RE2 语法（待译）

This page lists the regular expression syntax accepted by RE2. 本页列举RE2支持的正则表达式语法
It also lists syntax accepted by PCRE, PERL, and VIM. 也列举PCRE、PERL和VIM支持的语法
Grayed out expressions are not supported by RE2. 灰色的表达式是RE2不支持的
Single characters: 单字符：
.	any character, possibly including newline (s=true) 任何字符，可能包括新行（s=true的条件下）
[xyz]	character class
[^xyz]	negated character class
\d	Perl character class
\D	negated Perl character class
[[:alpha:]]	ASCII character class
[[:^alpha:]]	negated ASCII character class
\pN	Unicode character class (one-letter name)
\p{Greek}	Unicode character class
\PN	negated Unicode character class (one-letter name)
\P{Greek}	negated Unicode character class
Composites:
xy	x followed by y
x|y	x or y (prefer x)
Repetitions:
x*	zero or more x, prefer more
x+	one or more x, prefer more
x?	zero or one x, prefer one
x{n,m}	n or n+1 or ... or m x, prefer more
x{n,}	n or more x, prefer more
x{n}	exactly n x
x*?	zero or more x, prefer fewer
x+?	one or more x, prefer fewer
x??	zero or one x, prefer zero
x{n,m}?	n or n+1 or ... or m x, prefer fewer
x{n,}?	n or more x, prefer fewer
x{n}?	exactly n x
x{}	(≡ x*) (NOT SUPPORTED) VIM
x{-}	(≡ x*?) (NOT SUPPORTED) VIM
x{-n}	(≡ x{n}?) (NOT SUPPORTED) VIM
x=	(≡ x?) (NOT SUPPORTED) VIM
Implementation restriction: The counting forms x{n,m}, x{n,}, and x{n}
reject forms that create a minimum or maximum repetition count above 1000.
Unlimited repetitions are not subject to this restriction.
Possessive repetitions:
x*+	zero or more x, possessive (NOT SUPPORTED)
x++	one or more x, possessive (NOT SUPPORTED)
x?+	zero or one x, possessive (NOT SUPPORTED)
x{n,m}+	n or ... or m x, possessive (NOT SUPPORTED)
x{n,}+	n or more x, possessive (NOT SUPPORTED)
x{n}+	exactly n x, possessive (NOT SUPPORTED)
Grouping:
(re)	numbered capturing group (submatch)
(?Pre)	named & numbered capturing group (submatch)
(?re)	named & numbered capturing group (submatch) (NOT SUPPORTED)
(?'name're)	named & numbered capturing group (submatch) (NOT SUPPORTED)
(?:re)	non-capturing group
(?flags)	set flags within current group; non-capturing
(?flags:re)	set flags during re; non-capturing
(?#text)	comment (NOT SUPPORTED)
(?|x|y|z)	branch numbering reset (NOT SUPPORTED)
(?>re)	possessive match of re (NOT SUPPORTED)
re@>	possessive match of re (NOT SUPPORTED) VIM
%(re)	non-capturing group (NOT SUPPORTED) VIM
Flags:
i	case-insensitive (default false)
m	multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)
s	let . match \n (default false)
U	ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false)
Flag syntax is xyz (set) or -xyz (clear) or xy-z (set xy, clear z).
