\s Spaces.
\S Characters that are not spaces.
\d Digits
\D Characters that are not digits.
\w Extended "word" characters
\W Nonword characters.
\i XML 1.0 initial name characters
\I Characters that may not be used as a XML initial name character.
\c XML 1.0 name characters
\C Characters that may not be used in a XML 1.0 name.