Syntax

^

Beginning of a string

$

End of a string

.

Match any character (except newline) when used outside of a character set

*

Match 0 or more times

+

Match 1 or more times

?

Match 0 or 1 times

|

Alternation

( )

Grouping; "storing"

[ ]

Character set

{ }

Repetition modifier

\

Quote or special

To present a metacharacter as a data character standing for itself, precede it with a backslash '\'.

For example, \. will match the full stop character '.'

a*

0 or more 'a'

a+

1 or more 'a'

a?

0 or 1 'a' (i.e., optional 'a')

a{m}

exactly m 'a'

a{m, }

at least m 'a'

a{m, n}

at least m but at most n 'a'

expr?

shortest match taken from the repetition expression expr (i.e., a*?)

By default it will find the longest match. Use the expr? to find the shortest match.

\t

tab

\n

newline

\r

return (CR)

\xhh

character with hexadecimal code hh

\b

"word" boundary

\B

not a "word" boundary

\w

matches any single character classified as a "word" character (alphanumeric or '_')

\W

matches any non-"word" character

\s

matches any whitespace character (space, tab, newline)

\S

matches any non-whitespace character

\d

matches any digit character (equivalent to [0-9])

\D

matches any non-digit character

[characters]

Matches any of the characters in the sequence

[x-y]

Matches any of the characters from x to y (inclusively)

[\-]

Matches the hyphen character '-'

[\n]

Matches the newline character

[^expr]

Matches any characters except those specified in the expression expr

Other single character denotations with the backslash '\' apply normally too.

[:class:]

Will match any characters from the specified class
Where class can be any of the 

[=name=]

Will match the base character from the specified character or symbolic name.
Where name can be any character or it's 

A base character is a character that ignores case, any accents or unique regional tailoring.

[[:digit:]] will match any digit character.
[[=a=]] will match a, à, á, â, ã, ä, å, A, À, Á, Â, Ã, Ä and Å.

1

[==] [::]

Collation-related bracket symbols

2

\

Escaped characters

3

[ ]

Character set (bracket expression)

4

( )

Grouping

5

* + ? {m,n}

Repetitions

6

Concatenation

7

^ $

Anchoring

8

|

Alternation

 syntax is used in all products.