Regex Cheat Sheet

Matching Characters

[abc]	Matches any single character: a, b, or c
[^abc]	Matches any single character except: a, b, or c. “^” is only valid as the first character
[a-g]	Matches any single character in the range a-g
[^a-g]	Matches any single character NOT in the range a-g
[H-N]	Matches any single character in the range H-N
[0-9]	Matches any single digit in the range 0-9
[a-gH-N]	Matches any single character in the range a-g or H-N
Wildcards:
.	[^\n\r], matches any character except newline
\s	whitespace character, i.e., newline, tab, space, etc.
\S	[^\s], any non-whitespace character
\d	digit: [0-9]
\D	[^\d], any non-digit character
\w	word character: [0-9A-Za-z_]
\W	[^\w], any non-word character

Matching Groups

(a	b)
(…)	Capturing group
(?:…)	Non-capturing group
(?…) or (?’name’…)	Named capturing group (name can be customized)
(?(condition)true_regex	false_regex)

group(0) is used to get the entire match result. group(>0) can get sub-capturing groups from the entire match result.

Note: Named capturing groups are supported in Java 1.7+ (using the group method with name as parameter). JavaScript and Python temporarily do not support named capturing groups in some environments (though modern versions do).

Frequency Range

{3}	Preceding item appears exactly 3 times, equivalent to {3,3}
{3,6}	Preceding item appears between 3 and 6 times
{3,}	Preceding item appears at least 3 times
{0,6}	Preceding item appears at most 6 times
Wildcards:
*	{0,} Zero or more
+	{1,} One or more
?	{0,1} Zero or one
\w*	Greedy mode
\w*?	Non-greedy (lazy) mode

Anchors

^	Start of string
$	End of string
\b	Boundary, word boundary
\B	Non-word boundary
Lookaround Assertions:
(?=exp)	Positive lookahead (suffix is exp)
(?<=exp)	Positive lookbehind (prefix is exp)
(?!exp)	Negative lookahead (suffix is NOT exp)
(?<!exp)	Negative lookbehind (prefix is NOT exp)

\b(\w+)\b is equivalent to (?<=\W?)(\w+)(?=\W?)