Regular Expressions Cheat Sheet

^ The pattern has to appear at the beginning of a line.	^cat matches any string that begins with cat
$ The pattern has to appear at the end of a line.	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
[:xdigit:] Hexade­cimal digits
[:cntrl:] Control characters
[:graph:] Printed characters
[:print:] Printed characters and spaces
[:word:] Digits, letters and underscore

 

Perl-Style Metacharacters

// 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