Xargs: change working directory to file path before executing?

Solution 1:

There exist commands to extract a directory name (dirname) and file name (basename) from a path. So you could do something like

find . -name '*.rar' -print0 | \
xargs -0 -I{} -n1 -P4 /bin/sh -c 'cd "$(dirname {})"; unrar x "$(basename {})"'

AFAIK, xargs doesn't support changing directories, so you would need some intermediary to do that, hence the /bin/sh. You mentioned writing a wrapper around unrar, and that is basically what this is doing, except in one-liner form.

Solution 2:

Using GNU Parallel it looks like this:

find . -name '*.rar' | parallel cd {//} '&&' unrar x {/}

GNU Parallel is a general parallelizer and makes is easy to run jobs in parallel on the same machine or on multiple machines you have ssh access to.

If you have 32 different jobs you want to run on 4 CPUs, a straight forward way to parallelize is to run 8 jobs on each CPU:

GNU Parallel instead spawns a new process when one finishes - keeping the CPUs active and thus saving time:

Installation

If GNU Parallel is not packaged for your distribution, you can do a personal installation, which does not require root access. It can be done in 10 seconds by doing this:

(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash

For other installation options see http://git.savannah.gnu.org/cgit/parallel.git/tree/README

Learn more

See more examples: http://www.gnu.org/software/parallel/man.html

Watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Walk through the tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html

Sign up for the email list to get support: https://lists.gnu.org/mailman/listinfo/parallel