Increase or decrease brightness of screen.

edit_brightness

#!/usr/bin/env bash
#
# Increase or decrease brightness of screen.
# 
# Example usage:
#
#   $ edit_brightness -50
#   $ edit_brightness 10
# 
# Make sure /sys/class/backlight/radeaon_b10/brightness is writable. This can
# be done add the folowing line to crontab file of root:
#
#   @reboot chmod o+w /sys/class/backlight/radeon_bl0/brightness
#
set -e

SYS_PATH="/sys/class/backlight/radeon_bl0"
CUR_BRIGHTNESS=$(cat "$SYS_PATH/actual_brightness")
NEW_BRIGHTNESS=$(($CUR_BRIGHTNESS + $1))

echo $NEW_BRIGHTNESS | tee "$SYS_PATH/brightness" &> /dev/null