34.2.1.2 Character Classes

Here is a table of the classes you can use in a character alternative, in Emacs 21, 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’.