batt.sh

#!/bin/sh

f1='/proc/acpi/battery/BAT1/alarm'
f2='/proc/acpi/battery/BAT1/state'

s1=$(awk '/alarm/ { print $2 ; exit}' < "$f1")
s2=$(awk '/remaining capacity/ { print $3 ; exit}' < "$f2")

if [[ $s2 -le $s1 ]]; then
/sbin/shutdown -h +2 "Falta de bateria: $s2 mWh"
fi