parallel(1) - run programs in parallel
-j maxjobs
       Use to limit the number of jobs that are run at the same time.
-l maxload
       Wait as needed to avoid starting new jobs  when  the  system's  load  average  is  not  below  the
       specified limit.
-i     Normally  the command is passed the argument at the end of its command line. With this option, any
       instances of "{}" in the command are replaced with the argument.
-n     Number of arguments to pass to a command at a time. Default is 1.  Incompatible with -i