.TH PCRESYNTAX 3 "11 November 2012" "PCRE 8.32"

 .SH NAME

 PCRE - Perl-compatible regular expressions

 .SH "PCRE REGULAR EXPRESSION SYNTAX SUMMARY"

 .rs

 .sp

 The full syntax and semantics of the regular expressions that are supported by

 PCRE are described in the

 .\" HREF

 \fBpcrepattern\fP

 .\"

 documentation. This document contains a quick-reference summary of the syntax.

 .

 .

 .SH "QUOTING"

 .rs

 .sp

   \ex         where x is non-alphanumeric is a literal x

   \eQ...\eE    treat enclosed characters as literal

 .

 .

 .SH "CHARACTERS"

 .rs

 .sp

   \ea         alarm, that is, the BEL character (hex 07)

   \ecx        "control-x", where x is any ASCII character

   \ee         escape (hex 1B)

   \ef         form feed (hex 0C)

   \en         newline (hex 0A)

   \er         carriage return (hex 0D)

   \et         tab (hex 09)

   \eddd       character with octal code ddd, or backreference

   \exhh       character with hex code hh

   \ex{hhh..}  character with hex code hhh..

 .

 .

 .SH "CHARACTER TYPES"

 .rs

 .sp

   .          any character except newline;

                in dotall mode, any character whatsoever

   \eC         one data unit, even in UTF mode (best avoided)

   \ed         a decimal digit

   \eD         a character that is not a decimal digit

   \eh         a horizontal white space character

   \eH         a character that is not a horizontal white space character

   \eN         a character that is not a newline

   \ep{\fIxx\fP}     a character with the \fIxx\fP property

   \eP{\fIxx\fP}     a character without the \fIxx\fP property

   \eR         a newline sequence

   \es         a white space character

   \eS         a character that is not a white space character

   \ev         a vertical white space character

   \eV         a character that is not a vertical white space character

   \ew         a "word" character

   \eW         a "non-word" character

   \eX         a Unicode extended grapheme cluster

 .sp

 In PCRE, by default, \ed, \eD, \es, \eS, \ew, and \eW recognize only ASCII

 characters, even in a UTF mode. However, this can be changed by setting the

 PCRE_UCP option.

 .

 .

 .SH "GENERAL CATEGORY PROPERTIES FOR \ep and \eP"

 .rs

 .sp

   C          Other

   Cc         Control

   Cf         Format

   Cn         Unassigned

   Co         Private use

   Cs         Surrogate

 .sp

   L          Letter

   Ll         Lower case letter

   Lm         Modifier letter

   Lo         Other letter

   Lt         Title case letter

   Lu         Upper case letter

   L&         Ll, Lu, or Lt

 .sp

   M          Mark

   Mc         Spacing mark

   Me         Enclosing mark

   Mn         Non-spacing mark

 .sp

   N          Number

   Nd         Decimal number

   Nl         Letter number

   No         Other number

 .sp

   P          Punctuation

   Pc         Connector punctuation

   Pd         Dash punctuation

   Pe         Close punctuation

   Pf         Final punctuation

   Pi         Initial punctuation

   Po         Other punctuation

   Ps         Open punctuation

 .sp

   S          Symbol

   Sc         Currency symbol

   Sk         Modifier symbol

   Sm         Mathematical symbol

   So         Other symbol

 .sp

   Z          Separator

   Zl         Line separator

   Zp         Paragraph separator

   Zs         Space separator

 .

 .

 .SH "PCRE SPECIAL CATEGORY PROPERTIES FOR \ep and \eP"

 .rs

 .sp

   Xan        Alphanumeric: union of properties L and N

   Xps        POSIX space: property Z or tab, NL, VT, FF, CR

   Xsp        Perl space: property Z or tab, NL, FF, CR

   Xwd        Perl word: property Xan or underscore

 .

 .

