The Unix shell recognises a limited form of regular expressions used with filename substitution:
| Operator | Effect |
|---|---|
| ? | The hook operator specifies any single character. |
| [ ] | boxes enable a single character to be matched against a character lists or character range. |
| [! ] | A compliment box enables a single character not within in a character list or character range to be matched. |
| * | An asterisk specifies zero or more characters to match. |
| ?(pattern-list) | Matches zero or one occurrence of the given patterns. |
| *(pattern-list) | Matches zero or more occurrences of the given patterns. |
| +(pattern-list) | Matches one or more occurrences of the given patterns. |
| @(pattern-list) | Matches exactly one of the given patterns. |
| !(pattern-list) | Matches anything except one of the given patterns. |
Note that the latter five constructs can only be used in bash and only if the extglob option has been enabled using the bash-builtin "shopt".
Some operators behave differently in the shell: The asterisk and hook operators do not not need to follow a previous character in the shell and they exhibit non traditional regular expression behaviour.
Unsupported Constructs: Within the shell, a compliment box is formed using the pling symbol. The shell does not support the use of a careted box for character list exclusion. In the shell, a caret symbol within a box will simply be treated as one of the characters within the character list for matching.
Use in Tools
Tools and languages that utilize this regular expression syntax include:
- Bourne compatible shells
Links
- Bash Pattern Matching at gnu.org