Bash Tips: Wildcards

Annika Backstrom
in misc, on 16 March 2004. It is tagged and #Scripting.

Many text mode guerrillas use Bash on a daily basis, almost always with some form of "globbing" (aka. "pattern matching" or "wildcards"). From what I've seen, this is usually limited to the asterisk, as in ls -l adam*.jpg, or worse, just ls -l adam*. ("Worse" being synonymous with "less explicit" in this definition.)

The asterisk is a perfectly valid wildcard, but it's not the only one: the question mark is pretty useful as well. It will match a single character, as opposed to any number of characters:

annika@aziz:~$ ls
file-index.txt    file1.txt  file3.jpg  file4.txt  file6.jpg
file-summary.txt  file2.jpg  file3.txt  file5.jpg  file6.txt
file1.jpg         file2.txt  file4.jpg  file5.txt
annika@aziz:~$ ls file?.txt
file1.txt  file2.txt  file3.txt  file4.txt  file5.txt  file6.txt

Pretty nice, but we can get even more explicit. What if we only want the first three text files?

annika@aziz:~$ ls file[1-3].txt
file1.txt  file2.txt  file3.txt

Or the first three text files and their corresponding images?

annika@aziz:~$ ls file[1-3].{txt,jpg}
file1.jpg  file1.txt  file2.jpg  file2.txt  file3.jpg  file3.txt

The curly brace above will expand the touching glob into a new word. The glob a{1,2} becomes a1 a2. This is very hand for moving files with long, complicated names:

annika@aziz:~$ mv long_name_that_autocompleted_poorly{1,2}.txt

That would rename long_name_that_autocompleted_poorly1.txt to long_name_that_autocompleted_poorly2.txt. Note that you're not limited to just two values in the braces, and you can have a blank value.