Regex 官方文档

Anchors

Anchros

^
Start of string, or start of line in multi-line pattern
\>
End of word
\<
Start of word
\A
Start of string
\b
Word boundary
\Z
End of string
$
End of string, or end of line in multi-line pattern

Quantifiers

Quantifiers

?
0 or 1
{,5}
5 or less
{3,}
3 or more
{3,5}
3, 4 or 5
{3}
Exactly 3
*
0 or more
+
1 or more

Character

Character Classes

\c
Control character
\d
Digit
\O
Octal digit
\s
White space
\w
Word
\x
Hexade-cimal digit

Special

\f
Form feed
\n
New line
\r
Carriage return
\t
Tab
\v
Vertical tab
\xhh
Hex character hh
\xxx
Octal character xxx

Examples

Metacharacter

^abc
abc, abcdefg, abc123, ...
(abc){2}
abcabc
a.c
abc, aac, acc, adc, aec, ...
a[bB]c
abc, aBc
a\sc
a c
ab?c
ac, abc
ab{2}c
abbc
ab*c
ac, abc, abbc, abbbc, ...
ab+c
abc, abbc, abbbc, ...
abc$
abc, endsinabc, 123abc, ...
bill|ted
ted, bill

Sample

(^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$)
Any number from 1 to 50 inclusive
((?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,15})
8 to 15 character string with at least one upper case letter, one lower case letter, and one digit (useful for passwords).
([^\s]+(?=\.(jpg|gif|png))\.\2)
jpg, gif or png image
([A-Za-z0-9-]+)
Letters, numbers and hyphens
(\<(/?[^\>]+)\>)
HTML Tag
(\d{1,2}\/\d{1,2}\/\d{4})
Date (e.g. 21/3/2006)
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6})
Email addresses
(#?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})?)
Valid hexadecimal colour code

POSIX

POSIX

[:alnum:]
Digits and letters
[:alpha:]
All letters
[:blank:]
Space and tab
[:cntrl:]
Control characters
[:digit:]
Digits
[:graph:]
Printed characters
[:lower:]
Lower case letters
[:print:]
Printed characters and spaces
[:punct:]
Punctu-ation
[:space:]
Blank characters
[:upper:]
Upper case letters
[:word:]
Digits, letters and underscore
[:xdigit:]
Hexade-cimal digits

Groups

Groups and Ranges

.
Any character except new line (\n)
(?:...)
Passive (non-c-apt-uring) group
(...)
Group
(a|b)
a or b
[^abc]
Not a or b or c
[0-7]
Digit from 0 to 7
[a-q]
Letter from a to q
[abc]
Range (a or b or c)

Modifiers

Modifiers

e
Evaluate replac-ement
g
Global match
i
Case-i-nse-nsitive
m
Multiple lines
s
Treat string as single line
U
Ungreedy pattern
x
Allow comments and white space in pattern

String

Replacement

$`
Before matched string
$'
After matched string
$&
Entire matched string
$+
Last matched string
$1
"-xyz-" in /^(?:a-bc)-(xyz)$/
$2
"-xyz-" in /^(abc-(xy-z))$/
$n
nth non-pa-ssive group

Assertions

Assertions

?!
Negative lookahead
?!= or ?<!
Negative lookbehind
?()
Condition [if then]
?()|
Condition [if then else]
?>
Once-only Subexp-ression
?<=
Lookbehind assertion
?#
Comment
?=
Lookahead assertion