#!/bin/bash

# make sure we can find wget
if ! which wget 2> /dev/null 1> /dev/null; then
	echo "Can't find wget in PATH"
	exit 1
fi

# make sure we have acceptable args
if [[ $# -lt 2 ]] || echo $2 | grep -E '[^0-9]+' > /dev/null; then
	echo $0: watch a webpage for changes
	echo usage: $0 "<URI> <interval (seconds)>"
	exit 1
fi

# get the md5sum of the page
new=$(wget -qO- "$1" | md5sum)
changes=0

# refresh the page at the specified interval, and compare the md5sum
while [ true ]; do
	old=$new
	new=$(wget -qO- "$1" | md5sum)

	[[ "$old" != "$new" ]] && ((changes++))

	echo "$(date '+[%l:%M:%S %p]') CHANGES: $changes"
	sleep $2
done