Set Backlight in i3 - Arch Linux

Ashpex included in category Linux

2019-12-16 2024-06-22 564 words 3 minutes cc-by-nc-sa-4.0

Contents

Note

This article was last updated on 2024-06-22, the content may be out of date.

1 Why?

I once had struggle trying to get my backlight work in my Arch system with i3wm. So I thought I would share.

2 Keyboard backlight

Basic usage is as simple as

text

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

i3 config:

text

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

The scripts is available in the end of this post. 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.

Most Linux distributions encourage a practice in which each user has a specific directory for the programs he/she personally uses. This directory is called bin and is a subdirectory of your home directory. If you do not already have one, create it with the following command:

bash

[me@linuxbox me]$ mkdir bin

Move your script into your new bin directory:

bash

~/bin/kbdbacklight

Add directories to your path with the following command, where directory is the name of the directory you want to add:

bash

[me@linuxbox me]$ export PATH=$PATH:directory

In this case, it is:

bash

[me@linuxbox me]$ export PATH=$PATH:~/bin

Now, you are all set.

And here is the backlight script (click to expand):

bash

#!/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