How to run the bash script in parallel rather than sequentially?

Question

#!/bin/bash

some_array=($1)

echo "-- Setting-Up VM --"

for i in ${some_array[@]}; do
    echo "VM #: $i"

    case "$i" in

        "1")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;

        "2")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;

        "3")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;
        *)
        echo "unknown VM!"
        ;;
    esac
done

Can someone please guide me I have the above script which is executed when we run the script for instance ./vmSetup.sh "1 2 3" but this is executed sequentially. I had created this script but now I want to run the cases in the script i.e. 1, 2 and 3 in parallel. Can someone also tell me how to run for instance 8 cases in parallel?

Answer 1

Put each case ... esac statement in the background by ending it with &. Then use wait after the loop to wait for all the background processes to finish.

#!/bin/bash

some_array=($1)

echo "-- Setting-Up VM --"

for i in ${some_array[@]}; do
    echo "VM #: $i"

    case "$i" in

        "1")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;

        "2")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;

        "3")
        echo "Setting-Up VM $i"
        sshpass -p "root12"  ssh -tt -o StrictHostKeyChecking=no root@10.xx.x.xx <<EOF
        pwd
        nohup yes | /etc/rc.d/init.d/lifconfig
        su tarts
        nohup yes | vncserver
        sleep 10
        exit
        exit
EOF
        ;;
        *)
        echo "unknown VM!"
        ;;
    esac &
done

wait