Just a quick one:
xargs can help you to start multiple processes simultaneously:
$ time echo $'1\n2' | xargs -n 1 sleep
real 0m3.007s
user 0m0.001s
sys 0m0.007s
$ time echo $'1\n2' | xargs -P 2 -n 1 sleep
real 0m2.007s
user 0m0.001s
sys 0m0.006s
With -P N
or --max-procs=N
xargs will start up to N
processes at the
same time.