#!/bin/bash
#store current state on start
last_state=`cat /proc/acpi/battery/BAT1/state`
#lets write it to console
echo "current_state: $last_state"
#keep looking for changes using an infinite loop
while true
do
state=`cat /proc/acpi/battery/BAT1/state`
if [[ "$state" == "$last_state" ]];
then
echo "state not changed don't do anything"
else
echo "state changed to $state , do something now"
#update last state
last_state=`echo $state`
fi
#just wait a little to avoid high cpu load
sleep 5
done