Xbacklight
From wikinotes
Adjust the screen backlight from the commandline.
Documentation
man xbacklight
https://man.archlinux.org/man/extra/xorg-xbacklight/xbacklight.1.en
Install
pacman -S xorg-xbacklight
Usage
xbacklight -set 40
Adjust the screen backlight from the commandline.
man xbacklight
https://man.archlinux.org/man/extra/xorg-xbacklight/xbacklight.1.en
pacman -S xorg-xbacklight
xbacklight -set 40