Execute list of commands in parallel with limit on the number of concurrent commands

parallel_exec.sh

#!/bin/bash -x

OLD_IFS="${IFS}"
IFS="
"
LIMIT=2

cmd_buff="`cat command_list.txt`"

declare -a cmd_list=($cmd_buff)

for line in "${cmd_list[@]}"; do
    echo ">> "$line
done

cmd_index=0

job_list=

while [ $cmd_index -lt ((${#cmd_list[@]}-1)) ]; do
    echo "Running command #"$((cmd_index+1))
    bash -xc "${cmd_list[$cmd_index]}; echo timeout ${cmd_list[$cmd_index]};" &
    cmd_index=$((cmd_index+1))

    running_count=`jobs | wc -l | awk '{print $1}'`
    while [ $running_count -ge $LIMIT -a ]; do
        running_count=`jobs | wc -l | awk '{print $1}'`
        echo "running_count=$running_count,LIMIT=$LIMIT"
        sleep 1
    done
done

wait