#!/bin/sh
BAT='/sys/class/power_supply/BAT1'
STATUS_DISCH='Discharging'
LOW='15'
while [ 0 ]; do
    bat_status=`cat ${BAT}/status`
    if [[ ${bat_status} == ${STATUS_DISCH} ]]; then
        bat_current=`cat ${BAT}/charge_now`
        bat_full=`cat ${BAT}/charge_full`
        bat_perc=`echo "${bat_current} / ${bat_full} * 100" | bc -l | head -c 6 | tr '.' ','`
        if [[ ${bat_perc} < ${LOW} ]]; then
            bat_perc_format=`printf '%.4lg\n' ${bat_perc}`
            notify-send "Battery low: ${bat_perc_format}%"
        fi
        sleep 120
    fi
done