Globbing

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Advanced Bash-Scripting Guide:
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19.2. Globbing
Bash itself cannot recognize Regular Expressions. In scripts, commands and utilities, such as sed and awk, interpret RE's.
Bash does carry out filename expansion, a process known as "globbing," but this does not use the standard RE set. Instead, globbing recognizes and expands wildcards. Globbing interprets the standard wildcard characters, * and ?, character lists in square brackets, and certain other special characters (such as ^ for negating the sense of a match). There are some important limitations on wildcard characters in globbing, however. Strings containing * will not match filenames that start with a dot, as, for example, .bashrc. [1] Likewise, the ? has a different meaning in globbing than as part of an RE.

bash$ ls -l total 2 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 a.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 b.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 c.1 -rw-rw-r-- 1 bozo bozo 466 Aug 6 17:48 t2.sh -rw-rw-r-- 1 bozo bozo 758 Jul 30 09:02 test1.txt bash$ ls -l t?.sh -rw-rw-r-- 1 bozo bozo 466 Aug 6 17:48 t2.sh bash$ ls -l [ab]* -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 a.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 b.1 bash$ ls -l [a-c]* -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 a.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 b.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 c.1 bash$ ls -l [^ab]* -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 c.1 -rw-rw-r-- 1 bozo bozo 466 Aug 6 17:48 t2.sh -rw-rw-r-- 1 bozo bozo 758 Jul 30 09:02 test1.txt bash$ ls -l {b*,c*,*est*} -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 b.1 -rw-rw-r-- 1 bozo bozo 0 Aug 6 18:42 c.1 -rw-rw-r-- 1 bozo bozo 758 Jul 30 09:02 test1.txt

Bash performs filename expansion on unquoted command-line arguments. The echo command demonstrates this.

bash$ echo * a.1 b.1 c.1 t2.sh test1.txt bash$ echo t* t2.sh test1.txt

Note
It is possible to modify the way Bash interprets special characters in globbing. A set -f command disables globbing, and the nocaseglob and nullglob options to shopt change globbing behavior.
See also Example 10-4.
Notes
[1]
Filename expansion can match dotfiles, but only if the pattern explicitly includes the dot.
~/[.]bashrc # Will not expand to ~/.bashrc ~/?bashrc # Neither will this. # Wild cards and metacharacters will not expand to a dot in globbing. ~/.[b]ashrc # Will expand to ~./bashrc ~/.ba?hrc # Likewise. ~/.bashr* # Likewise. # Setting the "dotglob" option turns this off. # Thanks, S.C.

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