17.2. Globbing

Bash itself cannot recognize Regular Expressions. Inside scripts, it is commands and utilities -- such as sed and awk -- that interpret RE's.

Bash does carry out filename expansion [1] -- a process known as globbing -- but this does not use the standard RE set. Instead, globbing recognizes and expands wild cards. Globbing interprets the standard wild card characters, * and ?, character lists in square brackets, and certain other special characters (such as ^ for negating the sense of a match). There are important limitations on wild card characters in globbing, however. Strings containing * will not match filenames that start with a dot, as, for example, .bashrc. [2] 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 means expanding filename patterns or templates containing special characters. For example, example.??? might expand to example.001 and/or example.txt.

[2]

Filename expansion can match dotfiles, but only if the pattern explicitly includes the dot as a literal character.
   1 ~/[.]bashrc    #  Will not expand to ~/.bashrc
   2 ~/?bashrc      #  Neither will this.
   3                #  Wild cards and metacharacters will NOT
   4                #+ expand to a dot in globbing.
   5 
   6 ~/.[b]ashrc    #  Will expand to ~/.bashrc
   7 ~/.ba?hrc      #  Likewise.
   8 ~/.bashr*      #  Likewise.
   9 
  10 # Setting the "dotglob" option turns this off.
  11 
  12 # Thanks, S.C.

    Place for this material granted by linux and technology portal www.net4me.ru