Empty strings:
^	at beginning of text or line (m=true)
$	at end of text (like \z not \Z) or line (m=true)
\A	at beginning of text
\b	at ASCII word boundary (\w on one side and \W, \A, or \z on the other)
\B	not at ASCII word boundary
\G	at beginning of subtext being searched (NOT SUPPORTED) PCRE
\G	at end of last match (NOT SUPPORTED) PERL
\Z	at end of text, or before newline at end of text (NOT SUPPORTED)
\z	at end of text
(?=re)	before text matching re (NOT SUPPORTED)
(?!re)	before text not matching re (NOT SUPPORTED)
(?<=re)	after text matching re (NOT SUPPORTED)
(?	after text not matching re (NOT SUPPORTED)
re&	before text matching re (NOT SUPPORTED) VIM
re@=	before text matching re (NOT SUPPORTED) VIM
re@!	before text not matching re (NOT SUPPORTED) VIM
re@<=	after text matching re (NOT SUPPORTED) VIM
re@	after text not matching re (NOT SUPPORTED) VIM
\zs	sets start of match (= \K) (NOT SUPPORTED) VIM
\ze	sets end of match (NOT SUPPORTED) VIM
\%^	beginning of file (NOT SUPPORTED) VIM
\%$	end of file (NOT SUPPORTED) VIM
\%V	on screen (NOT SUPPORTED) VIM
\%#	cursor position (NOT SUPPORTED) VIM
\%'m	mark m position (NOT SUPPORTED) VIM
\%23l	in line 23 (NOT SUPPORTED) VIM
\%23c	in column 23 (NOT SUPPORTED) VIM
\%23v	in virtual column 23 (NOT SUPPORTED) VIM
Escape sequences:
\a	bell (≡ \007)
\f	form feed (≡ \014)
\t	horizontal tab (≡ \011)
\n	newline (≡ \012)
\r	carriage return (≡ \015)
\v	vertical tab character (≡ \013)
\*	literal *, for any punctuation character *
\123	octal character code (up to three digits)
\x7F	hex character code (exactly two digits)
\x{10FFFF}	hex character code
\C	match a single byte even in UTF-8 mode
\Q...\E	literal text ... even if ... has punctuation
\1	backreference (NOT SUPPORTED)
\b	backspace (NOT SUPPORTED) (use \010)
\cK	control char ^K (NOT SUPPORTED) (use \001 etc)
\e	escape (NOT SUPPORTED) (use \033)
\g1	backreference (NOT SUPPORTED)
\g{1}	backreference (NOT SUPPORTED)
\g{+1}	backreference (NOT SUPPORTED)
\g{-1}	backreference (NOT SUPPORTED)
\g{name}	named backreference (NOT SUPPORTED)
\g	subroutine call (NOT SUPPORTED)
\g'name'	subroutine call (NOT SUPPORTED)
\k	named backreference (NOT SUPPORTED)
\k'name'	named backreference (NOT SUPPORTED)
\lX	lowercase X (NOT SUPPORTED)
\ux	uppercase x (NOT SUPPORTED)
\L...\E	lowercase text ... (NOT SUPPORTED)
\K	reset beginning of $0 (NOT SUPPORTED)
\N{name}	named Unicode character (NOT SUPPORTED)
\R	line break (NOT SUPPORTED)
\U...\E	upper case text ... (NOT SUPPORTED)
\X	extended Unicode sequence (NOT SUPPORTED)
\%d123	decimal character 123 (NOT SUPPORTED) VIM
\%xFF	hex character FF (NOT SUPPORTED) VIM
\%o123	octal character 123 (NOT SUPPORTED) VIM
\%u1234	Unicode character 0x1234 (NOT SUPPORTED) VIM
\%U12345678	Unicode character 0x12345678 (NOT SUPPORTED) VIM
Character class elements:
x	single character
A-Z	character range (inclusive)
\d	Perl character class
[:foo:]	ASCII character class foo
\p{Foo}	Unicode character class Foo
\pF	Unicode character class F (one-letter name)
Named character classes as character class elements:
[\d]	digits (≡ \d)
[^\d]	not digits (≡ \D)
[\D]	not digits (≡ \D)
[^\D]	not not digits (≡ \d)
[[:name:]]	named ASCII class inside character class (≡ [:name:])
[^[:name:]]	named ASCII class inside negated character class (≡ [:^name:])
[\p{Name}]	named Unicode property inside character class (≡ \p{Name})
[^\p{Name}]	named Unicode property inside negated character class (≡ \P{Name})
Perl character classes (all ASCII-only):
\d