Similar to acpilight, but written in C and requires user to specify an interface. Why C? Because I don't want programs holding back python system updates.
First, download the source using either HTTP or SSH:
$ git clone https://github.com/Kamiyaa/arclight.git
$ git clone git@github.com:Kamiyaa/arclight.git
Then install using meson:
$ meson build
$ ninja -C build/
# ninja -C build/ install
$ arclight # list all valid interfaces
intel_backlight
tpacpi::thinkvantage
tpacpi::standby
input2::capslock
input2::numlock
tpacpi::thinklight
phy0-led
tpacpi::power
input2::scrolllock
$ arclight -i intel_backlight -u 5 # increase brightness by 5%
$ arclight -i intel_backlight -d 5 # decrease brightness by 5%
$ arclight -i intel_backlight -s 255 # set brightness to 255 (vendor specific)