check_battery(){
    if [[ -z "$BATTERY_DEV" || $LAST_BATTERY_CHECK -gt 5 ]] ; then
        LAST_BATTERY_CHECK=0
        BATTERY_DEV="AC"
        for device in `ls /sys/class/power_supply`
        do
            if [[ "`cat /sys/class/power_supply/$device/type`" = "Battery" ]] ; then
                BATTERY_DEV=$device
                break
            fi
        done
    fi
    ((LAST_BATTERY_CHECK++))
    BATTERY_STATE="AC"
    if [[ "$BATTERY_DEV" = "AC" ]] ; then
        return
    elif [[ ! -e "/sys/class/power_supply/$BATTERY_DEV" ]] ; then
        BATTERY_DEV=""
        return
    fi
    FULL=`cat /sys/class/power_supply/$BATTERY_DEV/charge_full`
    PRESENT=`cat /sys/class/power_supply/$BATTERY_DEV/present`
    CHARGE=`cat /sys/class/power_supply/$BATTERY_DEV/charge_now`
    STATUS=`cat /sys/class/power_supply/$BATTERY_DEV/status`
    if [ "$PRESENT" != "0" ] ; then
        CHARGE=$(($CHARGE*100/$FULL))
      case $STATUS in
        Full)
          SIGN="f";;
        Charging)
          SIGN="c";;
        Discharging)
          SIGN="d";;
        *)
          SIGN="u";;
      esac
      BATTERY_STATE="$CHARGE% [$SIGN]"
    fi
}