flipdot Shutdown on disconnected power supply

fd-power-watch.sh

#!/bin/bash
# When the power supply is disconnected, shut down machine after a defined time
# and warning messages

# Time in seconds to shutdown device after disconnected power supply
grace_time=500
timeout=0

while :; do
    state=$(upower -i "$battery" | grep state | awk '{print $2}')
    if [[ $(cat /sys/class/power_supply/AC/online) -lt 1 ]]; then
        time_left=$((grace_time-timer*60))
        notify-send -u critical "Power supply disconnected" "System will shutdown in $((time_left/60)) minutes"
        if [[ "$time_left" -le 0 ]]; then
            notify-send -u critical "SHUTTING DOWN SYSTEM"
            systemctl poweroff
            exit 0
        fi
        ((timer++))
    else
        timer=0
    fi
    sleep 60
done