Regular Expressions/Shell Regular Expressions
The Unix shell recognises a glob syntax for use with filename substitution. With the extglob extension of ksh and bash, it is equivalent to a basic form of regular expression in expressiveness.
| 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. A non-standard equivalent, supported by GNU bash, is the caret syntax [^ ]. |
| * | An asterisk specifies zero or more characters to match. |
| ?(pattern-list) | Matches zero or one occurrence of the given patterns. extglob extension. |
| *(pattern-list) | Matches zero or more occurrences of the given patterns. extglob extension. |
| +(pattern-list) | Matches one or more occurrences of the given patterns. extglob extension. |
| @(pattern-list) | Matches exactly one of the given patterns. extglob extension. |
| !(pattern-list) | Matches anything except one of the given patterns. extglob extension. |
Differences from common regular expressions are:
- The asterisk and hook operators mean different things.
- The compliment bow is formed using the exclamation mark (!) in the POSIX standard, not a caret (^). Some shells, such as GNU bash, allow the caret to be used as an extension.
- The extglob extensions are not standard. They are only available in Korn shell (enabled by default) and GNU bash (enabled via
shopt -s extglob).
Use in Tools
editTools and languages that utilize this regular expression syntax include:
- For the general glob syntax, all POSIX "bourne-compatible" shells.
- For the extglob part, Korn shell and bash.