uptime -sh

#!/bin/bash

upSeconds="$(cat /proc/uptime | grep -o '^[0-9]\+')"
upMins=$((${upSeconds} / 60))

if [ "${upMins}" -gt "5" ]
then
 zenity --warning --text "Your session time is about to expire! You have 300 sec. to save your work and logout."
 killall firefox // kill -9 -1 // reboot
#    echo "Up for ${upMins} minutes"
#else
#    echo "Up five minutes or less"
fi