Regex: List of Metacharacters

Positional

Metacharacter	Description
^	Beginning of line
$	End of line
\A	Beginning of string
\z	End of string
\Z	End of string (excluding line endings)
\b	Word boundaries
\B	Non-word boundaries

• The ^ and $ are used as “beginning and end of line” but this is the case in multiline mode (usually this is the default). In single-line mode, it is the beginning or end of the entire string.

Special characters

Metacharacter	Description
\	Escape
\t	Tab
\n	Newline (CR)
\r	Newline (LF)
\f	New page
\d	Digits
\D	Non-digits
\s	Whitespace (space, tab, neewline and new page)
\S	Non-whitespace
\w	Word (alphanumeric characters plus ”_“)
\W	Non-word

Wildcards and repetition (quantity specifiers)

• Default: Match the longest part that matches the condition. Preference is given to matching the entire pattern.
• Lazy: Match the shortest part that matches the condition.
• Greedy: Match the longest part that matches the condition. No preference is given to matching the entire pattern.

Default	Lazy	Greedy	Description
.			Any one character (excluding line feed code)
*	*?	*+	0 or more occurrences of the preceding item
+	+?	++	1 or more occurrences of the preceding item
?	??	?+	0 or 1 occurrences of the preceding item
{n}	{n}?	{n}+	n occurrences of the preceding item
{n,}	{n,}?	{n,}+	n or more occurrences of the preceding item
{n,m}	{n,m}?	{n,m}+	n or more and not more than m occurrences of the preceding item

e.g. abcXdefX

	Regex	Result
Default	^.*X	abcXdefX
Lazy	^.*?X	abcX
Greedy	^.*+X	Not match.*
Greedy	^.*+	abcXdefX

(*) ^.*+ matches all “abcXdefX”, so the last X does not match.

Select from candidates

Metacharacter	Description
()	Blocking
|	Or (strings)
[]	Or (one character)

e.g. |

Metacharacter	Description
abc|mno|xyz	Simple abc, mno, or xyz
abc.*X|m+o|xy?z	Include metachar in candidates abcXXX, mXo, xz, etc.
(abc|mno|xyz)X	Combine with other strings abcX, mnoX, or xyzX
(abc|mno|xyz)*	Combine with quantity specifiers abcabc, mnoabcxyz, etc.

e.g. []

Metacharacter	Description
[abc]	Simple (a, b, or c)
[^abc]	Negation (Other than a, b, c)
[a-z]	Range (lowercase)
[A-Z]	Range (uppercase)
[0-9]	Range (digits)
[a-zA-Z]	Or (a to z or A to Z)
[a-z&&[d-f]]	And (a to z and d to f)
[a-z&&[^d-f]]	Subtraction (a to z excluding d to f)

Lookahead and Lookbehind

Meta	Description	e.g.	Description
?=	Positive lookahead	foo(?=bar)	Matches “foo” followed by “bar”.
?!	Negative lookahead	foo(?!bar)	Matches “foo” not followed by “bar”.
?<=	Positive lookbehind	(?<=bar)foo	Matches “foo” preceded by “bar”.
?<!	Negative lookbehind	(?<!bar)foo	Matches “foo” not preceded by “bar”.