[anthonyhn]

GNU Parallel is pretty useful. You can use it to run command line programs in parallel. For example, if you wanted to gzip compress all individual files in a directory and limit the number of jobs equal to the number of CPU cores on your machine:

ls | parallel --dry-run --jobs `nproc` 'gzip {}'

(Note you have to remove the --dry-run switch to actually run this, --dry-run only prints out the commands parallel will run, not actually execute them)

[qhwudbebd]

Sometimes xargs -P is useful too, but it's much more limited than GNU parallel.

[hayst4ck]

I think `xargs -P -I` is probably the closest thing to magic when it comes to commands.