Which command should I execute to change the brightness?

Question

My laptop's keyboard is half functional (literally, like half of the keys don't work), so I'm forced to use an external keyboard. However, since it doesn't have an Fn key (obviously), I want to create a custom keyboard shortcut to change the brightness up and down.

So, what command should I execute to change the brightness up or down? I want to create a custom keyboard shortcut for these commands.

Edit: I should point out that I took a look at the default keyboard shortcuts and found nothing to help me out.

Answer 1

The simple way to adjust brightness from terminal is using xrandr.

xrandr is used to set the size, orientation and/or reflection of the outputs for a screen. It can also set the screen size.

For more information about xrandr open terminal and run man xrandr.

First you need to find your display name,for that run the command in terminal:

xrandr -q | grep " connected"

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For Example:

ravan@ravan:~$ xrandr -q | grep " connected"
VGA1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 410mm x 230mm

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Here,In my system VGA1 is display name. Replace VGA1 with your system display.

Now run:

 xrandr --output VGA1 --brightness 0.7

Here range from 0.0 to 1.0 .

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Option 2:

To adjust screen brightness you can use xbacklight

Open terminal and run:

sudo apt-get install xbacklight

Usage:

usage: xbacklight [options]
where options are:
       -display <display> or -d <display>
       -help
       -set <percentage> or = <percentage>
       -inc <percentage> or + <percentage>
       -dec <percentage> or - <percentage>
       -get
       -time <fade time in milliseconds>
       -steps <number of steps in fade>

For example: xbacklight -inc 20 will increase by 20 percent.

Answer 2

You can use xdotool

sudo apt-get install xdotool

then control the brightness by executing

xdotool key XF86MonBrightnessDown

for decreasing and

xdotool key XF86MonBrightnessUp

for increasing. There are alternate options to change screen brightness but mostly they need root privileges and if you are trying to have key bindings, entering your password each time on an intermediate pop-up screen can be a bummer. You create custom keyboard shortcuts for these in systems setting (System Settings -> Keyboard -> Shortcuts -> Custom)

by pressing the + button at the bottom and inserting your command and its corresponding keyboard shortcut. You should log out and log back in for the effect to take place.