Watch a website and get emailed on changes

watch

#!/bin/bash
url="${1:?Usage: $0 url [recipient...]}"
shift
sha=$(curl -s $url | shasum);
while [[ $sha = $(curl -s $url | shasum) ]]; do
    sleep 15;
done
sendmail=$(type -p sendmail || { [[ -x /usr/sbin/sendmail ]] && echo /usr/sbin/sendmail || { echo "Can’t find sendmail!"; exit 1; }; });
$sendmail -F 'Website Watcher Bot' -f "bot+watcher@$HOSTNAME" "${@:-mail@$HOSTNAME}" << EOF
Subject: Website changed

Change on $url :)
EOF