1. Regular Expressions Cheat Sheet
by Dave Child (DaveChild) via cheatography.com/1/cs/5/
Regular Expressions Anchors
Regular Expressions Quantifiers
Regular Expressions Groups and Ranges
^
Start of string, or start of line in multi-line pattern
*
0 or more
.
Any character except new line (n)
A
Start of string
+
1 or more
(a|b)
a or b
$
End of string, or end of line in multi-line pattern
?
0 or 1
(...)
Group
Z
End of string
{3}
Exactly 3
(?:...)
Passive (non-capturing) group
b
Word boundary
{3,}
3 or more
[abc]
Range (a or b or c)
B
Not word boundary
{3,5}
3, 4 or 5
[^abc]
Not a or b or c
<
Start of word
Add a ? to a quantifier to make it ungreedy.
[a-q]
Letter from a to q
>
End of word
[A-Q]
Upper case letter from A to Q
Regular Expressions Escape Sequences
[0-7]
Digit from 0 to 7
Regular Expressions Character Classes
Escape following character
n
nth group/subpattern
c
Control character
Q
Begin literal sequence
Ranges are inclusive.
s
White space
E
End literal sequence
S
Not white space
"Escaping" is a way of treating characters which have
Regular Expressions Pattern Modifiers
d
Digit
a special meaning in regular expressions literally,
g
Global match
D
Not digit
rather than as special characters.
i
Case-insensitive
w
Word
m
Multiple lines
W
Not word
s
Treat string as single line
x
Hexadecimal digit
x
Allow comments and white space in pattern
O
Octal digit
e
Evaluate replacement
U
Ungreedy pattern
Regular Expression Common Metacharacters
^
[
.
$
{
*
(
+
Regular Expressions POSIX
)
|
?
[:upper:]
Upper case letters
<
>
[:lower:]
Lower case letters
The escape character is usually the backslash - .
[:alpha:]
All letters
[:alnum:]
Digits and letters
[:digit:]
Digits
[:xdigit:]
Hexadecimal digits
[:punct:]
Punctuation
[:blank:]
Space and tab
[:space:]
Blank characters
[:cntrl:]
Control characters
[:graph:]
Printed characters
[:print:]
Printed characters and spaces
[:word:]
Digits, letters and underscore
Regular Expressions Special Characters
n
New line
r
Carriage return
t
Tab
v
Vertical tab
f
Form feed
xxx
Octal character xxx
xhh
Regular Expressions String Replacement
$n
nth non-passive group
$2
"xyz" in /^(abc(xyz))$/
$1
"xyz" in /^(?:abc)(xyz)$/
$`
Before matched string
$'
After matched string
$+
Last matched string
$&
Entire matched string
Hex character hh
Some regex implementations use instead of $.
Regular Expressions Assertions
?=
Lookahead assertion
?!
Negative lookahead
?<=
Lookbehind assertion
?!= or ?<!
Negative lookbehind
?>
Once-only Subexpression
?()
Condition [if then]
?()|
Condition [if then else]
?#
Comment
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This cheat sheet was published on 19th October, 2011
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