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For my i3 window-manager settings, I am looking for a command line tool, similar to xbacklight, but to control the brightness of the leds which are in the keyboard.

Basically, I can set up the leds through a command line, but it requires to be root:

# Light off the leds echo 0 > /sys/class/leds/smc::kbd_backlight/brightness # Light on the leds (full power) echo 100 > /sys/class/leds/smc::kbd_backlight/brightness

I know that it is possible because Gnome3 has support for that, but I do not know exactly how they proceed...

For now, my ~/.config/i3/config looks like this:

# screen brightness controls bindsym XF86MonBrightnessUp exec xbacklight -inc 10 bindsym XF86MonBrightnessDown exec xbacklight -dec 10 # keyboard backlight controls #TODO # XF86KbdBrightnessUp # XF86KbdBrightnessDown

So, is there a tool, similar to xbacklight to do the same than screen brightness with keyboard backlight? It would be even better if this tool would have the control on both (screen and keyboard).

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3 Answers 3

Reset to default
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Giorgos Keramidas wrote a script that relies in dbus and UPower - which most desktop distros have up and running.

I would recommend using this instead of scripts that write to /sys/class/... as they need to be run as root - either through sudo or a by having SUID set - and that is bad security practice.

Basic usage is as simple as

kbdbacklight up kbdbacklight down kbdbacklight [ 0 | 1 | 2 | 3 ]

Add this to the i3 config

# increase/decrease keyboard brightness bindsym XF86KbdBrightnessUp exec kbdbacklight up bindsym XF86KbdBrightnessDown exec kbdbacklight down

The script itself is very simple

#!/bin/sh # By Giorgos Keramidas # backlight_get # Print current keyboard brightness from UPower to stdout. backlight_get() { dbus-send --type=method_call --print-reply=literal --system \ --dest='org.freedesktop.UPower' \ '/org/freedesktop/UPower/KbdBacklight' \ 'org.freedesktop.UPower.KbdBacklight.GetBrightness' \ | awk '{print $2}' } # backlight_get_max # Print the maximum keyboard brightness from UPower to stdout. backlight_get_max() { dbus-send --type=method_call --print-reply=literal --system \ --dest='org.freedesktop.UPower' \ '/org/freedesktop/UPower/KbdBacklight' \ 'org.freedesktop.UPower.KbdBacklight.GetMaxBrightness' \ | awk '{print $2}' } # backlight_set NUMBER # Set the current backlight brighness to NUMBER, through UPower backlight_set() { value="$1" if test -z "${value}" ; then echo "Invalid backlight value ${value}" fi dbus-send --type=method_call --print-reply=literal --system \ --dest='org.freedesktop.UPower' \ '/org/freedesktop/UPower/KbdBacklight' \ 'org.freedesktop.UPower.KbdBacklight.SetBrightness' \ "int32:${value}}" } # backlight_change [ UP | DOWN | NUMBER ] # Change the current backlight value upwards or downwards, or # set it to a specific numeric value. backlight_change() { change="$1" if test -z "${change}" ; then echo "Invalid backlight change ${change}." \ "Should be 'up' or 'down'." >&2 return 1 fi case ${change} in [1234567890]|[[1234567890][[1234567890]) current=$( backlight_get ) max=$( backlight_get_max ) value=$( expr ${change} + 0 ) if test ${value} -lt 0 || test ${value} -gt ${max} ; then echo "Invalid backlight value ${value}." \ "Should be a number between 0 .. ${max}" >&2 return 1 else backlight_set "${value}" notify-send -t 800 "Keyboard brightness set to ${value}" fi ;; [uU][pP]) current=$( backlight_get ) max=$( backlight_get_max ) if test "${current}" -lt "${max}" ; then value=$(( ${current} + 1 )) backlight_set "${value}" notify-send -t 800 "Keyboard brightness set to ${value}" fi ;; [dD][oO][wW][nN]) current=$( backlight_get ) if test "${current}" -gt 0 ; then value=$(( ${current} - 1 )) backlight_set "${value}" notify-send -t 800 "Keyboard brightness set to ${value}" fi ;; *) echo "Invalid backlight change ${change}." >&2 echo "Should be 'up' or 'down' or a number between" \ "1 .. $( backlight_get_max )" >&2 return 1 ;; esac } if test $# -eq 0 ; then current_brightness=$( backlight_get ) notify-send -t 800 "Keyboard brightness is ${current_brightness}" else # Handle multiple backlight changes, e.g.: # backlight.sh up up down down up for change in "$@" ; do backlight_change "${change}" done fi

Just save somewhere in your PATH and enjoy. I went with the name kbdbacklight and used it in the examples and i3 config above, please be mindful to update those if you name it differently.

Please note that Giorgio's script also makes use of notify-send, so make sure you have the right package installed (libnotify-bin on Debian and Ubuntu) or comment/remove those lines from the script.

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Use light:

bindsym XF86KbdBrightnessUp exec light -k -A 10 bindsym XF86KbdBrightnessDown exec light -k -U 10

It is available in a packaged version for Arch and Fedora at the moment. But you can always build if from source easily. Find the git repository here: https://github.com/haikarainen/light .

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  • 1
    it can also replace xbacklight, which sometimes does not work on some distributions Commented Sep 2, 2018 at 18:33
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You could write your own pretty easily.

Create two shell scripts containing the echo lines above somewhere in your path (/usr/local is the normal place). Set the permissions 755 owned by root. Then either edit your sudoers file to allow them to be run as root, or use chmod +s to set them SUID.

This sort of thing is considered a security risk, BTW, so make absolutely sure the permissions are set appropriately. You don't want anyone without root permissions to be able to edit the scripts, and you don't want the scripts to use any input.

It would be trivial to add support for a brightness level flag, but unless you're an accomplished shell scripter I'd recommend against it as a bug in your code would be a security hole.

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  • Yes, I know. It should be quite easy. But, before trying to do it I was looking for something already done. Commented Feb 6, 2016 at 20:19
  • Give me a few minutes to figure out github and I'll have a C solution for you. Commented Feb 6, 2016 at 21:38
  • I've written a utility for it. I have minimal testing since I'm on a desktop without keyboard backlighting. Look at github.com/Spauldo/kbd_backlight Commented Feb 6, 2016 at 21:53
  • Actually, only using sudo will work. Setting the SUID bit on shell scripts (or any other kind of script) does not work. At least not in the manner that it allows the script to be run as other user. The reason is that the process that is actually run is /bin/sh or whatever may be set in the #!-line and not the script itself. You would have to set SUID on the shell binary (e.g. /bin/sh) and that most assuredly would be a massive security risk. Commented Feb 16, 2016 at 7:18
  • You're right, I discovered that myself a few days ago when writing a firewall control script on OpenBSD. The utility I linked to above should work, though. Commented Feb 16, 2016 at 15:15

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