573 lines
15 KiB
Groff
573 lines
15 KiB
Groff
.TH PCRE2SYNTAX 3 "23 April 2015" "PCRE2 10.20"
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.SH NAME
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PCRE2 - Perl-compatible regular expressions (revised API)
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.SH "PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY"
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.rs
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.sp
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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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.\" HREF
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\fBpcre2pattern\fP
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.\"
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documentation. This document contains a quick-reference summary of the syntax.
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.
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.
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.SH "QUOTING"
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.rs
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.sp
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\ex where x is non-alphanumeric is a literal x
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\eQ...\eE treat enclosed characters as literal
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.
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.
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.SH "ESCAPED CHARACTERS"
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.rs
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.sp
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\ea alarm, that is, the BEL character (hex 07)
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\ecx "control-x", where x is any ASCII character
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\ee escape (hex 1B)
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\ef form feed (hex 0C)
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\en newline (hex 0A)
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\er carriage return (hex 0D)
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\et tab (hex 09)
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\e0dd character with octal code 0dd
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\eddd character with octal code ddd, or backreference
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\eo{ddd..} character with octal code ddd..
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\eU "U" if PCRE2_ALT_BSUX is set (otherwise is an error)
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\euhhhh character with hex code hhhh (if PCRE2_ALT_BSUX is set)
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\exhh character with hex code hh
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\ex{hhh..} character with hex code hhh..
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.sp
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Note that \e0dd 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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.\" HTML <a href="pcre2pattern.html#digitsafterbackslash">
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.\" </a>
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"Non-printing characters"
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.\"
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in the
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.\" HREF
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\fBpcre2pattern\fP
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.\"
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documentation.
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.P
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When \ex is not followed by {, from zero to two hexadecimal digits are read,
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but if PCRE2_ALT_BSUX is set, \ex 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 \eu (in ALT_BSUX mode) is not followed by four hexadecimal digits,
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it matches a literal "u".
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.
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.
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.SH "CHARACTER TYPES"
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.rs
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.sp
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. any character except newline;
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in dotall mode, any character whatsoever
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\eC one code unit, even in UTF mode (best avoided)
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\ed a decimal digit
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\eD a character that is not a decimal digit
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\eh a horizontal white space character
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\eH a character that is not a horizontal white space character
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\eN a character that is not a newline
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\ep{\fIxx\fP} a character with the \fIxx\fP property
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\eP{\fIxx\fP} a character without the \fIxx\fP property
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\eR a newline sequence
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\es a white space character
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\eS a character that is not a white space character
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\ev a vertical white space character
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\eV a character that is not a vertical white space character
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\ew a "word" character
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\eW a "non-word" character
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\eX a Unicode extended grapheme cluster
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.sp
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The application can lock out the use of \eC by setting the
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PCRE2_NEVER_BACKSLASH_C option. It is dangerous because it may leave the
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current matching point in the middle of a UTF-8 or UTF-16 character.
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.P
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By default, \ed, \es, and \ew 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, \es and \ew 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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.
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.
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.SH "GENERAL CATEGORY PROPERTIES FOR \ep and \eP"
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.rs
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.sp
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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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.sp
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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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.sp
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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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.sp
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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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.sp
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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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.sp
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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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.sp
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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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.
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.
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.SH "PCRE2 SPECIAL CATEGORY PROPERTIES FOR \ep and \eP"
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.rs
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.sp
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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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.sp
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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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.
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.
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.SH "SCRIPT NAMES FOR \ep AND \eP"
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.rs
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.sp
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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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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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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_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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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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.
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.
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.SH "CHARACTER CLASSES"
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.rs
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.sp
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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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.sp
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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 \ew
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xdigit hexadecimal digit
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.sp
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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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\eQ...\eE inside a character class.
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.
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.
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.SH "QUANTIFIERS"
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.rs
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.sp
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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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.
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.
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.SH "ANCHORS AND SIMPLE ASSERTIONS"
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.rs
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.sp
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\eb word boundary
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\eB 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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\eA 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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\eZ end of subject
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also before newline at end of subject
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\ez end of subject
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\eG first matching position in subject
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.
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.
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.SH "MATCH POINT RESET"
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.rs
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.sp
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\eK reset start of match
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.sp
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\eK is honoured in positive assertions, but ignored in negative ones.
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.
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.
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.SH "ALTERNATION"
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.rs
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.sp
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expr|expr|expr...
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.
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.
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.SH "CAPTURING"
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.rs
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.sp
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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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.
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.
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.SH "ATOMIC GROUPS"
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.rs
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.sp
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(?>...) atomic, non-capturing group
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.
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.
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.
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.
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.SH "COMMENT"
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.rs
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.sp
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(?#....) comment (not nestable)
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.
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.
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.SH "OPTION SETTING"
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.rs
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.sp
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(?i) caseless
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(?J) allow duplicate names
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(?m) multiline
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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)
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(?-...) unset option(s)
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.sp
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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 \eR options with similar syntax. More than one of them may
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appear.
