| [:upper:] | Upper case letters |
| [:lower:] | Lower case letters |
| [:alpha:] | All letters |
| [:alnum:] | Digits and letters |
| [:digit:] | Digits |
| [:xdigit:] | Hexadecimal digits |
| [:punct:] | Punctuation |
| [:blank:] | Space and tab |
| [:space:] | Blank characters |
| [:cntrl:] | Control characters |
| [:graph:] | Printed characters |
| [:print:] | Printed characters and spaces |
| [:word:] | Digits, letters and underscore |