Control screen brightness using xrandr

brightness.md

#!/bin/bash
# brightness: Change all monitors brightness in software.
# by hackerb9, 2019,2021

# Examples:  brightness 75;  brightness -10; brightness +10
# Usage:
#	brightess [n] [+n] [-n]
#	n	An integer from 0 to 100 specifies a brightness level.
#	+n	Increase brightness by n.
#	-n	Decrease brightness by n.
#		No argument shows current brightness level.

b=$(xrandr --current --verbose | grep Brightness)
b=${b##*: }			# Remove "Brightness: "
b=${b#0.}			# 0.30 --> 30
[[ $b == "1.0" ]] && b="100"
case $1 in
    +*|-*)
	b=$((b $1))		# b=b+10,  b=b-10
	;;
    [0-9]*)
	b=$1			# b=75
	;;
    *)
	echo $b; exit
	;;
esac

[[ $b -lt 0 ]] && b=0
[[ $b -gt 100 ]] && b=100

if [[ $b -eq 100 ]]; then
    b=1.0
else
    b=0.$b
fi

outputs=$(xrandr --current | awk '$2 == "connected" {print $1}')
for o in $outputs; do
    xrandr --output $o --brightness $b
done	

1. Save script as brightness
2. chmod 755 brightness to make the file executable
3. sudo mv brightness /usr/local/bin to make it globally executable
4. Set shortcuts in Gnome

• brightness -10
• brightness +10

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credit: https://askubuntu.com/questions/899821/control-monitor-brightness-with-keyboard-shortcut#answer-1173970