Filename Expansion

Pattern Matching

How the shell matches patterns.

After word splitting, unless the -f option has been set (see The Set Builtin), Bash scans each word for the characters ‘*’, ‘?’, and ‘[’. If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of filenames matching the pattern (see Pattern Matching). If no matching filenames are found, and the shell option nullglob is disabled, the word is left unchanged. If the nullglob option is set, and no matches are found, the word is removed. If the failglob shell option is set, and no matches are found, an error message is printed and the command is not executed. If the shell option nocaseglob is enabled, the match is performed without regard to the case of alphabetic characters.

When a pattern is used for filename expansion, the character ‘.’ at the start of a filename or immediately following a slash must be matched explicitly, unless the shell option dotglob is set. The filenames ‘.’ and ‘..’ must always be matched explicitly, even if dotglob is set. In other cases, the ‘.’ character is not treated specially.

When matching a filename, the slash character must always be matched explicitly by a slash in the pattern, but in other matching contexts it can be matched by a special pattern character as described below (see Pattern Matching).

See the description of shopt in The Shopt Builtin, for a description of the nocaseglob, nullglob, failglob, and dotglob options.

The GLOBIGNORE shell variable may be used to restrict the set of file names matching a pattern. If GLOBIGNORE is set, each matching file name that also matches one of the patterns in GLOBIGNORE is removed from the list of matches. If the nocaseglob option is set, the matching against the patterns in GLOBIGNORE is performed without regard to case. The filenames . and .. are always ignored when GLOBIGNORE is set and not null. However, setting GLOBIGNORE to a non-null value has the effect of enabling the dotglob shell option, so all other filenames beginning with a ‘.’ will match. To get the old behavior of ignoring filenames beginning with a ‘.’, make ‘.*’ one of the patterns in GLOBIGNORE. The dotglob option is disabled when GLOBIGNORE is unset.