#!/bin/bash

###########################################################################
# Script for automatically shutting down an acpi-enabled laptop 
#
# This script should be run periodically from cron or the like, and
# can be modified to fit your needs. It checks the remaining battery
# life and compare it to a threshold of the total capacity, and shuts
# the computer down if the capacity is too low. This has been useful
# when I have left my laptop running but unplugged and forgot about
# it. This script should be run as root (for shutdown capability).
#
# I run this script every minute or so, so the crontab entry looks
# like this:
#    * * * * * /usr/local/sbin/auto_lowbatt_shutdown
#
# Copyright (c) 2003 greg hamerly (greg_hamerly at baylor dot edu)
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program 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 for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.  or see http://www.gnu.org/copyleft/gpl.html
#

AC="/proc/acpi/ac_adapter/ACAD/state"
BATT_STATE="/proc/acpi/battery/BAT1/state"
BATT_INFO="/proc/acpi/battery/BAT1/info"

# if the computer is plugged in, then just exit
if grep -q "on-line" $AC
then
    exit 0
fi

# find out how much power is left, what is the total capacity, and the
# threshold at which we will automatically shut down (2% of the
# capacity)
remain=`grep "remaining capacity:" $BATT_STATE | sed "s/[^0-9]//g"`;
capacity=`grep "design capacity:" $BATT_INFO | sed "s/[^0-9]//g"`;
let threshold="$capacity * 2 / 100"

if [[ $remain -lt $threshold ]]
then
    date=`date`;
    echo "shutting down due to low battery at $date"
    exec /sbin/shutdown -h now
fi