685 lines
19 KiB
Groff
685 lines
19 KiB
Groff
.TH PCRE2SYNTAX 3 "30 August 2021" "PCRE2 10.38"
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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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This table applies to ASCII and Unicode environments. An unrecognized escape
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sequence causes an error.
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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 printing 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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\eN{U+hh..} character with Unicode code point hh.. (Unicode mode only)
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\exhh character with hex code hh
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\ex{hh..} character with hex code hh..
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.sp
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If PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX is set ("ALT_BSUX mode"), the
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following are also recognized:
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.sp
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\eU the character "U"
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\euhhhh character with hex code hhhh
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\eu{hh..} character with hex code hh.. but only for EXTRA_ALT_BSUX
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.sp
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When \ex is not followed by {, from zero to two hexadecimal digits are read,
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but in ALT_BSUX mode \ex must be followed by two hexadecimal digits to be
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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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or (in EXTRA_ALT_BSUX mode) a sequence of hex digits in curly brackets, it
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matches a literal "u".
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.P
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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, where details of escape processing in EBCDIC environments are
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also given. \eN{U+hh..} is synonymous with \ex{hh..} in PCRE2 but is not
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supported in EBCDIC environments. Note that \eN not followed by an opening
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curly bracket has a different meaning (see below).
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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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\eC 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 \eC 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 \eC permanently disabled.
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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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Adlam,
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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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Bhaiksuki,
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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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Chorasmian,
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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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Dives_Akuru,
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Dogra,
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Duployan,
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Egyptian_Hieroglyphs,
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Elbasan,
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Elymaic,
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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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Gunjala_Gondi,
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Gurmukhi,
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Han,
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Hangul,
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Hanifi_Rohingya,
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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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Khitan_Small_Script,
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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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Makasar,
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Malayalam,
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Mandaic,
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Manichaean,
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Marchen,
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Masaram_Gondi,
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Medefaidrin,
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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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Nandinagari,
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New_Tai_Lue,
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Newa,
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Nko,
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Nushu,
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Nyakeng_Puachue_Hmong,
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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_Sogdian,
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Old_South_Arabian,
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Old_Turkic,
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Oriya,
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Osage,
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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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Sogdian,
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Sora_Sompeng,
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Soyombo,
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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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Tangut,
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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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Wancho,
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Warang_Citi,
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Yezidi,
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Yi,
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Zanabazar_Square.
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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 "REPORTED MATCH POINT SETTING"
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.rs
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.sp
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\eK set reported start of match
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.sp
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From release 10.38 \eK is not permitted by default in lookaround assertions,
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for compatibility with Perl. However, if the PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK
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option is set, the previous behaviour is re-enabled. When this option is set,
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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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(...) capture group
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(?<name>...) named capture group (Perl)
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(?'name'...) named capture group (Perl)
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(?P<name>...) named capture group (Python)
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(?:...) non-capture group
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(?|...) non-capture group; reset group numbers for
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capture groups in each alternative
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.sp
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In non-UTF modes, names may contain underscores and ASCII letters and digits;
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in UTF modes, any Unicode letters and Unicode decimal digits are permitted. In
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both cases, a name must not start with a digit.
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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-capture group
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(*atomic:...) atomic non-capture group
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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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Changes of these options within a group are automatically cancelled at the end
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of the group.
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.sp
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(?i) caseless
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(?J) allow duplicate named groups
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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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(?^) unset imnsx options
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.sp
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Unsetting x or xx unsets both. Several options may be set at once, and a
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mixture of setting and unsetting such as (?i-x) is allowed, but there may be
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only one hyphen. Setting (but no unsetting) is allowed after (?^ for example
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(?^in). An option setting may appear at the start of a non-capture group, for
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example (?i:...).
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.P
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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. For the first three, d is a decimal number.
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.sp
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(*LIMIT_DEPTH=d) set the backtracking limit to d
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(*LIMIT_HEAP=d) set the heap size limit to d * 1024 bytes
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(*LIMIT_MATCH=d) set the match limit to d
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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_DEPTH, LIMIT_HEAP, and LIMIT_MATCH can only reduce the value of
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the limits set by the caller of \fBpcre2_match()\fP or \fBpcre2_dfa_match()\fP,
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not 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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.
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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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(*NUL) the NUL character (binary zero)
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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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(?=...) )
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(*pla:...) ) positive lookahead
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(*positive_lookahead:...) )
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.sp
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(?!...) )
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(*nla:...) ) negative lookahead
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(*negative_lookahead:...) )
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.sp
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(?<=...) )
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(*plb:...) ) positive lookbehind
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(*positive_lookbehind:...) )
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.sp
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(?<!...) )
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(*nlb:...) ) negative lookbehind
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(*negative_lookbehind:...) )
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.sp
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Each top-level branch of a lookbehind must be of a fixed length.
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.
