How can I run a list of commands in parallel?

Use GNU parallel. It's an incredibly powerful tool and official packages exist for about 20 or so linux distros. What's that? You have an excuse as to why you can't use it? Here's a simple example showing how to run a list or file of commands in parallel:

Contents of jobs.txt:

sleep 1; echo "a"sleep 3; echo "b"sleep 2; echo "c"

Command:

time parallel :::: jobs.txt

Results:

acbreal    0m3.332suser    0m0.170ssys     0m0.037s

Notes:

If you wish to keep the order the same as the input, pass the -k flag to GNU parallel.

If you have more than eight cores and only wish to process with eight cores, add -j 8 to the args list.

The man page is a good read, but if you haven't already read this tutorial I would highly recommend the time investment.

You can use xargs to read in the file, while limiting the maximum number of processes to the number of available cores. For example:

cores=$(fgrep -c processor /proc/cpuinfo)xargs --arg-file=/tmp/foo \      --max-procs=$cores  \      --replace \      --verbose \      /bin/sh -c "{}"

You can start new processes on the background simply by running a command with &. There is an example here describing a solution of your problem.