batt.sh

#!/bin/sh
# Usage: ./batt.sh COMMAND
#
# Use the environment variables `critical' and `sleep_time' to refine this
# script.
# 
# Example: critical=50 ./batt.sh COMMAND
# Result: Every battery charge under 50% will result in COMMAND

if [ ! -d "/proc" ]
then
	echo "There is no /proc directory. Is this Linux? Exit." >&2
	exit 1
fi

if [ "`ls /proc/acpi/battery/`" = "" ]
then
	echo "No batteries found. Exit." >&2
	exit 1
fi

batteries=`echo /proc/acpi/battery/BAT* | sed 's/\s/\n/g' | awk '{print substr($argv, index($argv, "BAT"), length($argv))}' | sed 's/^BAT//'`
echo "Batteries: $batteries"

if [ "$sleep_time" = "" ]
then
	sleep_time=60
fi

if [ "$critical" = "" ]
then
	critical=10 
fi

present_batteries=""
for battery in $batteries
do
	if [ "`cat /proc/acpi/battery/BAT$battery/info | grep '^present:' | awk '{print $2}'`" = "yes" ]
	then
		if [ "$present_batteries" = "" ]
		then
			present_batteries="$battery"
		else
			present_batteries="$present_batteries $battery"
		fi
	fi
done

if [ "$present_batteries" = "" ]
then
	echo "No present batteries found. Exit." >&2
	exit 1
fi

echo "Present batteries: $present_batteries"

full_capacity=0

for battery in $present_batteries
do
	full_capacity=`expr \`grep '^last full capacity:' /proc/acpi/battery/BAT$battery/info | awk '{print $4}'\` + $full_capacity`
done

if [ $full_capacity -eq 0 ]
then
	echo "Hey. The sum of all full capacities is 0. There is a bug. Exit." >&2
	exit 2
fi

echo "Full capacity: $full_capacity mWh"

while :
do
	actual_charge=0
	actual_status=discharging
	for battery in $present_batteries
	do
		charging_state="`grep '^charging state:' /proc/acpi/battery/BAT$battery/state | awk '{print $3}'`"
		if [ "$charging_state" = "charging" -a "$actual_status" = "charged" ]
		then
			actual_status=charging
		elif [ "$actual_status" = "discharging" ]
		then
			actual_status=$charging_state
		fi
		
		actual_charge=`expr \`grep '^remaining capacity:' /proc/acpi/battery/BAT$battery/state | awk '{print $3}'\` + $actual_charge`
	done
	
	percent=`expr $actual_charge '*' 100 / $full_capacity`
	
	if [ $percent -le $critical -a "$actual_status" = "discharging" ]
	then
		echo -n "[critical]"
		cli=`echo $* | sed 's/__STATE__/'$actual_charge' mWh ('$percent' %)/g'`
		$cli &
	fi
	
	echo "[$actual_status] $actual_charge mWh ($percent %)"
	
	sleep $sleep_time
done