If the processes have varying runtimes you might consider not waiting until all of the current 5-process-group are finished but start a new one as soon as one of the running processes have finished.

The following pseudocode should be easy to implement. FANOUT is the number of processes you want to run in parallel, TIMEOUT should be set to some sensible number of seconds:

Code:

list-of-processes
while end-of-list is not reached do
     if <nr-of-started-procs> is smaller than FANOUT
          start next_process in background
          if <get next process from list> not empty
               next_process = next list entry
          else
               exit loop
          endif
     else
          wait TIMEOUT
     endif
enddo

wait for remaining processes to finish

You might want to put your processes to start in a shell array first, so you can easily check if you have reached the last element (=end of list).

I hope this helps.

bakunin