.Net: Cheat Sheet for Regular Expression

Regular Expressions Cheat Sheet

 

^	The pattern has to appear at the beginning of a string.	^cat matches any string that begins with cat
$	The pattern has to appear at the end of a string.	cat$ matches any string that ends with cat
.	Matches any character.	cat. matches catT and cat2 but not catty
[]	Bracket expression. Matches one of any characters enclosed.	gr[ae]y matches gray or grey
[^]	Negates a bracket expression. Matches one of any characters EXCEPT those enclosed.	1[^02] matches 13 but not 10 or 12
[-]	Range. Matches any characters within the range.	[1-9] matches any single digit EXCEPT 0
?	Preceeding item must match one or zero times.	colou?r matches color or colour but not colouur
+	Preceeding item must match one or more times.	be+ matches be or bee but not b
*	Preceeding item must match zero or more times.	be* matches b or be or beeeeeeeeee
()	Parentheses. Creates a substring or item that metacharacters can be applied to	a(bee)?t matches at or abeet but not abet
{n}	Bound. Specifies exact number of times for the preceeding item to match.	[0-9]{3} matches any three digits
{n,}	Bound. Specifies minimum number of times for the preceeding item to match.	[0-9]{3,} matches any three or more digits
{n,m}	Bound. Specifies minimum and maximum number of times for the preceeding item to match.	[0-9]{3,5} matches any three, four, or five digits
|	Alternation. One of the alternatives has to match.	July (first|1st|1) will match July 1st but not July 2

 

POSIX Character Classes

 

[:alnum:]	alphanumeric character	[[:alnum:]]{3} matches any three letters or numbers, like 7Ds
[:alpha:]	alphabetic character, any case	[[:alpha:]]{5} matches five alphabetic characters, any case, like aBcDe
[:blank:]	space and tab	[[:blank:]]{3,5} matches any three, four, or five spaces and tabs
[:digit:]	digits	[[:digit:]]{3,5} matches any three, four, or five digits, like 3, 05, 489
[:lower:]	lowercase alphabetics	[[:lower:]] matches a but not A
[:punct:]	punctuation characters	[[:punct:]] matches ! or . or , but not a or 3
[:space:]	all whitespace characters, including newline and carriage return	[[:space:]] matches any space, tab, newline, or carriage return
[:upper:]	uppercase alphabetics	[[:upper:]] matches A but not a

 

Perl-Style Meta characters

 

//	Default delimiters for pattern	/colou?r/ matches color or colour
i	Append to pattern to specify a case insensitive match	/colou?r/i matches COLOR or Colour
\b	A word boundary, the spot between word (\w) and non-word (\W) characters	/\bfred\b/i matches Fred but not Alfred or Frederick
\B	A non-word boundary	/fred\B/i matches Frederick but not Fred
\d	A single digit character	/a\db/i matches a2b but not acb
\D	A single non-digit character	/a\Db/i matches aCb but not a2b
\n	The newline character. (ASCII 10)	/\n/ matches a newline
\r	The carriage return character. (ASCII 13)	/\r/ matches a carriage return
\s	A single whitespace character	/a\sb/ matches a b but not ab
\S	A single non-whitespace character	/a\Sb/ matches a2b but not a b
\t	The tab character. (ASCII 9)	/\t/ matches a tab.
\w	A single word character – alphanumeric and underscore	/\w/ matches 1 or _ but not ?
\W	A single non-word character	/a\Wb/i matches a!b but not a2b

 

 

Reference: Click here

 

Happy expression-ing J

 

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