Regular Expressions Cheat Sheet
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1Regular Expressions Cheat Sheet
by
Dave Child (DaveChild)
via
Anchors
Assertions
Groups and Ranges
^
Start of string, or start of line in multi-line
?=
Lookahead assertion
.
Any character except new line (\n)
pattern
?!
Negative lookahead
(a|b)
a or b
\A
Start of string
?<=
Lookbehind assertion
(...)
Group
$
End of string, or end of line in multi-line
?!= or ?<!
Negative lookbehind
(?:...)
Passive (non-c a pt u ring) group
pattern
?>
Once-only Subexp r ession
[abc]
Range (a or b or c)
\Z
End of string
?()
Condition [if then]
[^abc]
Not (a or b or c)
\b
Word boundary
?()|
Condition [if then else]
[a-q]
Lower case letter from a to q
\B
Not word boundary
?#
Comment
[A-Q]
Upper case letter from A to Q
\<
Start of word
[0-7]
Digit from 0 to 7
\>
End of word
Quanti f iers
\x
Group/ s ub p attern number " x "
*
0 or more
{3}
Exactly 3
Ranges are inclusive.
Character Classes
+
1 or more
{3,}
3 or more
\c
Control character
Pattern Modifiers
?
0 or 1
{3,5}
3, 4 or 5
\s
White space
Add a ? to a quantifier to make it ungreedy.
g
Global match
\S
Not white space
i *
Case-i n se n sitive
\d
Digit
Escape Sequences
m *
Multiple lines
\D
Not digit
\
Escape following character
s *
Treat string as single line
\w
Word
\Q
Begin literal sequence
x *
Allow comments and whitespace in
\W
Not word
pattern
\E
End literal sequence
\x
Hexade c imal digit
e *
Evaluate replac e ment
" E sc a pi n g" is a way of treating characters
\O
Octal digit
which have a special meaning in regular
U *
Ungreedy pattern
expres s ions literally, rather than as special
* PCRE modifier
POSIX
charac t ers.
[:upper:]
Upper case letters
String Replac e ment
Common Metach a ra c ters
[:lower:]
Lower case letters
$n
nth non-pa s sive group
^
[
.
$
[:alpha:]
All letters
$2
" x yz " in /^(abc ( xy z ))$/
{
*
(
\
[:alnum:]
Digits and letters
$1
" x yz " in /^(?:a b c) ( xyz)$/
+
)
|
?
[:digit:]
Digits
$`
Before matched string
<
>
[:xdigit:]
Hexade c imal digits
$'
After matched string
The escape character is usually \
[:punct:]
Punctu a tion
$+
Last matched string
[:blank:]
Space and tab
$&
Entire matched string
Special Characters
[:space:]
Blank characters
Some regex implem e nt a tions use \ instead of $.
\n
New line
[:cntrl:]
Control characters
\r
Carriage return
[:graph:]
Printed characters
\t
Tab
[:print:]
Printed characters and spaces
\v
Vertical tab
[:word:]
Digits, letters and underscore
\f
Form feed
\xxx
Octal character xxx
\xhh
Hex character hh
By Dave Child (DaveChild)
Published 19th October, 2011.
Sponsored by
Last updated 12th May, 2016.
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