Brightness auto adjustment

If your machine is equipped with a light sensor, you can set it up to auto adjust to the ambient light level. I found this feature to be good but not very well suited to my need. Sometimes an auto adjustment was made when I did not want it and sometimes it was not made at the exact time I needed it.
This is the reason why I came up with a script.

╭── Prepare your system

The only thing you will have to do once before using the script is to install the iio-sensor-proxy package and then run monitor-sensor to check that your light sensor is supported and automatically create the appropriate directories and files to control it.

Once done, you can freely remove the iio-sensor-proxy

╭── Variables you can adjust in the script

When called (with a keybinding/mouse binding), the script increases/decreases the screen backlight level by 5% step to match the light sensor level or your defined minimum in case the sensor level is below that.
I left comments in the script so it should be pretty much self explanatory.

The script uses several variables and the ones below can/should be adjusted:

• “minb” to define a minumum backlight level (currently set to 7%)
• “backlight”: check the path in your system and adapt if necessary
• “sensor”: check the path in your system and adapt if necessary

╭── Dependencies you can change

Everyone has his/her own preference. I use dunstify as my notification daemon and xbacklight to control the screen backlight. You can replace both and adjust the commands in the script.

╭── Stop talking, give me the script!

Here it is:

#!/usr/bin/env bash

# define variables
maxl=$(cat /sys/class/backlight/intel_backlight/max_brightness)
max=$(("$maxl"/100))
sensitivity=$((max/20))
minb=7 # set minimum backlight to 7%
minl=$((("$minb"/100)*96000))
backlight=$(cat /sys/class/backlight/intel_backlight/brightness)
sensor=$(cat /sys/bus/iio/devices/iio:device0/in_illuminance_raw)

if [ "$sensor" -gt "$max" ]; then
	target=$max
elif [ "$sensor" -lt 1 ]; then
	target="$min"
else
	target="$sensor"
fi

# increase screen brightness
if [ "$backlight" -lt "$sensor" ] && [ $(("$backlight" - "$sensor")) -lt "$sensitivity" ] && [ "$backlight" -lt "$maxl" ]
then
	target=$(("$target"/"$max"))
	itarget=$(("$backlight"/"$max"))
	until [ $itarget -ge "$target" ]; do
		itarget=$(("$itarget"+5))
		xbacklight -set "$itarget"
		sleep 0.05
	done
	dunstify -u low -t 1500 \"backlight: "$itarget"\"
	sleep 2 &&
		dunstify -C 0
fi

# decrease screen brightness
if [ "$backlight" -gt "$sensor" ] && [ $(("$backlight" - "$sensor")) -gt "$sensitivity" ] && [ "$backlight" -gt "$minl" ]; then
	target=$(("$target"/"$max"))
	itarget=$(("$backlight"/"$max"))
	until [ "$itarget" -le "$target" ] || [ "$itarget" -eq "$minb" ] ; do
		itarget=$(("$itarget"-5))
		if [ "$itarget" -le "$minb" ]; then
			xbacklight -set "$minb" # set screen brightness to minimum
			itarget="$minb"
		else
			xbacklight -set "$itarget"
		fi
		sleep 0.05
	done
	dunstify -u low -t 1500 \"backlight: "$itarget"\"
fi