Globstar: New Bash Globbing Option
In shell-speak, globbing is what the shell does when you use a wildcard in a command (e.g. * or ?). Globbing is matching the wildcard pattern and returning the file and directory names that match and then replacing the wildcard pattern in the command with the matched items. Bash version 4.0 adds a new globbing option called globstar which treats the pattern ** differently when it's set.
Normally, if you use the pattern ** on the command line it acts the same as the * pattern. For example, given the following directory:
$ ls -l total 8 -rw-r--r-- 1 mitch users 0 2010-05-05 10:36 a -rw-r--r-- 1 mitch users 0 2010-05-05 10:36 b drwxr-xr-x 2 mitch users 4096 2010-05-05 10:36 c drwxr-xr-x 2 mitch users 4096 2010-05-05 10:36 d
if you execute the following commands:
$ for i in ** > do > echo $i > done
you get the following output:
a b c d
If you now set the globstar option with the following command:
$ shopt -s globstar
and then re-run the for loop from above, you now get:
a b c c/e d d/f
With globstar set, bash recurses all the directories. Note that this will recurse all directory levels, not just one level.
You can see if globstar is set by issuing the shopt command without any arguments:
$ shopt ... force_fignore on globstar on gnu_errfmt off ...
or if you want to test it in a script you can use the -q option to shopt and test the exit status, for example:
if shopt -q globstar; then ... if
Mitch Frazier is an Associate Editor for Linux Journal.
|Reglue: Opening Up the World to Deserving Kids, One Linux Computer at a Time||Jul 29, 2014|
|diff -u: What's New in Kernel Development||Jul 23, 2014|
|Great Scott! It's Version 13!||Jul 21, 2014|
|Adminer—Better Than Awesome!||Jul 17, 2014|
|It Actually Is Rocket Science||Jul 16, 2014|
|Android Candy: Repix, Not Just Another Photo App||Jul 14, 2014|
- Reglue: Opening Up the World to Deserving Kids, One Linux Computer at a Time
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Numerical Python
- RSS Feeds
- NSA: Linux Journal is an "extremist forum" and its readers get flagged for extra surveillance
- diff -u: What's New in Kernel Development
- Tech Tip: Really Simple HTTP Server with Python
- Linux Systems Administrator
- Senior Perl Developer
- Great Scott! It's Version 13!