Executes command after a process completes

runafter

#!/bin/bash
if [ $1 == '--help' ] || [ $1 == 'help' ] || [ $1 == '-h' ] ; then
    echo "usage: runafter <pid> [-f] <command>"
    exit 0
fi

re='^[0-9]+$'
if ! [[ $1 =~ $re ]] ; then
   echo "error: first arg must be a pid of a running process" >&2
   exit 1
fi

pid=$1

start=2
if [ $2 == '-f' ] ; then
    start=3
fi

if ! [ -n "$pid" -a -e /proc/$pid ]; then
    if [ $2 != '-f' ]; then
        echo "error: process $pid is not running"
        echo "add -f after pid to force run even when a process is stopped"
        exit 1
    fi
fi

echo "Waiting for process $pid to finish..."
tail --pid=$pid -f /dev/null
printf "Process $pid finished, running command:\n\t${@:$start}"
"${@:$start}"