brightnessctl

This program allows you read and control device brightness on Linux. Devices, by default, include backlight and LEDs (searched for in corresponding classes). If omitted, the first found device is selected.

It can also preserve current brightness before applying the operation (allowing for usecases like disabling backlight on lid close).

Installation

The program is available in:

• Alpine Linux
• Arch Linux
• Void Linux
• Debian - starting with Buster (and derivatives)
• Ubuntu - starting with 18.04 (and derivatives)
• openSUSE - available in Tumbleweed, use OBS utilities/brightnessctl devel project for Leap < 15.1
• Fedora - available in Fedora 31+
• NixOS/nix - starting with 17.09, please see the NixOS Wiki page for the "best-practice" configuration file based installation

One can build and install the program using ./configure && make install. Consult ./configure --help for relevant build-time options.

Permissions

Modifying brightness requires write permissions for device files or systemd support. brightnessctl accomplishes this (without using sudo/su/etc.) by either of the following means:

1) installing relevant udev rules to add permissions to backlight class devices for users in video and leds for users in input. (done by default)

2) installing brightnessctl as a suid binary.

3) using the systemd-logind API.

FAQ

I'd like to configure the brightness of an external monitor

Use the ddcci-driver-linux kernel module to expose external monitor brightness controls to brightnessctl. Available in repositories of AUR, Debian, Nix, Ubuntu, Void.

Usage

Usage: brightnessctl [options] [operation] [value]

Options:
  -l, --list            list devices with available brightness controls.
  -q, --quiet           suppress output.
  -p, --pretend         do not perform write operations.
  -m, --machine-readable    produce machine-readable output.
  -n, --min-value       set minimum brightness, defaults to 1.
  -e, --exponent[=K]        changes percentage curve to exponential.
  -s, --save            save previous state in a temporary file.
  -r, --restore         restore previous saved state.
  -h, --help            print this help.
  -d, --device=DEVICE       specify device name (can be a wildcard).
  -c, --class=CLASS     specify device class.
  -V, --version         print version and exit.

Operations:
  i, info           get device info.
  g, get            get current brightness of the device.
  m, max            get maximum brightness of the device.
  s, set VALUE          set brightness of the device.

Valid values:
  specific value        Example: 500
  percentage value      Example: 50%
  specific delta        Example: 50- or +10
  percentage delta      Example: 50%- or +10%