Regular Expressions Cheat Sheet

Regular Expression Cheat Sheet

Collected from various sources

Key: Multifarious, java only, p3 only, warning, caution, shared	POSIX	perl php python	java	vbScript	.NET
Anchors
Start of string or start of line in a multi-line pattern	^
Start of string	\A	^
Start of line			^
End of string, or end of line in a multi-line pattern	$
End of string	\Z	$
End of line			$
Word boundary	\b
Not word boundary	\B
Start of Word	\<
End of word	\>
Character Classes
Control Character	\c
White space [\n\r\f\t\v]	\s
Not White space [^\n\r\f\t\v]	\S
Digit [0-9]	\d
Not digit [^0-9]	\D
Word [a-zA-Z0-9_]	\w
Not word [^a-zA-Z0-9_]	\W
Hexadecimal digit	\x
Octal digit	\0
Assertions
Look ahead	?=	(?=...)
Negative look ahead	?!	(?!...)
Look behind	?<=	(?<=...)
Negative look behind	?!= ?<!	(?<!...)
Only once sub expression	?>
Condition [if then]	?()
Condition [if then else]	?()|
Comment	?#
Quantifiers
0 or more	*
1 or more	+
0 or 1	?	?[1]
Match 0 or more times, but a few times as possible		*?
Match 1 or more times, but a few times as possible		+?
Match 0 or 1 times, but as few times as possible		??
Match at least x times, no more than y times, and as few times as possible		{x,y}?
Exactly x	{x}
x or more	{x,}
x, y, z	{x,z}
Escapes
Escape following character	\
Begin literal sequence	\Q
End literal sequence	\E
Special Characters
New Line	\n \x0A \O059
Carriage Return	\r
Tab	\t
Vertical tab	\v
Form feed	\f
Groups and Ranges
Any character except new line	.
a or b	(a|b)
Group	(…)
Passive (non-capturing group)	(?:...)
Range	[abc]
Not range	[^abc]
Letter a – q	[a-q]
Uppercase letter A – Q	[A-Q]
Digit 0 – 7	[0-7]
nth group/sub pattern	\n
Pattern modifiers
Global match	g
Case insensitive	i
Multiple Lines	m
Treat as single line	s
Allow comments and white space in pattern	x
Evaluate replacement	e
Ungreedy pattern	U
String replacement
nth non-passive group	$n
“xyz” in /^(abc(xyz))$/	$2
“xyz” in /^(?:abc)(xyz)$/	$1
Before matched string	$`
After matched string	$’
Last matched string	$+
Entire matched string	$&

Character		Abbr	Hex	Octal	Decimal
Null character		NUL	00	000	0
Form feed	\f	FF	0C	014	12
Line Feed	\n	LF	0A	012	10
Carriage return	\r	CR	0D	015	13
Horizontal Tab	\t	HT	09	011	9
Vertical tab	\v	VT	0B	013	11
Carriage Return Line Feed DOS	\r\n	CRLF

Examples

Sample	RegEx
IP Address	\b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b
Email address	\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b
URL	(((file|gopher|news|nntp|telnet|http|ftp|https|ftps|sftp)://)|(www\.))+(([a-zA-Z0-9\._-]+\.[a-zA-Z]{2,6})|([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(/[a-zA-Z0-9\&%_\./-~-]*)?

Remove Duplicate Lines | ^(.*)(\r?\n\1)+$ Replace with: $1

---

[1] or shortest match