| Character Class |
Meaning |
| [:alpha:] |
Any letter, [A-Za-z] |
| [:upper:] |
Any uppercase letter, [A-Z] |
| [:lower:] |
Any lowercase letter, [a-z] |
| [:digit:] |
Any digit, [0-9] |
| [:alnum:] |
Any alphanumeric character, [A-Za-z0-9] |
| [:xdigit:] |
Any hexadecimal digit, [0-9A-Fa-f] |
| [:space:] |
A tab, new line, vertical tab, form feed, carriage return, or space |
| [:blank:] |
A space or a tab. |
| [:print:] |
Any printable character |
| [:punct:] |
Any punctuation character: ! ' # S % & ' ( ) * + , - . / : ; < = > ? @ [ / ] ^ _ { | } ~ |
| [:graph:] |
Any character defined as a printable character except those defined as part of the space character class |
| [:word:] |
Continuous string of alphanumeric characters and underscores. |
| [:ascii:] |
ASCII characters, in the range: 0-127 |
| [:cntrl:] |
Any character not part of the character classes: [:upper:], [:lower:], [:alpha:], [:digit:], [:punct:], [:graph:], [:print:], [:xdigit:] |