33.3.1.2 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 character (codes 0–127).

‘[: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). If case-fold-search is non-nil, this also matches any upper-case letter.

‘[:multibyte:]’

This matches any multibyte character (see Text Representations).

‘[:nonascii:]’

This matches any non-ASCII 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).

‘[:unibyte:]’

This matches any unibyte character (see Text Representations).

‘[:upper:]’

This matches any upper-case letter, as determined by the current case table (see Case Tables). If case-fold-search is non-nil, this also matches any lower-case letter.

‘[: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’.