NAME
PCRE2 - Perl-compatible regular expressions (revised API)PCRE2 REGULAR EXPRESSION SYNTAX SUMMARY
The full syntax and semantics of the regular expressions that are supported by PCRE2 are described in the pcre2pattern documentation. This document contains a quick-reference summary of the syntax.QUOTING
\x where x is non-alphanumeric is a literal x
\Q...\E treat enclosed characters as literal
ESCAPED CHARACTERS
This table applies to ASCII and Unicode environments. An unrecognized escape sequence causes an error.\a alarm, that is, the BEL character (hex 07)
\cx "control-x", where x is any ASCII printing character
\e escape (hex 1B)
\f form feed (hex 0C)
\n newline (hex 0A)
\r carriage return (hex 0D)
\t tab (hex 09)
\0dd character with octal code 0dd
\ddd character with octal code ddd, or backreference
\o{ddd..} character with octal code ddd..
\N{U+hh..} character with Unicode code point hh.. (Unicode mode only)
\xhh character with hex code hh
\x{hh..} character with hex code hh..
\U the character "U"
\uhhhh character with hex code hhhh
\u{hh..} character with hex code hh.. but only for EXTRA_ALT_BSUX
CHARACTER TYPES
. any character except newline;
in dotall mode, any character whatsoever
\C one code unit, even in UTF mode (best avoided)
\d a decimal digit
\D a character that is not a decimal digit
\h a horizontal white space character
\H a character that is not a horizontal white space character
\N a character that is not a newline
\p{ xx} a character with the xx property
\P{ xx} a character without the xx property
\R a newline sequence
\s a white space character
\S a character that is not a white space character
\v a vertical white space character
\V a character that is not a vertical white space character
\w a "word" character
\W a "non-word" character
\X a Unicode extended grapheme cluster
GENERAL CATEGORY PROPERTIES FOR \p and \P
C Other
Cc Control
Cf Format
Cn Unassigned
Co Private use
Cs Surrogate
L Letter
Ll Lower case letter
Lm Modifier letter
Lo Other letter
Lt Title case letter
Lu Upper case letter
Lc Ll, Lu, or Lt
L& Ll, Lu, or Lt
M Mark
Mc Spacing mark
Me Enclosing mark
Mn Non-spacing mark
N Number
Nd Decimal number
Nl Letter number
No Other number
P Punctuation
Pc Connector punctuation
Pd Dash punctuation
Pe Close punctuation
Pf Final punctuation
Pi Initial punctuation
Po Other punctuation
Ps Open punctuation
S Symbol
Sc Currency symbol
Sk Modifier symbol
Sm Mathematical symbol
So Other symbol
Z Separator
Zl Line separator
Zp Paragraph separator
Zs Space separator
PCRE2 SPECIAL CATEGORY PROPERTIES FOR \p and \P
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, VT, FF, CR
Xuc Univerally-named character: one that can be
represented by a Universal Character Name
Xwd Perl word: property Xan or underscore
BINARY PROPERTIES FOR \p AND \P
Unicode defines a number of binary properties, that is, properties whose only values are true or false. You can obtain a list of those that are recognized by \p and \P, along with their abbreviations, by running this command:pcre2test -LP
SCRIPT MATCHING WITH \p AND \P
Many script names and their 4-letter abbreviations are recognized in \p{sc:...} or \p{scx:...} items, or on their own with \p (and also \P of course). You can obtain a list of these scripts by running this command:pcre2test -LS
THE BIDI_CLASS PROPERTY FOR \p AND \P
\p{Bidi_Class:<class>} matches a character with the given class
\p{BC:<class>} matches a character with the given class
AL Arabic letter
AN Arabic number
B paragraph separator
BN boundary neutral
CS common separator
EN European number
ES European separator
ET European terminator
FSI first strong isolate
L left-to-right
LRE left-to-right embedding
LRI left-to-right isolate
LRO left-to-right override
NSM non-spacing mark
ON other neutral
PDF pop directional format
PDI pop directional isolate
R right-to-left
RLE right-to-left embedding
RLI right-to-left isolate
RLO right-to-left override
S segment separator
WS which space
CHARACTER CLASSES
[...] 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
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 \w
xdigit hexadecimal digit
QUANTIFIERS
? 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
ANCHORS AND SIMPLE ASSERTIONS
\b word boundary
\B not a word boundary
^ start of subject
also after an internal newline in multiline mode
(after any newline if PCRE2_ALT_CIRCUMFLEX is set)
\A start of subject
$ end of subject
also before newline at end of subject
also before internal newline in multiline mode
\Z end of subject
also before newline at end of subject
\z end of subject
\G first matching position in subject
REPORTED MATCH POINT SETTING
\K set reported start of match
ALTERNATION
expr|expr|expr...
