backlight

Backlight

Application that sets the backlight brightness on Linux machines.

Usage

The application uses the commands (brightness, actual_brightness, max_brightness) under /sys/class/backlight/<device>. The device part is specific to the video card in the host machine. The app tries to determine the name automatically but it can also be explicitly given using the -cmd flag.

The application expects a percentage with which it should increase or decrease the brightness (accepted range: [-100 : 100]). It also prints the current and maximum values. If no percentage is given it only prints the values.

backlight [-cmd=<brightness commands directory>] [-p=<percentage>]

Installation

The application can be installed with the following command:

go install github.com/nagygr/backlight/cmd/backlight@latest

Please note, that this requires Go to be available on the system. It can be installed using the package manager of the host OS, e.g.:

pacman -S go            # Arch Linux, Manjaro, etc.
dnf install golang      # Fedora, Red Hat, etc.
apt-get install golang  # Debian, Ubuntu, etc.

Configuring access rights

Please note that, by default, the brightness file, which controls the backlight brightness, can only be written by root. In order to make it editable by an ordinary user, please create/edit the following file: /etc/udev/rules.d/backlight.rules:

ACTION=="add", SUBSYSTEM=="backlight", RUN+="/bin/chgrp video $sys$devpath/brightness", RUN+="/bin/chmod g+w $sys$devpath/brightness"

This line allows the participants of the video group to set the backlight brightness. Next, please add the user you wish to grant these rights to, to the video group:

sudo usermode -aG video <user name>