Automatic keyboard backlight on/off on Thinkpad bash script

akbl.sh

#!/bin/bash

startup_time="20:00"
end_time="08:00"
inactivity_time=10000
polling_interval=0.5
device=tpacpi::kbd_backlight
on_value=1
off_value=0

# Initial state
brightnessctl -d $device s $off_value

light_status=off
while true; do

	idle=`xprintidle`
	if [ "$light_status" == "off" ]; then
		if [ $idle -lt $inactivity_time ]; then
			current_time_epoch=$(date +%s)
			startup_time_epoch=$(date +%s -d "today $startup_time")
			end_time_epoch=$(date +%s -d "today $end_time")
			if [ $current_time_epoch -ge $startup_time_epoch ] || [ $current_time_epoch -le $end_time_epoch ]; then        
				brightnessctl -d $device s $on_value
				light_status=on
				echo "Lights on"
			else
				sleep 10
			fi
		fi
	fi

	if [ "$light_status" == "on" ]; then
		if [ $idle -gt $inactivity_time ]; then
			brightnessctl -d $device s $off_value
			light_status=off
			echo "Lights off"
		fi
	fi

	sleep $polling_interval

done