#!/bin/bash

#This script outlines a very basic service system that only allows one version to be run at a time.

#Base location of lock file.
loc=`dirname $0`


#Function to run when this script exits.
function rmlock {
    if [[ "$remove" -eq 1 ]]; then
        kill `cat "$loc/.lock"`
        rm "$loc/.lock";
    fi
}
#Trap exit signals.
trap rmlock EXIT


#Check if the lock file exists.
remove=1
if [[ -e "$loc/.lock" ]]; then
    echo "Nope. One is already running with PID:" `cat "$loc/.lock"`
    remove=0
else
    touch "$loc/.lock"
    #The script or program to run.
    echo "Do thing" &
    echo $! >> "$loc/.lock"
    wait
fi