34.3.1.2 Character Classes

Here is a table of the classes you can use in a character alternative, and what they mean:

`[:ascii:]'

This matches any ASCII (unibyte) character.

`[:alnum:]'

This matches any letter or digit. (At present, for multibyte characters, it matches anything that has word syntax.)

`[:alpha:]'

This matches any letter. (At present, for multibyte characters, it matches anything that has word syntax.)

`[:blank:]'

This matches space and tab only.

`[:cntrl:]'

This matches any ASCII control character.

`[:digit:]'

This matches `0' through `9'. Thus, `[-+[:digit:]]' matches any digit, as well as `+' and “-”.

`[:graph:]'

This matches graphic characters—everything except ASCII control characters, space, and the delete character.

`[:lower:]'

This matches any lower-case letter, as determined by the current case table (see Case Tables).

`[:nonascii:]'

This matches any non-ASCII (multibyte) character.

`[:print:]'

This matches printing characters—everything except ASCII control characters and the delete character.

`[:punct:]'

This matches any punctuation character. (At present, for multibyte characters, it matches anything that has non-word syntax.)

`[:space:]'

This matches any character that has whitespace syntax (see Syntax Class Table).

`[:upper:]'

This matches any upper-case letter, as determined by the current case table (see Case Tables).

`[:word:]'

This matches any character that has word syntax (see Syntax Class Table).

`[:xdigit:]'

This matches the hexadecimal digits: `0' through `9', “a” through “f” and “A” through “F”.