Shell Programming and Scripting

I have my Mac OS X program executing a shell script (a script that copies files to a drive). I want to make it so that the shell script automatically kills itself if it finds that the host .app is not running OR kill itself if the drive that it is copying files to has been unmounted. Right now what I have is the shell script polls using the UNIX "ps" command every time before it executes a command, and then kills itself if the app, and then also uses the "df" utility to check if the disk is mounted. like this:

Code:

#!/bin/sh

checkrunning()
{
	PS=$( /bin/ps -aex )
	if [[ $PS != */Contents/MacOS/MyAppBinary* ]]
		then
		exit 0
	fi
	DISKS=$( /bin/df | grep "$VOLPATH" )
	if [[ $DISKS != *"$1"* ]]
		then
		exit 0
	fi
}

checkrunning
cp /something /something/here/

checkrunning
cp /anothersomething /something/here/

However this polling wastes resources, so is there a better way to do this?

I'm using Mac OS X 10.6 using the default shell.