Bash script that throws a message when battery is low

remaining_battery.sh

#!/bin/bash
# Written by Pablo Olmos de Aguilera C. <pablo at glatelier dot org>

LIMIT=1000
MESSAGE='¡Queda poca batería! ¡Corre a buscar el cargador!'
BAT_DIR='/proc/acpi/battery/BAT0'

echo 'running...'
initial=$(cat ${BAT_DIR}/* | grep 'remaining' | awk '{ print $3 }')
#rate=$(cat /proc/acpi/battery/BAT0/* | grep 'rate' | awk '{ print $3 }')
#hours_left=$(( $initial / $rate ))
#echo "Ahora hay unos ${initial} mWh... a un supuesto gasto de ${rate} por hora,\
# por lo tanto -en teoría- debería haber batería para ${hours_left} horas"

if (cat ${BAT_DIR}/* | sed 's/ //g' | uniq | grep 'present:no' > /dev/null); then
  echo 'no battery present...exiting'
  exit 1
fi

while :; do
  remaining=$(cat ${BAT_DIR}/* | grep 'remaining' | awk '{ print $3 }')
  if (($remaining < $LIMIT)); then
    notify-send "${MESSAGE}"
    echo $remaining
    sleep 540
  fi
  sleep 60
done