Piotr Gabryjeluk

Thank you for this hint. Parallel is very nice (present in Ubuntu repositories, though not Debian's ones).

xargs (GNU version) supports parallellism, xjobs (from Solaris but portable) does a better job of isolating output.

Before you choose between GNU Parallel, xjobs, and xargs you may want to read about the differences.

http://www.gnu.org/software/parallel/man.html#differences_between_xargs_and_gnu_parallel

http://www.gnu.org/software/parallel/man.html#differences_between_xjobs_and_gnu_parallel

A new intro video shows more examples: http://www.youtube.com/watch?v=OpaiGYxkSuQ

Check it out, I just posted another take on the issue. I don't use polling:
http://johannes.jakeapp.com/blog/category/fun-with-linux/201104/parallel-task-execution-in-bash

After those helpful comments, my favorite method to run things in parallel now is xargs :-).