 .SH "SCRIPT NAMES FOR \ep AND \eP"

 .rs

 .sp

 Arabic,

 Armenian,

 Avestan,

 Balinese,

 Bamum,

 Batak,

 Bengali,

 Bopomofo,

 Brahmi,

 Braille,

 Buginese,

 Buhid,

 Canadian_Aboriginal,

 Carian,

 Chakma,

 Cham,

 Cherokee,

 Common,

 Coptic,

 Cuneiform,

 Cypriot,

 Cyrillic,

 Deseret,

 Devanagari,

 Egyptian_Hieroglyphs,

 Ethiopic,

 Georgian,

 Glagolitic,

 Gothic,

 Greek,

 Gujarati,

 Gurmukhi,

 Han,

 Hangul,

 Hanunoo,

 Hebrew,

 Hiragana,

 Imperial_Aramaic,

 Inherited,

 Inscriptional_Pahlavi,

 Inscriptional_Parthian,

 Javanese,

 Kaithi,

 Kannada,

 Katakana,

 Kayah_Li,

 Kharoshthi,

 Khmer,

 Lao,

 Latin,

 Lepcha,

 Limbu,

 Linear_B,

 Lisu,

 Lycian,

 Lydian,

 Malayalam,

 Mandaic,

 Meetei_Mayek,

 Meroitic_Cursive,

 Meroitic_Hieroglyphs,

 Miao,

 Mongolian,

 Myanmar,

 New_Tai_Lue,

 Nko,

 Ogham,

 Old_Italic,

 Old_Persian,

 Old_South_Arabian,

 Old_Turkic,

 Ol_Chiki,

 Oriya,

 Osmanya,

 Phags_Pa,

 Phoenician,

 Rejang,

 Runic,

 Samaritan,

 Saurashtra,

 Sharada,

 Shavian,

 Sinhala,

 Sora_Sompeng,

 Sundanese,

 Syloti_Nagri,

 Syriac,

 Tagalog,

 Tagbanwa,

 Tai_Le,

 Tai_Tham,

 Tai_Viet,

 Takri,

 Tamil,

 Telugu,

 Thaana,

 Thai,

 Tibetan,

 Tifinagh,

 Ugaritic,

 Vai,

 Yi.

 .

 .

 .SH "CHARACTER CLASSES"

 .rs

 .sp

   [...]       positive character class

   [^...]      negative character class

   [x-y]       range (can be used for hex characters)

   [[:xxx:]]   positive POSIX named set

   [[:^xxx:]]  negative POSIX named set

 .sp

   alnum       alphanumeric

   alpha       alphabetic

   ascii       0-127

   blank       space or tab

   cntrl       control character

   digit       decimal digit

   graph       printing, excluding space

   lower       lower case letter

   print       printing, including space

   punct       printing, excluding alphanumeric

   space       white space

   upper       upper case letter

   word        same as \ew

   xdigit      hexadecimal digit

 .sp

 In PCRE, POSIX character set names recognize only ASCII characters by default,

 but some of them use Unicode properties if PCRE_UCP is set. You can use

 \eQ...\eE inside a character class.

 .

 .

 .SH "QUANTIFIERS"

 .rs

 .sp

   ?           0 or 1, greedy

   ?+          0 or 1, possessive

   ??          0 or 1, lazy

   *           0 or more, greedy

   *+          0 or more, possessive

   *?          0 or more, lazy

   +           1 or more, greedy

   ++          1 or more, possessive

   +?          1 or more, lazy

   {n}         exactly n

   {n,m}       at least n, no more than m, greedy

   {n,m}+      at least n, no more than m, possessive

   {n,m}?      at least n, no more than m, lazy

   {n,}        n or more, greedy

   {n,}+       n or more, possessive

   {n,}?       n or more, lazy

 .

 .

 .SH "ANCHORS AND SIMPLE ASSERTIONS"

 .rs

 .sp

   \eb          word boundary

   \eB          not a word boundary

   ^           start of subject

                also after internal newline in multiline mode

   \eA          start of subject

   $           end of subject

                also before newline at end of subject

                also before internal newline in multiline mode

   \eZ          end of subject

                also before newline at end of subject

   \ez          end of subject

   \eG          first matching position in subject

 .

 .

 .SH "MATCH POINT RESET"

 .rs

 .sp

   \eK          reset start of match

 .

 .

 .SH "ALTERNATION"

 .rs

 .sp

   expr|expr|expr...

 .

 .

