Increase or decrease the brightness of your monitor using arguments to this script

brightness.sh

#!/bin/bash

#############################
#### Author: @TheFlash2k ####
#############################

###########################################################################
###### Change this to the amount of brightness you want to inc/dec ########
base=0.1
###########################################################################

###############################################
############## Requirements: ##################
##### xrandr (For brightness) #################
##### bc     (For basic math) #################
###############################################

RED="\e[31m"
GREEN="\e[32m"
ENDCOLOR="\e[0m"
ERROR="[${RED}-${ENDCOLOR}] ${RED}Error${ENDCOLOR}:"

usage() {

	echo -e $1; echo;

	echo "Usage: $0 [ [UP|DOWN] | NUMBER ]"

	echo "        UP -- Increases the brightness by 0.1"
	echo "      DOWN -- Decreases the brightness by 0.1"
	echo " -h|--help -- Prints the help Menu"
	echo " <NUMBER>  -- Changes the brightness to an exact number (Between 0 to 1)"

	exit $2
}

# Checks if the command exist:
check_command() {
	($1 -h) &>/dev/null
	if [ $? == 127 ] && [ $? != 0 ] && [ $? != 1 ]; then
		echo -e "[${RED}-${ENDCOLOR}] ${RED}$1${ENDCOLOR} command not found."
		exit 1
	fi
}

check() {
	re='0(\.\d+)?|1\.0'
	np_re='(\.\d+)?|1\.0'
	if ! [[ $arg =~ $re ]] ; then
		if ! [[ $arg =~ $np_re ]]; then
	   		usage "[${RED}-${ENDCOLOR}] ${RED}Error${ENDCOLOR}: Invalid value specified! Please specify a value between 0 and 1" 1
	   	fi
	fi
	check_new $arg

}

check_up() {
	res=$(echo "$1>=1"| bc)
	if [[ $res != 0 ]]; then
		echo -e "${ERROR} Cannot increase value to more than 1. (Current: $curr_brightness)"
		exit 1
	fi
}

check_down() {
	## Checking if the value is <= 0:
	res=$(echo "$1<=0"| bc)
	if [[ $res != 0 ]]; then
		echo -e "${ERROR} Cannot decrease value to less than or equal to 0. (Current: $curr_brightness)"
		exit 1
	fi
}

check_new() {
	# This function checks whether the brightness has exceeded the 1 or is equal to or less than 0
	if [[ $2 == "up" ]]; then
		check_up $1
	elif [[ $2 == "down" ]]; then
		check_down $1
	else
		check_up $1
		check_down $1
	fi
}

check_command "xrandr"
check_command "bc"

monitor=$(xrandr --listactivemonitors | cut -d $'\n' -f 2 | cut -d ' ' -f 6)
curr_brightness=$(xrandr --verbose | grep -i brightness | cut -d ' ' -f 2)

# echo "Monitor: $monitor"
# echo "Brightness: $curr_brightness"
# echo "New Brightness: $new_brightness"

if [[ $# != 1 ]]; then
	usage "${ERROR} No/Invalid Arguments have been provided" 1
fi

# Checking the passed arguments:
## Converting the passed argument to lowercase:
arg=$(echo $1 | tr '[:upper:]' '[:lower:]')
if [[ "$arg" ==  "up" ]]; then
	new_brightness=$(echo "$curr_brightness $base" | awk '{print $1+$2}')
	check_new $new_brightness "up"
	echo -e "[${GREEN}+${ENDCOLOR}] Increasing Brightness from $curr_brightness to $new_brightness"
	xrandr --output $monitor --brightness $new_brightness
elif [[ "$arg" == "down" ]]; then
	new_brightness=$(echo "$curr_brightness $base" | awk '{print $1-$2}')
	check_new $new_brightness "down"
	echo -e "[${GREEN}+${ENDCOLOR}] Decreasing Brightness from $curr_brightness to $new_brightness"
	xrandr --output $monitor --brightness $new_brightness
elif [[ "$arg" == "-h" ]]; then
	usage 
elif [[ "$arg" == "--help" ]]; then
	usage
else
	check $1
fi