Bash Patterns
External
Internal
Metacharacters
The following characters have a special meaning when a bash pattern is evaluated, and they need to be escaped to be matched literally:
*
* (star) matches any string, including the null string. When the globstar shell option is enabled, and ‘*’ is used in a filename expansion context, two adjacent ‘*’s used as a single pattern will match all files and zero or more directories and subdirectories. If followed by a ‘/’, two adjacent ‘*’s will match only directories and subdirectories.
?
? (question mark) matches a single character. The dot ('.') is not a metacharacter.
[...]
Matches any one of the enclosed characters.
For example:
[- :]
matches '-', space and ':'.
A pair of characters separated by a hyphen denotes a range expression; any character that falls between those two characters, inclusive, using the current locale’s collating sequence and character set, is matched. A digit is matches as follows:
[0-9]
If the first character following the ‘[’ is a ‘!’ or a ‘^’ then any character not enclosed is matched.
A ‘-’ may be matched by including it as the first or last character in the set.
A ‘]’ may be matched by including it as the first character in the set.
Classes
Within ‘[’ and ‘]’, character classes can be specified using the syntax [:class:], where class is one of the following classes defined in the POSIX standard:
- alnum
- alpha
- ascii
- blank
- cntrl
- digit
- graph
- lower
- punct
- space
- upper
- word: matches letters, digits, and the character ‘_’.
- xdigit
A character class matches any character belonging to that class.
/
To match a '/' (slash), use '\/'. If used in replacement constructs as variable expansion replacement, there is no need to escape slashes in the replacement string.
~
~ (tilda)
Non-Special Characters
These characters do not need to be escaped in bash patterns to match:
\ # forward slash . # dot - does NOT match any character, it just matches a dot
Paths
See / above.