CAPTURING
(...) capture group
(?<name>...) named capture group (Perl)
(?'name'...) named capture group (Perl)
(?P<name>...) named capture group (Python)
(?:...) non-capture group
(?|...) non-capture group; reset group numbers for
capture groups in each alternative
ATOMIC GROUPS
(?>...) atomic non-capture group
(*atomic:...) atomic non-capture group
COMMENT
(?#....) comment (not nestable)
OPTION SETTING
Changes of these options within a group are automatically cancelled at the end of the group.(?i) caseless
(?J) allow duplicate named groups
(?m) multiline
(?n) no auto capture
(?s) single line (dotall)
(?U) default ungreedy (lazy)
(?x) extended: ignore white space except in classes
(?xx) as (?x) but also ignore space and tab in classes
(?-...) unset option(s)
(?^) unset imnsx options
(*LIMIT_DEPTH=d) set the backtracking limit to d
(*LIMIT_HEAP=d) set the heap size limit to d * 1024 bytes
(*LIMIT_MATCH=d) set the match limit to d
(*NOTEMPTY) set PCRE2_NOTEMPTY when matching
(*NOTEMPTY_ATSTART) set PCRE2_NOTEMPTY_ATSTART when matching
(*NO_AUTO_POSSESS) no auto-possessification (PCRE2_NO_AUTO_POSSESS)
(*NO_DOTSTAR_ANCHOR) no .* anchoring (PCRE2_NO_DOTSTAR_ANCHOR)
(*NO_JIT) disable JIT optimization
(*NO_START_OPT) no start-match optimization (PCRE2_NO_START_OPTIMIZE)
(*UTF) set appropriate UTF mode for the library in use
(*UCP) set PCRE2_UCP (use Unicode properties for \d etc)
NEWLINE CONVENTION
These are recognized only at the very start of the pattern or after option settings with a similar syntax.(*CR) carriage return only
(*LF) linefeed only
(*CRLF) carriage return followed by linefeed
(*ANYCRLF) all three of the above
(*ANY) any Unicode newline sequence
(*NUL) the NUL character (binary zero)
WHAT \R MATCHES
These are recognized only at the very start of the pattern or after option setting with a similar syntax.(*BSR_ANYCRLF) CR, LF, or CRLF
(*BSR_UNICODE) any Unicode newline sequence
LOOKAHEAD AND LOOKBEHIND ASSERTIONS
(?=...) )
(*pla:...) ) positive lookahead
(*positive_lookahead:...) )
(?!...) )
(*nla:...) ) negative lookahead
(*negative_lookahead:...) )
(?<=...) )
(*plb:...) ) positive lookbehind
(*positive_lookbehind:...) )
(?<!...) )
(*nlb:...) ) negative lookbehind
(*negative_lookbehind:...) )
NON-ATOMIC LOOKAROUND ASSERTIONS
These assertions are specific to PCRE2 and are not Perl-compatible.(?*...) )
(*napla:...) ) synonyms
(*non_atomic_positive_lookahead:...) )
(?<*...) )
(*naplb:...) ) synonyms
(*non_atomic_positive_lookbehind:...) )
SCRIPT RUNS
(*script_run:...) ) script run, can be backtracked into
(*sr:...) )
(*atomic_script_run:...) ) atomic script run
(*asr:...) )
BACKREFERENCES
\n reference by number (can be ambiguous)
\gn reference by number
\g{n} reference by number
\g+n relative reference by number (PCRE2 extension)
\g-n relative reference by number
\g{+n} relative reference by number (PCRE2 extension)
\g{-n} relative reference by number
\k<name> reference by name (Perl)
\k'name' reference by name (Perl)
\g{name} reference by name (Perl)
\k{name} reference by name (.NET)
(?P=name) reference by name (Python)
SUBROUTINE REFERENCES (POSSIBLY RECURSIVE)
(?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)
\g<name> call subroutine by name (Oniguruma)
\g'name' call subroutine by name (Oniguruma)
\g<n> call subroutine by absolute number (Oniguruma)
\g'n' call subroutine by absolute number (Oniguruma)
\g<+n> call subroutine by relative number (PCRE2 extension)
\g'+n' call subroutine by relative number (PCRE2 extension)
\g<-n> call subroutine by relative number (PCRE2 extension)
\g'-n' call subroutine by relative number (PCRE2 extension)
CONDITIONAL PATTERNS
(?(condition)yes-pattern)
(?(condition)yes-pattern|no-pattern)
(?(n) absolute reference condition
(?(+n) relative reference condition
(?(-n) relative reference condition
(?(<name>) named reference condition (Perl)
(?('name') named reference condition (Perl)
(?(name) named reference condition (PCRE2, deprecated)
(?(R) overall recursion condition
(?(Rn) specific numbered group recursion condition
(?(R&name) specific named group recursion condition
(?(DEFINE) define groups for reference
(?(VERSION[>]=n.m) test PCRE2 version
(?(assert) assertion condition
BACKTRACKING CONTROL
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:(*ACCEPT) force successful match
(*FAIL) force backtrack; synonym (*F)
(*MARK:NAME) set name to be passed back; synonym (*:NAME)
(*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
CALLOUTS
(?C) callout (assumed number 0)
(?Cn) callout with numerical data n
(?C"text") callout with string data
SEE ALSO
pcre2pattern(3), pcre2api(3), pcre2callout(3), pcre2matching(3), pcre2(3).AUTHOR
Philip Hazel Retired from University Computing Service Cambridge, England.
REVISION
Last updated: 12 January 2022 Copyright (c) 1997-2022 University of Cambridge.
12 January 2022 | PCRE2 10.40 |