snippits/regex-cheetsheet.md

R* Cheatsheet

Modifiers

Symbol	Description
g	Global - search entire string
i	Case-insensitive
m	Multiple lines
s	Treat as single line
x	Allow comments & whitespace
e	Evaluate placement
U	Un-greedy patterns by default

Escape

Symbol	Description
?#	Comment
\	Escape special characters
\Q	Begin literal sequence
\E	End literal sequence

Anchors

Symbol	Description
^	Start of line
$	End of line
\A	Start of string
\Z	End of string
\b	Word boundary
\B	Not word boundary
\<	Start of word
\>	End of word

Characters

Symbol	POSIX	Description
\c	[:cntrl:]	Control character
\S		Not a white space
\s	[:blank:] [:space:]	White space
	[:punct:]	Punctuation
.	[:print:] [:graph:]	Printed Character, with & without spaces
\W		Not a letter
\w	[:alpha:] [:upper:] [:lower:]	Letter
\D		Not a number
\d	[:digit:]	Number
\x	[:xdigit:]	Hexadecimal digit
\O		Octal digit
\n		New line
\r		Carriage return
\t		Tab
\v		Vertical tab
\f		Form feed
\xxx		Octal number "xxx"
\xaa		Hexidecimal "aa"

Repeat

Symbol	Range	Description
	{x}	Exactly x times
	{min,max}	Repeat between min & max times
?	{,1}	0 or 1
* *?	{0,}	0 or many (Adding ? make un-greedy)
+ +?	{1,}	1 or more (Adding ? make un-greedy)

Un-greedy repeaters will take the minimum number of characters required

Group Selectors

Symbol	Description
.	Wildcard/Single character (Except newline)
(abc|123)	abc or 123
(...)	Capture group
(?<name>...)	Named capture group
(?:...)	Group un-captured
[abc]	A or B or C
[^abc]	Not A or B or C
[0-9]	Number between 0 and 9
[a-g]	Lowercase letter between a and g
[A-G]	Uppercase letter between A and G

All selectors are inclusive

Reference Group

Symbol	Description
$n	N'th Group
$\ `	Before matched
$'	After matched
$+	Last match
$&	Entire match

Some regex implementations use \ instead of $.

Assertions

Symbol	Description
?=	Lookahead
?!	Negative lookahead
?<=	Lookbehind
?!= ?<!	Negative lookbehind
?>	Once-only subexpression
?(...)	If condition
?(...) |	If-else condition