XPS 15 7590 - Backlight Script

xbacklightmon.sh

#!/bin/bash

#use LC_NUMERIC if you are using an European LC, else printf will not work because it expects an comma instead of a decimal point
LC_NUMERIC="en_US.UTF-8"

#Exit with 1 if $DISPLAY env isn't set. Helps when using the start up script below
[ -z "$DISPLAY" ] && exit 1;

# modify this path to the location of your backlight class
path=/sys/class/backlight/intel_backlight

read -r max < "$path"/max_brightness

luminance() {
	read -r level < "$path"/actual_brightness
    factor=$((max / 100))
    ret=`printf '%d\n' "$((level / factor))"`
    if [ $ret -gt 100 ]; then
       ret=100
    fi
    printf `echo "$ret / 100" | bc -l`
}

# support both intel and nvidia
DEVICE=eDP-1
if [ ! -z "$(xrandr -q --output $DEVICE 2>&1)" ]; then
  DEVICE=eDP-1-1
fi

xrandr --output $DEVICE --brightness "$(luminance)"

inotifywait -me modify --format '' "$path"/actual_brightness | while read; do
    xrandr --output $DEVICE --brightness "$(luminance)"
done