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.
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.SH "NON-ATOMIC LOOKAROUND ASSERTIONS"
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.rs
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.sp
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These assertions are specific to PCRE2 and are not Perl-compatible.
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.sp
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(?*...) )
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(*napla:...) ) synonyms
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|
(*non_atomic_positive_lookahead:...) )
|
|
.sp
|
|
(?<*...) )
|
|
(*naplb:...) ) synonyms
|
|
(*non_atomic_positive_lookbehind:...) )
|
|
.
|
|
.
|
|
.SH "SCRIPT RUNS"
|
|
.rs
|
|
.sp
|
|
(*script_run:...) ) script run, can be backtracked into
|
|
(*sr:...) )
|
|
.sp
|
|
(*atomic_script_run:...) ) atomic script run
|
|
(*asr:...) )
|
|
.
|
|
.
|
|
.SH "BACKREFERENCES"
|
|
.rs
|
|
.sp
|
|
\en reference by number (can be ambiguous)
|
|
\egn reference by number
|
|
\eg{n} reference by number
|
|
\eg+n relative reference by number (PCRE2 extension)
|
|
\eg-n relative reference by number
|
|
\eg{+n} relative reference by number (PCRE2 extension)
|
|
\eg{-n} relative reference by number
|
|
\ek<name> reference by name (Perl)
|
|
\ek'name' reference by name (Perl)
|
|
\eg{name} reference by name (Perl)
|
|
\ek{name} reference by name (.NET)
|
|
(?P=name) reference by name (Python)
|
|
.
|
|
.
|
|
.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)"
|
|
.rs
|
|
.sp
|
|
(?R) recurse whole pattern
|
|
(?n) call 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)
|
|
\eg<name> call subroutine by name (Oniguruma)
|
|
\eg'name' call subroutine by name (Oniguruma)
|
|
\eg<n> call subroutine by absolute number (Oniguruma)
|
|
\eg'n' call subroutine by absolute number (Oniguruma)
|
|
\eg<+n> call subroutine by relative number (PCRE2 extension)
|
|
\eg'+n' call subroutine by relative number (PCRE2 extension)
|
|
\eg<-n> call subroutine by relative number (PCRE2 extension)
|
|
\eg'-n' call subroutine by relative number (PCRE2 extension)
|
|
.
|
|
.
|
|
.SH "CONDITIONAL PATTERNS"
|
|
.rs
|
|
.sp
|
|
(?(condition)yes-pattern)
|
|
(?(condition)yes-pattern|no-pattern)
|
|
.sp
|
|
(?(n) absolute reference condition
|
|
(?(+n) relative reference condition
|
|
(?(-n) relative reference condition
|
|
(?(<name>) named reference condition (Perl)
|
|
(?('name') named reference condition (Perl)
|
|
(?(name) named reference condition (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
|
|
.sp
|
|
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.
|
|
.
|
|
.
|
|
.SH "BACKTRACKING CONTROL"
|
|
.rs
|
|
.sp
|
|
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:
|
|
.sp
|
|
(*ACCEPT) force successful match
|
|
(*FAIL) force backtrack; synonym (*F)
|
|
(*MARK:NAME) set name to be passed back; synonym (*:NAME)
|
|
.sp
|
|
The following act only when a subsequent match failure causes a backtrack to
|
|
reach them. They all force a match failure, but they differ in what happens
|
|
afterwards. Those that advance the start-of-match point do so only if the
|
|
pattern is not anchored.
|
|
.sp
|
|
(*COMMIT) overall failure, no advance of starting point
|
|
(*PRUNE) advance to next starting character
|
|
(*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
|
|
.sp
|
|
The effect of one of these verbs in a group called as a subroutine is confined
|
|
to the subroutine call.
|
|
.
|
|
.
|
|
.SH "CALLOUTS"
|
|
.rs
|
|
.sp
|
|
(?C) callout (assumed number 0)
|
|
(?Cn) callout with numerical data n
|
|
(?C"text") callout with string data
|
|
.sp
|
|
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.
|
|
.
|
|
.
|
|
.SH "SEE ALSO"
|
|
.rs
|
|
.sp
|
|
\fBpcre2pattern\fP(3), \fBpcre2api\fP(3), \fBpcre2callout\fP(3),
|
|
\fBpcre2matching\fP(3), \fBpcre2\fP(3).
|
|
.
|
|
.
|
|
.SH AUTHOR
|
|
.rs
|
|
.sp
|
|
.nf
|
|
Philip Hazel
|
|
Retired from University Computing Service
|
|
Cambridge, England.
|
|
.fi
|
|
.
|
|
.
|
|
.SH REVISION
|
|
.rs
|
|
.sp
|
|
.nf
|
|
Last updated: 30 August 2021
|
|
Copyright (c) 1997-2021 University of Cambridge.
|
|
.fi
|