How to get child process from parent process

I've written a script to get all child process pids of a parent process. Here is the code. Hope it will help.

function getcpid() {
    cpids=`pgrep -P $1|xargs`
#    echo "cpids=$cpids"
    for cpid in $cpids;
    do
        echo "$cpid"
        getcpid $cpid
    done
}

getcpid $1

Just use :

pgrep -P $your_process1_pid

To get the child process and thread, pstree -p PID. It also show the hierarchical tree

I am not sure if I understand you correctly, does this help?

ps --ppid <pid of the parent>