.TH PCRESYNTAX 3

.SH NAME

PCRE - Perl-compatible regular expressions

.SH "PCRE REGULAR EXPRESSION SYNTAX SUMMARY"

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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 just a quick-reference summary of the

syntax.

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.SH "QUOTING"

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

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

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.SH "CHARACTERS"

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

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

  \ee         escape (hex 1B)

  \ef         formfeed (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..

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.SH "CHARACTER TYPES"

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  .          any character except newline;

               in dotall mode, any character whatsoever

  \eC         one byte, even in UTF-8 mode (best avoided)

  \ed         a decimal digit

  \eD         a character that is not a decimal digit

  \eh         a horizontal whitespace character

  \eH         a character that is not a horizontal whitespace character

  \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 whitespace character

  \eS         a character that is not a whitespace character

  \ev         a vertical whitespace character

  \eV         a character that is not a vertical whitespace character

  \ew         a "word" character

  \eW         a "non-word" character

  \eX         an extended Unicode sequence

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In PCRE, \ed, \eD, \es, \eS, \ew, and \eW recognize only ASCII characters.

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.SH "GENERAL CATEGORY PROPERTY CODES FOR \ep and \eP"

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  C          Other

  Cc         Control

  Cf         Format

  Cn         Unassigned

  Co         Private use

  Cs         Surrogate

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  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

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  M          Mark

  Mc         Spacing mark

  Me         Enclosing mark

  Mn         Non-spacing mark

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  N          Number

  Nd         Decimal number

  Nl         Letter number

  No         Other number

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  P          Punctuation

  Pc         Connector punctuation

  Pd         Dash punctuation

  Pe         Close punctuation

  Pf         Final punctuation

  Pi         Initial punctuation

  Po         Other punctuation

  Ps         Open punctuation

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  S          Symbol

  Sc         Currency symbol

  Sk         Modifier symbol

  Sm         Mathematical symbol

  So         Other symbol

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  Z          Separator

  Zl         Line separator

  Zp         Paragraph separator

  Zs         Space separator

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

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Arabic,

Armenian,

Balinese,

Bengali,

Bopomofo,

Braille,

Buginese,

Buhid,

Canadian_Aboriginal,

Cherokee,

Common,

Coptic,

Cuneiform,

Cypriot,

Cyrillic,

Deseret,

Devanagari,

Ethiopic,

Georgian,

Glagolitic,

Gothic,

Greek,

Gujarati,

Gurmukhi,

Han,

Hangul,

Hanunoo,

Hebrew,

Hiragana,

Inherited,

Kannada,

Katakana,

Kharoshthi,

Khmer,

Lao,

Latin,

Limbu,

Linear_B,

Malayalam,

Mongolian,

Myanmar,

New_Tai_Lue,

Nko,

Ogham,

Old_Italic,

Old_Persian,

Oriya,

Osmanya,

Phags_Pa,

Phoenician,

Runic,

Shavian,

Sinhala,

Syloti_Nagri,

Syriac,

Tagalog,

Tagbanwa,

Tai_Le,

Tamil,

Telugu,

Thaana,

Thai,

Tibetan,

Tifinagh,

Ugaritic,

Yi.

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.SH "CHARACTER CLASSES"

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  [...]       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

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  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       whitespace

  upper       upper case letter

  word        same as \ew

  xdigit      hexadecimal digit

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In PCRE, POSIX character set names recognize only ASCII characters. You can use

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

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.SH "QUANTIFIERS"

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  ?           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

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.SH "ANCHORS AND SIMPLE ASSERTIONS"

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  \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

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.SH "MATCH POINT RESET"

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  \eK          reset start of match

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.SH "ALTERNATION"

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  expr|expr|expr...

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.SH "CAPTURING"

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  (...)          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

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.SH "ATOMIC GROUPS"

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

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.SH "COMMENT"

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

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.SH "OPTION SETTING"

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  (?i)           caseless

  (?J)           allow duplicate names

  (?m)           multiline

  (?s)           single line (dotall)

  (?U)           default ungreedy (lazy)

  (?x)           extended (ignore white space)

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

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.SH "LOOKAHEAD AND LOOKBEHIND ASSERTIONS"

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  (?=...)        positive look ahead

  (?!...)        negative look ahead

  (?<=...)       positive look behind

  (?<!...)       negative look behind

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

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.SH "BACKREFERENCES"

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  \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)

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.SH "SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)"

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  (?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)

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.SH "CONDITIONAL PATTERNS"

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  (?(condition)yes-pattern)

  (?(condition)yes-pattern|no-pattern)

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  (?(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

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.SH "BACKTRACKING CONTROL"

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The following act immediately they are reached:

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  (*ACCEPT)      force successful match

  (*FAIL)        force backtrack; synonym (*F)

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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.

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  (*COMMIT)      overall failure, no advance of starting point

  (*PRUNE)       advance to next starting character

  (*SKIP)        advance start to current matching position

  (*THEN)        local failure, backtrack to next alternation

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.SH "NEWLINE CONVENTIONS"

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

(*BSR_...) option.

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  (*CR)

  (*LF)

  (*CRLF)

  (*ANYCRLF)

  (*ANY)

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.SH "WHAT \eR MATCHES"

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

(*...) option that sets the newline convention.

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  (*BSR_ANYCRLF)

  (*BSR_UNICODE)

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.SH "CALLOUTS"

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  (?C)      callout

  (?Cn)     callout with data n

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.SH "SEE ALSO"

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

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

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.SH AUTHOR

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Philip Hazel

University Computing Service

Cambridge CB2 3QH, England.

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.SH REVISION

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Last updated: 09 April 2008

Copyright (c) 1997-2008 University of Cambridge.

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