#!/bin/sh

battery_state=/proc/acpi/battery/BAT0/state
if ! grep -Fq "discharging" $battery_state; then
    echo "You must run this when not connected to AC" >&2
    exit 1
fi

tmA=0
num=10
delay=10
echo "Calculating average current draw over $(($num*$delay))s" >&2
for i in $(seq $num); do
    mA=$(sed -n 's/present rate: *\([0-9]*\) mA/\1/p' < $battery_state)
    echo $mA
    tmA=$(($tmA + $mA))
    sleep 10
done
echo "Average current consumption is $(($tmA/$num))mA" >&2