608 lines
19 KiB
HTML
608 lines
19 KiB
HTML
<html>
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<head>
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<title>pcre2syntax specification</title>
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</head>
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<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
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<h1>pcre2syntax man page</h1>
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<p>
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Return to the <a href="index.html">PCRE2 index page</a>.
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</p>
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<p>
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This page is part of the PCRE2 HTML documentation. It was generated
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automatically from the original man page. If there is any nonsense in it,
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please consult the man page, in case the conversion went wrong.
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<br>
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<ul>
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<li><a name="TOC1" href="#SEC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a>
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<li><a name="TOC2" href="#SEC2">QUOTING</a>
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<li><a name="TOC3" href="#SEC3">ESCAPED CHARACTERS</a>
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<li><a name="TOC4" href="#SEC4">CHARACTER TYPES</a>
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<li><a name="TOC5" href="#SEC5">GENERAL CATEGORY PROPERTIES FOR \p and \P</a>
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<li><a name="TOC6" href="#SEC6">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a>
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<li><a name="TOC7" href="#SEC7">SCRIPT NAMES FOR \p AND \P</a>
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<li><a name="TOC8" href="#SEC8">CHARACTER CLASSES</a>
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<li><a name="TOC9" href="#SEC9">QUANTIFIERS</a>
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<li><a name="TOC10" href="#SEC10">ANCHORS AND SIMPLE ASSERTIONS</a>
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<li><a name="TOC11" href="#SEC11">MATCH POINT RESET</a>
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<li><a name="TOC12" href="#SEC12">ALTERNATION</a>
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<li><a name="TOC13" href="#SEC13">CAPTURING</a>
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<li><a name="TOC14" href="#SEC14">ATOMIC GROUPS</a>
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<li><a name="TOC15" href="#SEC15">COMMENT</a>
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<li><a name="TOC16" href="#SEC16">OPTION SETTING</a>
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<li><a name="TOC17" href="#SEC17">NEWLINE CONVENTION</a>
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<li><a name="TOC18" href="#SEC18">WHAT \R MATCHES</a>
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<li><a name="TOC19" href="#SEC19">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a>
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<li><a name="TOC20" href="#SEC20">BACKREFERENCES</a>
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<li><a name="TOC21" href="#SEC21">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a>
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<li><a name="TOC22" href="#SEC22">CONDITIONAL PATTERNS</a>
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<li><a name="TOC23" href="#SEC23">BACKTRACKING CONTROL</a>
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<li><a name="TOC24" href="#SEC24">CALLOUTS</a>
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<li><a name="TOC25" href="#SEC25">SEE ALSO</a>
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<li><a name="TOC26" href="#SEC26">AUTHOR</a>
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<li><a name="TOC27" href="#SEC27">REVISION</a>
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</ul>
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<br><a name="SEC1" href="#TOC1">PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY</a><br>
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<P>
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The full syntax and semantics of the regular expressions that are supported by
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PCRE2 are described in the
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<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
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documentation. This document contains a quick-reference summary of the syntax.
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</P>
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<br><a name="SEC2" href="#TOC1">QUOTING</a><br>
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<P>
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<pre>
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\x where x is non-alphanumeric is a literal x
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\Q...\E treat enclosed characters as literal
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</PRE>
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</P>
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<br><a name="SEC3" href="#TOC1">ESCAPED CHARACTERS</a><br>
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<P>
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This table applies to ASCII and Unicode environments.
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<pre>
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\a alarm, that is, the BEL character (hex 07)
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\cx "control-x", where x is any ASCII printing character
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\e escape (hex 1B)
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\f form feed (hex 0C)
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\n newline (hex 0A)
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\r carriage return (hex 0D)
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\t tab (hex 09)
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\0dd character with octal code 0dd
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\ddd character with octal code ddd, or backreference
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\o{ddd..} character with octal code ddd..
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\U "U" if PCRE2_ALT_BSUX is set (otherwise is an error)
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\uhhhh character with hex code hhhh (if PCRE2_ALT_BSUX is set)
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\xhh character with hex code hh
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\x{hhh..} character with hex code hhh..
