init() { if [ -e stack ]; then rm stack; fi } # force pop to blow up if empty
push() { echo $1 >> stack; }
pop() {
	tail -1 stack;
	x=`head -n -1 stack | wc -c`
	if [ $x -eq '0' ]; then rm stack; else
		truncate -s `head -n -1 stack | wc -c` stack
	fi
}
empty() { head -n -1 stack |wc -l; }
stack_top() { tail -1 stack; }