rlafuente / backlight-by-hand

Wrapper script to directly manipulate system backlight files

fn-backlight

This is a custom way to change the backlight on systems for which xbacklight can't find outputs because they don't live at /sys/class/backlight. Such systems have backlight controls at a subdir such as /sys/class/backlight/intel_backlight. This script provides a wrapper interface to those backlight controls.

This was written with the purpose of binding the backlight controls to media keys in systems which, by their choice of window manager, don't have automatic function key mapping, as is the case with Awesome and i3. For these cases, this script can be mapped with xbindkeys to provide the same functionality -- see below.

Installation

Be sure to edit the script's variables (located at the beginning) to match your system's values, namely the location of the dir that contains the brightness and max_brightness files, as well as the step for raising/lowering and the minimum brightness value that you want.

This script needs to be run with sudo, since it directly edits the /sys/class/backlight/intel_backlight/brightness file. You'll want to add a line to your /etc/sudoers file so that you don't need to input the password every time:

username ALL = (root) NOPASSWD:/home/username/bin/fn-backlight

This example presumes you've placed the script inside ~/bin/.

Usage

# raise
fn-backlight up
# lower
fn-backlight down
# set to maximum level
fn-backlight max
# get the current value in percent
fn-backlight info
# toggle between minimum value and 50%
fn-backlight toggle

Mapping function keys with xbindkeys

This is an example config file for xbindkeys to map function keys appropriately:

"sudo ~/bin/fn-backlight up"
  XF86MonBrightnessUp
"sudo ~/bin/fn-backlight down"
  XF86MonBrightnessDown
"sudo ~/bin/fn-backlight toggle"
  m:0x8 + c:70

It was written for a Lenovo U31-70 laptop; run xbindkeys --key to find your own system's key codes and alter your config accordingly.