Script to toggle the screen backlight on and off in Linux

toggleBacklight.sh

#!/bin/bash
# 
# Toggles on and off the screen backlight
# 
# It saves the current brightness value, if there is no previous value, 
# defaults to 1/10th of max brightness
#
# More information in https://diego09310.github.io/linux/2020/02/19/turn-off-dell-xps-screen-linux.html
# 

brightness_path=/sys/class/backlight/intel_backlight/brightness
current_brightness=$(cat $brightness_path)
max_brightness_path=/sys/class/backlight/intel_backlight/max_brightness
max_brightness=$(cat $max_brightness_path)
prev_on_value_path=$(dirname $(realpath $0))/prev_brightness
log_path=$(dirname $(realpath $0))/log.txt
debug=false

log() {
    if [ "$debug" = true ]; then
        echo $@ >> $log_path
    fi
}

set_brightness() {
    log "Setting brightness to $1"
    echo $1 | tee $brightness_path
}

set_previous_brightness() {
    echo $1 | tee $prev_on_value_path
} 
    
if [ "$current_brightness" -eq "0" ]; then
    if [ ! -f "$prev_on_value_path" ]; then
        set_previous_brightness $(( max_brightness / 10 ))
    fi
    set_brightness $(cat $prev_on_value_path)
else
    set_previous_brightness $current_brightness
    set_brightness 0
fi