pidcheck.sh

#!/bin/bash

self="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"

if [ -r "/tmp/${self}.pid" ]; then
  pid=`cat /tmp/${self}.pid`
	echo "Looks like the minifier is already running with pid=$pid!";
	echo "Checking to see if PID $pid is still running...";
	if [ -d "/proc/$pid" ]; then
		echo "Yup, it's really running according to /proc/$pid!" 
		exit 0;
	else
		echo "Doesn't look like it's running, replacing pid=$pid with pid=$$."
	fi
fi

echo $$ > /tmp/${self}.pid

# code goes here

rm /tmp/${0}.pid