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.sp
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(*LIMIT_MATCH=d) set the match limit to d (decimal number)
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(*LIMIT_RECURSION=d) set the recursion 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 \ed etc)
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.sp
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Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the
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limits set by the caller of pcre2_match(), not increase them. The application
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can lock out the use of (*UTF) and (*UCP) by setting the PCRE2_NEVER_UTF or
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PCRE2_NEVER_UCP options, respectively, at compile time.
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.
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.
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.SH "NEWLINE CONVENTION"
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.rs
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.sp
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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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.sp
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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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.
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.
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.SH "WHAT \eR MATCHES"
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.rs
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.sp
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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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.sp
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(*BSR_ANYCRLF) CR, LF, or CRLF
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(*BSR_UNICODE) any Unicode newline sequence
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.
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.
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.SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS"
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.rs
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.sp
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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
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.sp
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Each top-level branch of a look behind must be of a fixed length.
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.
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.
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.SH "BACKREFERENCES"
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.rs
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.sp
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\en reference by number (can be ambiguous)
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\egn reference by number
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\eg{n} reference by number
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\eg{-n} relative reference by number
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\ek<name> reference by name (Perl)
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\ek'name' reference by name (Perl)
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\eg{name} reference by name (Perl)
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\ek{name} reference by name (.NET)
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(?P=name) reference by name (Python)
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.
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.
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.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)"
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.rs
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.sp
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(?R) recurse whole pattern
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(?n) call subpattern by absolute number
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(?+n) call subpattern by relative number
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(?-n) call subpattern by relative number
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(?&name) call subpattern by name (Perl)
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(?P>name) call subpattern by name (Python)
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\eg<name> call subpattern by name (Oniguruma)
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\eg'name' call subpattern by name (Oniguruma)
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\eg<n> call subpattern by absolute number (Oniguruma)
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\eg'n' call subpattern by absolute number (Oniguruma)
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\eg<+n> call subpattern by relative number (PCRE2 extension)
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\eg'+n' call subpattern by relative number (PCRE2 extension)
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\eg<-n> call subpattern by relative number (PCRE2 extension)
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\eg'-n' call subpattern by relative number (PCRE2 extension)
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.
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.
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.SH "CONDITIONAL PATTERNS"
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.rs
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.sp
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(?(condition)yes-pattern)
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(?(condition)yes-pattern|no-pattern)
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.sp
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(?(n) absolute reference condition
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(?(+n) relative reference condition
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(?(-n) relative reference condition
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(?(<name>) named reference condition (Perl)
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(?('name') named reference condition (Perl)
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(?(name) named reference condition (PCRE2)
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(?(R) overall recursion condition
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(?(Rn) specific group recursion condition
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(?(R&name) specific recursion condition
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(?(DEFINE) define subpattern for reference
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(?(VERSION[>]=n.m) test PCRE2 version
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(?(assert) assertion condition
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.
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.
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.SH "BACKTRACKING CONTROL"
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.rs
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.sp
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The following act immediately they are reached:
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.sp
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(*ACCEPT) force successful match
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(*FAIL) force backtrack; synonym (*F)
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(*MARK:NAME) set name to be passed back; synonym (*:NAME)
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.sp
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The following act only when a subsequent match failure causes a backtrack to
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reach them. They all force a match failure, but they differ in what happens
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afterwards. Those that advance the start-of-match point do so only if the
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pattern is not anchored.
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.sp
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(*COMMIT) overall failure, no advance of starting point
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(*PRUNE) advance to next starting character
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(*PRUNE:NAME) equivalent to (*MARK:NAME)(*PRUNE)
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(*SKIP) advance to current matching position
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(*SKIP:NAME) advance to position corresponding to an earlier
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(*MARK:NAME); if not found, the (*SKIP) is ignored
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(*THEN) local failure, backtrack to next alternation
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(*THEN:NAME) equivalent to (*MARK:NAME)(*THEN)
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.
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.
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.SH "CALLOUTS"
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.rs
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.sp
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(?C) callout (assumed number 0)
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(?Cn) callout with numerical data n
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(?C"text") callout with string data
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.sp
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The allowed string delimiters are ` ' " ^ % # $ (which are the same for the
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start and the end), and the starting delimiter { matched with the ending
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delimiter }. To encode the ending delimiter within the string, double it.
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.
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.
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|
.SH "SEE ALSO"
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|
.rs
|
|
.sp
|
|
\fBpcre2pattern\fP(3), \fBpcre2api\fP(3), \fBpcre2callout\fP(3),
|
|
\fBpcre2matching\fP(3), \fBpcre2\fP(3).
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.
|
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.
|
|
.SH AUTHOR
|
|
.rs
|
|
.sp
|
|
.nf
|
|
Philip Hazel
|
|
University Computing Service
|
|
Cambridge, England.
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.fi
|
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.
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.
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.SH REVISION
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.rs
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|
.sp
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|
.nf
|
|
Last updated: 23 April 2015
|
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Copyright (c) 1997-2015 University of Cambridge.
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.fi
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