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</pre>
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Note that \0dd is always an octal code. The treatment of backslash followed by
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a non-zero digit is complicated; for details see the section
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<a href="pcre2pattern.html#digitsafterbackslash">"Non-printing characters"</a>
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in the
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<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
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documentation, where details of escape processing in EBCDIC environments are
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also given.
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</P>
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<P>
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When \x is not followed by {, from zero to two hexadecimal digits are read,
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but if PCRE2_ALT_BSUX is set, \x must be followed by two hexadecimal digits to
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be recognized as a hexadecimal escape; otherwise it matches a literal "x".
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Likewise, if \u (in ALT_BSUX mode) is not followed by four hexadecimal digits,
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it matches a literal "u".
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</P>
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<br><a name="SEC4" href="#TOC1">CHARACTER TYPES</a><br>
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<P>
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<pre>
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. any character except newline;
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in dotall mode, any character whatsoever
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\C one code unit, even in UTF mode (best avoided)
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\d a decimal digit
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\D a character that is not a decimal digit
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\h a horizontal white space character
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\H a character that is not a horizontal white space character
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\N a character that is not a newline
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\p{<i>xx</i>} a character with the <i>xx</i> property
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\P{<i>xx</i>} a character without the <i>xx</i> property
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\R a newline sequence
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\s a white space character
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\S a character that is not a white space character
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\v a vertical white space character
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\V a character that is not a vertical white space character
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\w a "word" character
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\W a "non-word" character
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\X a Unicode extended grapheme cluster
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</pre>
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\C is dangerous because it may leave the current matching point in the middle
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of a UTF-8 or UTF-16 character. The application can lock out the use of \C by
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setting the PCRE2_NEVER_BACKSLASH_C option. It is also possible to build PCRE2
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with the use of \C permanently disabled.
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</P>
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<P>
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By default, \d, \s, and \w match only ASCII characters, even in UTF-8 mode
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or in the 16-bit and 32-bit libraries. However, if locale-specific matching is
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happening, \s and \w may also match characters with code points in the range
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128-255. If the PCRE2_UCP option is set, the behaviour of these escape
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sequences is changed to use Unicode properties and they match many more
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characters.
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</P>
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<br><a name="SEC5" href="#TOC1">GENERAL CATEGORY PROPERTIES FOR \p and \P</a><br>
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<P>
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<pre>
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C Other
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Cc Control
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Cf Format
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Cn Unassigned
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Co Private use
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Cs Surrogate
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L Letter
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Ll Lower case letter
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Lm Modifier letter
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Lo Other letter
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Lt Title case letter
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Lu Upper case letter
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L& Ll, Lu, or Lt
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M Mark
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Mc Spacing mark
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Me Enclosing mark
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Mn Non-spacing mark
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N Number
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Nd Decimal number
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Nl Letter number
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No Other number
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P Punctuation
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Pc Connector punctuation
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Pd Dash punctuation
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Pe Close punctuation
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Pf Final punctuation
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Pi Initial punctuation
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Po Other punctuation
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Ps Open punctuation
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S Symbol
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Sc Currency symbol
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Sk Modifier symbol
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Sm Mathematical symbol
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So Other symbol
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Z Separator
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Zl Line separator
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Zp Paragraph separator
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Zs Space separator
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</PRE>
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</P>
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<br><a name="SEC6" href="#TOC1">PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P</a><br>
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<P>
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<pre>
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Xan Alphanumeric: union of properties L and N
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Xps POSIX space: property Z or tab, NL, VT, FF, CR
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Xsp Perl space: property Z or tab, NL, VT, FF, CR
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Xuc Univerally-named character: one that can be
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represented by a Universal Character Name
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Xwd Perl word: property Xan or underscore
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</pre>
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Perl and POSIX space are now the same. Perl added VT to its space character set
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at release 5.18.
