Get all child PIDs recursively

all_child_pids.sh

#!/bin/bash

ppids=$1

if [ "x$ppids" == "x" ]
then
    echo "Usage: $0 PPID"
    exit 1
fi

function getChildPids() {
    ppid=$1
    echo `ps --no-headers -o pid --ppid $ppid`
}

level=1
pids=""

while [ "x$ppids" != "x" ]
do
    next_ppids=""
    for ppid in $ppids
    do
        i=0
        while [ $i -lt $level ]
        do
            echo -n ">" >&2
            i=$((i+1))
        done
        echo " $ppid" >&2
        pids="$pids,$ppid"
        childs=`getChildPids $ppid`
        next_ppids="$childs $next_ppids"
    done
    level=$((level+1))
    ppids=$next_ppids
done

echo "ALL PIDS: $pids" >&2
echo ${pids:1}