chromeos_kbd

#!/bin/bash

set -e

# determine chromeos driver and set as [file] variable
file=/sys/class/leds/chromeos\:\:kbd_backlight/brightness

# read current brightness and set as [cur]
read -r cur < "$file"

# declare [step] and set value
step=$2
: ${step:=10}

# Ansi color code variables
highlight="\e[0;36m"
reset="\e[0m"

# take input and modify [val] as instructed
case "$1" in
  -h|--help) ((val = step));
  echo -e "${highlight}Chromeos_kbd LED backlight v0.0.1a "
  echo -e "(c)Nebletech Industries 2022${reset}"
  echo "Increase or decrease keyboard LED brighness."
  echo "Usage: ${0##*/} --increase num | --decrease num | --set num"
  echo "(--set -s can not currently be used to turn off the backlight)"
  echo "Accepted values for input 1-99"
  exit 0;;
  -i|--increase) ((val = +step));;
  -d|--decrease) ((val = -step));;
  -s|--set) ((val = $2));
  if ((val <   0)); then ((val =   0)); fi
  if ((val > 100)); then ((val = 100)); fi
  printf '%d' "$val" > "$file"
  echo -e "Brightness set to ${highlight}$val%${reset}"
  exit 0;;
esac

# show help screen if no value
if !((val)); then
  echo "Increase or decrease keyboard LED brighness."
  echo "Usage: ${0##*/} --increase num | --decrease num | --set num"
  exit 0
fi

#set [val] to [cur]+[val]
((val = cur + val))

# prevent value going beyond limits
if ((val <   0)); then ((val =   0)); fi
if ((val > 100)); then ((val = 100)); fi

#print value to driver
printf '%d' "$val" > "$file"
echo -e "Brightness set to ${highlight}$val%${reset}"

exit 0