Shell script for running commands in parallel

parallel.sh

#!/bin/sh
#
# Quick-and-dirty parallelizer, by Nicholas Clark
#
# Uses shell job-control to launch each argument as a subprocess.
# Waits until all subprocesses have finished. If all subprocesses
# returned 0, the result of the script is 0. Otherwise, the result
# will be the error-code of the first failed command in the argument
# list.
#
# All jobs are started at more-or-less the same time, so the number
# of subprocesses should probably be kept below 20 or so.

PIDS=""
RESULT=0

for _ in $(seq $#); do
    eval "$1" &
    PIDS="$PIDS $!"
    shift
done

for pid in $PIDS; do
    wait "$pid"
    _result=$?
    if [ "$_result" != "0" ]; then
        RESULT="$_result"
        break
    fi  
done

wait
exit $RESULT