Sample of parallel processing in Zsh script.

parallel_queue.zsh

#!/usr/bin/zsh

worker() {
  worker_num=$1
  while true
  do
    exec 9>| lock
    flock -x 9
    num=$(read -e)
    exec 9>&-

    if [[ -n $num ]]
    then
      print "Worker $worker_num : Hello, count=${num}"
    else
      print "Worker $worker_num ended."
      break
    fi
  done
}

print -l {1..1000} | (
  ( worker 1 ) &
  ( worker 2 ) &
  ( worker 3 ) &
  wait
  rm lock
)