#!/bin/bash

if cat /proc/acpi/video/VGA/LCD/brightness  | grep "current: 4"

then
echo 8 > /proc/acpi/video/VGA/LCD/brightness
exit 0
fi

if cat /proc/acpi/video/VGA/LCD/brightness  | grep "current: 1"

then
echo 4 > /proc/acpi/video/VGA/LCD/brightness
exit 0
fi

if cat /proc/acpi/video/VGA/LCD/brightness  | grep "current: 8"

then
echo 1 > /proc/acpi/video/VGA/LCD/brightness
exit 0
fi

echo 1 > /proc/acpi/video/VGA/LCD/brightness