 .SH "CAPTURING"

 .rs

 .sp

   (...)           capturing group

   (?<name>...)    named capturing group (Perl)

   (?'name'...)    named capturing group (Perl)

   (?P<name>...)   named capturing group (Python)

   (?:...)         non-capturing group

   (?|...)         non-capturing group; reset group numbers for

                    capturing groups in each alternative

 .

 .

 .SH "ATOMIC GROUPS"

 .rs

 .sp

   (?>...)         atomic, non-capturing group

 .

 .

 .

 .

 .SH "COMMENT"

 .rs

 .sp

   (?#....)        comment (not nestable)

 .

 .

 .SH "OPTION SETTING"

 .rs

 .sp

   (?i)            caseless

   (?J)            allow duplicate names

   (?m)            multiline

   (?s)            single line (dotall)

   (?U)            default ungreedy (lazy)

   (?x)            extended (ignore white space)

   (?-...)         unset option(s)

 .sp

 The following are recognized only at the start of a pattern or after one of the

 newline-setting options with similar syntax:

 .sp

   (*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)

   (*UTF8)         set UTF-8 mode: 8-bit library (PCRE_UTF8)

   (*UTF16)        set UTF-16 mode: 16-bit library (PCRE_UTF16)

   (*UTF32)        set UTF-32 mode: 32-bit library (PCRE_UTF32)

   (*UTF)          set appropriate UTF mode for the library in use

   (*UCP)          set PCRE_UCP (use Unicode properties for \ed etc)

 .

 .

 .SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS"

 .rs

 .sp

   (?=...)         positive look ahead

   (?!...)         negative look ahead

   (?<=...)        positive look behind

   (?<!...)        negative look behind

 .sp

 Each top-level branch of a look behind must be of a fixed length.

 .

 .

 .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

   \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 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)

   \eg<name>        call subpattern by name (Oniguruma)

   \eg'name'        call subpattern by name (Oniguruma)

   \eg<n>           call subpattern by absolute number (Oniguruma)

   \eg'n'           call subpattern by absolute number (Oniguruma)

   \eg<+n>          call subpattern by relative number (PCRE extension)

   \eg'+n'          call subpattern by relative number (PCRE extension)

   \eg<-n>          call subpattern by relative number (PCRE extension)

   \eg'-n'          call subpattern by relative number (PCRE 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 (PCRE)

   (?(R)...        overall recursion condition

   (?(Rn)...       specific group recursion condition

   (?(R&name)...   specific recursion condition

   (?(DEFINE)...   define subpattern for reference

   (?(assert)...   assertion condition

 .

 .

 .SH "BACKTRACKING CONTROL"

 .rs

 .sp

 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

   (*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)

 .

 .

 .SH "NEWLINE CONVENTIONS"

 .rs

 .sp

 These are recognized only at the very start of the pattern or after a

 (*BSR_...), (*UTF8), (*UTF16), (*UTF32) or (*UCP) option.

 .sp

   (*CR)           carriage return only

   (*LF)           linefeed only

   (*CRLF)         carriage return followed by linefeed

   (*ANYCRLF)      all three of the above

   (*ANY)          any Unicode newline sequence

 .

 .

 .SH "WHAT \eR MATCHES"

 .rs

 .sp

 These are recognized only at the very start of the pattern or after a

 (*...) option that sets the newline convention or a UTF or UCP mode.

 .sp

   (*BSR_ANYCRLF)  CR, LF, or CRLF

   (*BSR_UNICODE)  any Unicode newline sequence

 .

 .

 .SH "CALLOUTS"

 .rs

 .sp

   (?C)      callout

   (?Cn)     callout with data n

 .

 .

 .SH "SEE ALSO"

 .rs

 .sp

 \fBpcrepattern\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3),

 \fBpcrematching\fP(3), \fBpcre\fP(3).

 .

 .

 .SH AUTHOR

 .rs

 .sp

 .nf

 Philip Hazel

 University Computing Service

 Cambridge CB2 3QH, England.

 .fi

 .

 .

 .SH REVISION

 .rs

 .sp

 .nf

 Last updated: 11 November 2012

 Copyright (c) 1997-2012 University of Cambridge.

 .fi