battery-status-led/battery_status_led.sh

#!/bin/bash

# Copyright 2018 Denes Matetelki

# This file is part of battery_status_led.

# battery_status_led is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License v3 as published by the Free
# Software Foundation.

# battery_status_led is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License v3 for
# more details.

# You should have received a copy of the GNU General Public License v3 along
# with battery_status_led. If not, see
# https://www.gnu.org/licenses/gpl-3.0.html.

# limits in percentages
LOW=10 # flip LED every 2s
CRIT=5 # flip led every 0.5s

BAT_FULL_DEV=/sys/class/power_supply/BAT0/energy_full_design
BAT_STATUS_DEV=/sys/class/power_supply/BAT0/status
BAT_NOW_DEV=/sys/class/power_supply/BAT0/energy_now
CAPSLOCK_LED_DEV=/sys/class/leds/input4\:\:capslock/brightness

# If not set by the systemd service file
LED_DEV=${BATTERY_STATUS_LED_DEV:-$CAPSLOCK_LED_DEV}

LED=0
while :
do
	# If charging, sleep 1m, then restart the cycle
	STATUS=cat $BAT_STATUS_DEV
	if [ $STATUS == "Charging" ] ; then
		echo 0 > $LED_DEV
		sleep 1m
		continue
	fi

	BAT_NOW=cat $BAT_NOW_DEV
	BAT_PCT=$(($BAT_NOW * 100 / $BAT_FULL))

	# If battery has more than >10% left, sleep 1m then restart the cycle
	if (($BAT_PCT >= $LOW )) ; then
		sleep 1m
		continue
	fi

	# If battery is on low, but not crytical, flip LED every 2s
	if (( $BAT_PCT < $LOW )) && (( $BAT_PCT >= $CRIT)) ; then
		LED=$((1 ^ $LED))
		echo $LED > $LED_DEV
		sleep 2s
		continue
	fi

	# If battery is on crytical flip capslock LED every 0.5s
	if (( $BAT_PCT < $CRIT )) ; then
		LED=$((1 ^ $LED))
		echo $LED > $LED_DEV
		sleep 0.5s
		continue
	fi
done