Bash Script for Running Parallel Queue

parallel_queue.sh

#!/bin/bash

# initialize a semaphore with a given number of tokens
open_sem(){
    mkfifo pipe-$$
    exec 3<>pipe-$$
    rm pipe-$$
    local i=$1
    for((;i>0;i--)); do
        printf %s 000 >&3
    done
}

# run the given command asynchronously and pop/push tokens
run_with_lock(){
    local x
    # this read waits until there is something to read
    read -u 3 -n 3 x && ((0==x)) || exit $x
    (
     ( "$@"; )
    # push the return code of the command to the semaphore
    printf '%.3d' $? >&3
    )&
}

# Define the maximum of parallel process in the queue
N=4
open_sem $N 

for i in {0..100}
do
    run_with_lock [WRITE_YOUR_PROCESS_HERE]
done