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