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</P>
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<br><a name="SEC7" href="#TOC1">SCRIPT NAMES FOR \p AND \P</a><br>
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<P>
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Ahom,
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Anatolian_Hieroglyphs,
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Arabic,
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Armenian,
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Avestan,
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Balinese,
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Bamum,
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Bassa_Vah,
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Batak,
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Bengali,
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Bopomofo,
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Brahmi,
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Braille,
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Buginese,
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Buhid,
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Canadian_Aboriginal,
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Carian,
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Caucasian_Albanian,
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Chakma,
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Cham,
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Cherokee,
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Common,
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Coptic,
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Cuneiform,
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Cypriot,
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Cyrillic,
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Deseret,
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Devanagari,
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Duployan,
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Egyptian_Hieroglyphs,
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Elbasan,
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Ethiopic,
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Georgian,
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Glagolitic,
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Gothic,
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Grantha,
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Greek,
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Gujarati,
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Gurmukhi,
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Han,
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Hangul,
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Hanunoo,
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Hatran,
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Hebrew,
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Hiragana,
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Imperial_Aramaic,
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Inherited,
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Inscriptional_Pahlavi,
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Inscriptional_Parthian,
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Javanese,
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Kaithi,
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Kannada,
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Katakana,
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Kayah_Li,
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Kharoshthi,
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Khmer,
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Khojki,
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Khudawadi,
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Lao,
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Latin,
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Lepcha,
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Limbu,
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Linear_A,
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Linear_B,
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Lisu,
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Lycian,
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Lydian,
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Mahajani,
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Malayalam,
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Mandaic,
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Manichaean,
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Meetei_Mayek,
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Mende_Kikakui,
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Meroitic_Cursive,
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Meroitic_Hieroglyphs,
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Miao,
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Modi,
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Mongolian,
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Mro,
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Multani,
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Myanmar,
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Nabataean,
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New_Tai_Lue,
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Nko,
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Ogham,
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Ol_Chiki,
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Old_Hungarian,
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Old_Italic,
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Old_North_Arabian,
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Old_Permic,
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Old_Persian,
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Old_South_Arabian,
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Old_Turkic,
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Oriya,
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Osmanya,
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Pahawh_Hmong,
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Palmyrene,
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Pau_Cin_Hau,
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Phags_Pa,
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Phoenician,
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Psalter_Pahlavi,
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Rejang,
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Runic,
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Samaritan,
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Saurashtra,
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Sharada,
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Shavian,
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Siddham,
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SignWriting,
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Sinhala,
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Sora_Sompeng,
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Sundanese,
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Syloti_Nagri,
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Syriac,
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Tagalog,
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Tagbanwa,
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Tai_Le,
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Tai_Tham,
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Tai_Viet,
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Takri,
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Tamil,
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Telugu,
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Thaana,
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Thai,
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Tibetan,
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Tifinagh,
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Tirhuta,
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Ugaritic,
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Vai,
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Warang_Citi,
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Yi.
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</P>
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<br><a name="SEC8" href="#TOC1">CHARACTER CLASSES</a><br>
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<P>
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<pre>
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[...] positive character class
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[^...] negative character class
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[x-y] range (can be used for hex characters)
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[[:xxx:]] positive POSIX named set
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[[:^xxx:]] negative POSIX named set
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alnum alphanumeric
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alpha alphabetic
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ascii 0-127
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blank space or tab
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cntrl control character
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digit decimal digit
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graph printing, excluding space
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lower lower case letter
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print printing, including space
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punct printing, excluding alphanumeric
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space white space
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upper upper case letter
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word same as \w
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xdigit hexadecimal digit
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</pre>
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In PCRE2, POSIX character set names recognize only ASCII characters by default,
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but some of them use Unicode properties if PCRE2_UCP is set. You can use
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\Q...\E inside a character class.
