Below script is written for managing brightness value of my computer. I have written this just to play with bash shell scripting. It is purly for learning purpose.

brightness

#!/bin/bash

path=/sys/class/backlight/radeon_bl0/brightness

display_usage() {
  cat << EOF
  Usage: brightness [-h] VALUE
  Set the screen brightness according to given value.

  -h     Will display the help.

  VALUE  Screen brightness value strictly between 0 to 100.

EOF
}

while getopts h option
do
  case $option in
    h)
      display_usage
      exit 0
      ;;
    *)
      display_usage
      exit 1
      ;;
  esac
done

brightness=$1

if [[ "$brightness" = +([0-9]) ]] && ((brightness >= 0 && brightness <= 100))
then
  sudo tee "$path" > /dev/null <<< "$brightness"
else
  echo "ERROR: The brightness value should be interger between 0 to 100. See usage by 'brightness -h'"
  exit 1
fi