#!/bin/bash

function loop-until-up() {
	until nmap -sn $1 | grep "Host is up" > /dev/null ; do
		sleep 5s
	done
}

function alarm-while-up() {
	while nmap -sn $1 | grep "Host is up" > /dev/null ; do
		printf '\7'
		sleep 2s
	done
}

function main() {
	echo Waiting for $1...
	loop-until-up $1

	echo -n $1 went UP at
	date +" %H:%M, %a, %m/%d/%g"

	alarm-while-up $1

	echo -n $1 went back down at
	date +" %H:%M, %a, %m/%d/%g"
	main $1
}

if [ -z $1 ] ; then
	echo Missing IP address
else
	main $1
fi