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</P>
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<br><a name="SEC9" href="#TOC1">QUANTIFIERS</a><br>
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<P>
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<pre>
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? 0 or 1, greedy
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?+ 0 or 1, possessive
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?? 0 or 1, lazy
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* 0 or more, greedy
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*+ 0 or more, possessive
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*? 0 or more, lazy
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+ 1 or more, greedy
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++ 1 or more, possessive
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+? 1 or more, lazy
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{n} exactly n
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{n,m} at least n, no more than m, greedy
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{n,m}+ at least n, no more than m, possessive
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{n,m}? at least n, no more than m, lazy
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{n,} n or more, greedy
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{n,}+ n or more, possessive
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{n,}? n or more, lazy
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</PRE>
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</P>
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<br><a name="SEC10" href="#TOC1">ANCHORS AND SIMPLE ASSERTIONS</a><br>
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<P>
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<pre>
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\b word boundary
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\B not a word boundary
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^ start of subject
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also after an internal newline in multiline mode
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(after any newline if PCRE2_ALT_CIRCUMFLEX is set)
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\A start of subject
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$ end of subject
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also before newline at end of subject
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also before internal newline in multiline mode
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\Z end of subject
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also before newline at end of subject
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\z end of subject
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\G first matching position in subject
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</PRE>
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</P>
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<br><a name="SEC11" href="#TOC1">MATCH POINT RESET</a><br>
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<P>
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<pre>
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\K reset start of match
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</pre>
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\K is honoured in positive assertions, but ignored in negative ones.
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</P>
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<br><a name="SEC12" href="#TOC1">ALTERNATION</a><br>
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<P>
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<pre>
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expr|expr|expr...
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</PRE>
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</P>
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<br><a name="SEC13" href="#TOC1">CAPTURING</a><br>
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<P>
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<pre>
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(...) capturing group
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(?<name>...) named capturing group (Perl)
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(?'name'...) named capturing group (Perl)
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(?P<name>...) named capturing group (Python)
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(?:...) non-capturing group
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(?|...) non-capturing group; reset group numbers for
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capturing groups in each alternative
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</PRE>
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</P>
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<br><a name="SEC14" href="#TOC1">ATOMIC GROUPS</a><br>
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<P>
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<pre>
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(?>...) atomic, non-capturing group
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</PRE>
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</P>
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<br><a name="SEC15" href="#TOC1">COMMENT</a><br>
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<P>
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<pre>
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(?#....) comment (not nestable)
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</PRE>
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</P>
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<br><a name="SEC16" href="#TOC1">OPTION SETTING</a><br>
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<P>
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<pre>
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(?i) caseless
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(?J) allow duplicate names
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(?m) multiline
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(?n) no auto capture
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(?s) single line (dotall)
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(?U) default ungreedy (lazy)
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(?x) extended: ignore white space except in classes
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(?xx) as (?x) but also ignore space and tab in classes
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(?-...) unset option(s)
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</pre>
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The following are recognized only at the very start of a pattern or after one
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of the newline or \R options with similar syntax. More than one of them may
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appear.
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<pre>
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(*LIMIT_MATCH=d) set the match limit to d (decimal number)
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(*LIMIT_DEPTH=d) set the backtracking limit to d (decimal number)
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(*NOTEMPTY) set PCRE2_NOTEMPTY when matching
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(*NOTEMPTY_ATSTART) set PCRE2_NOTEMPTY_ATSTART when matching
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(*NO_AUTO_POSSESS) no auto-possessification (PCRE2_NO_AUTO_POSSESS)
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(*NO_DOTSTAR_ANCHOR) no .* anchoring (PCRE2_NO_DOTSTAR_ANCHOR)
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(*NO_JIT) disable JIT optimization
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(*NO_START_OPT) no start-match optimization (PCRE2_NO_START_OPTIMIZE)
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(*UTF) set appropriate UTF mode for the library in use
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(*UCP) set PCRE2_UCP (use Unicode properties for \d etc)
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</pre>
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Note that LIMIT_MATCH and LIMIT_DEPTH can only reduce the value of the limits
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set by the caller of <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b>, not
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increase them. LIMIT_RECURSION is an obsolete synonym for LIMIT_DEPTH. The
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application can lock out the use of (*UTF) and (*UCP) by setting the
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PCRE2_NEVER_UTF or PCRE2_NEVER_UCP options, respectively, at compile time.
