#!/bin/sh
TRG=/tmp/shutdown.screensaver
date -d "+1 hour" +"%s" > "$TRG"
while true; do
    now=$(date +"%s")
    [ -f "$TRG" ] || break
    trg=$(cat "$TRG")
    if [ "$now" -ge "$trg" ]; then
        shutdown -h now
	rm "$TRG"
    fi
    sleep 5
done