Regular Expressions Reference Sheet
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Regular Expression Reference Sheet

Regular Expressions Reference Sheet

CharacterDefinitionExample

^

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 toa(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

CharacterDefinitionExample

[: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 Metacharacters

CharacterDefinitionExample

//

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



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Last modified: May 28 2007.