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</P>
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<br><a name="SEC17" href="#TOC1">NEWLINE CONVENTION</a><br>
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<P>
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These are recognized only at the very start of the pattern or after option
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settings with a similar syntax.
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<pre>
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(*CR) carriage return only
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(*LF) linefeed only
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(*CRLF) carriage return followed by linefeed
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(*ANYCRLF) all three of the above
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(*ANY) any Unicode newline sequence
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</PRE>
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</P>
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<br><a name="SEC18" href="#TOC1">WHAT \R MATCHES</a><br>
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<P>
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These are recognized only at the very start of the pattern or after option
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setting with a similar syntax.
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<pre>
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(*BSR_ANYCRLF) CR, LF, or CRLF
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(*BSR_UNICODE) any Unicode newline sequence
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</PRE>
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</P>
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<br><a name="SEC19" href="#TOC1">LOOKAHEAD AND LOOKBEHIND ASSERTIONS</a><br>
|
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<P>
|
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<pre>
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(?=...) positive look ahead
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(?!...) negative look ahead
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(?<=...) positive look behind
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(?<!...) negative look behind
|
|
</pre>
|
|
Each top-level branch of a look behind must be of a fixed length.
|
|
</P>
|
|
<br><a name="SEC20" 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="SEC21" href="#TOC1">SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)</a><br>
|
|
<P>
|
|
<pre>
|
|
(?R) recurse whole pattern
|
|
(?n) call subpattern by absolute number
|
|
(?+n) call subpattern by relative number
|
|
(?-n) call subpattern by relative number
|
|
(?&name) call subpattern by name (Perl)
|
|
(?P>name) call subpattern by name (Python)
|
|
\g<name> call subpattern by name (Oniguruma)
|
|
\g'name' call subpattern by name (Oniguruma)
|
|
\g<n> call subpattern by absolute number (Oniguruma)
|
|
\g'n' call subpattern by absolute number (Oniguruma)
|
|
\g<+n> call subpattern by relative number (PCRE2 extension)
|
|
\g'+n' call subpattern by relative number (PCRE2 extension)
|
|
\g<-n> call subpattern by relative number (PCRE2 extension)
|
|
\g'-n' call subpattern by relative number (PCRE2 extension)
|
|
</PRE>
|
|
</P>
|
|
<br><a name="SEC22" 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 subpattern 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="SEC23" href="#TOC1">BACKTRACKING CONTROL</a><br>
|
|
<P>
|
|
The following act immediately they are reached:
|
|
<pre>
|
|
(*ACCEPT) force successful match
|
|
(*FAIL) force backtrack; synonym (*F)
|
|
(*MARK:NAME) set name to be passed back; synonym (*:NAME)
|
|
</pre>
|
|
The following act only when a subsequent match failure causes a backtrack to
|
|
reach them. They all force a match failure, but they differ in what happens
|
|
afterwards. Those that advance the start-of-match point do so only if the
|
|
pattern is not anchored.
|
|
<pre>
|
|
(*COMMIT) overall failure, no advance of starting point
|
|
(*PRUNE) advance to next starting character
|
|
(*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE)
|
|
(*SKIP) advance to current matching position
|
|
(*SKIP:NAME) advance to position corresponding to an earlier
|
|
(*MARK:NAME); if not found, the (*SKIP) is ignored
|
|
(*THEN) local failure, backtrack to next alternation
|
|
(*THEN:NAME) equivalent to (*MARK:NAME)(*THEN)
|
|
</PRE>
|
|
</P>
|
|
<br><a name="SEC24" 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="SEC25" 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="SEC26" href="#TOC1">AUTHOR</a><br>
|
|
<P>
|
|
Philip Hazel
|
|
<br>
|
|
University Computing Service
|
|
<br>
|
|
Cambridge, England.
|
|
<br>
|
|
</P>
|
|
<br><a name="SEC27" href="#TOC1">REVISION</a><br>
|
|
<P>
|
|
Last updated: 18 April 2017
|
|
<br>
|
|
Copyright © 1997-2017 University of Cambridge.
|
|
<br>
|
|
<p>
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
</p>
|