>
	<b>pcre2pattern</b>(3), <b>pcre2api</b>(3), <b>pcre2callout</b>(3),
	<b>pcre2matching</b>(3), <b>pcre2</b>(3).
	</P>
	<br><a name="SEC28" href="#TOC1">AUTHOR</a><br>
	<P>
	Philip Hazel
	<br>
	Retired from University Computing Service
	<br>
	Cambridge, England.
	<br>
	</P>
	<br><a name="SEC29" href="#TOC1">REVISION</a><br>
	<P>
	Last updated: 30 August 2021
	<br>
	Copyright © 1997-2021 University of Cambridge.
	<br>
	<p>
	Return to the <a href="index.html">PCRE2 index page</a>.
	</p>