ruby_os_platform.rb

module OS
  def windows?
    # use !object.nil? instead of object != nil
    !(/mingw|mswin|cygwin|bccwin|emx/ =~ RUBY_PLATFORM).nil?
  end

  def mac?
    # check for the darwin kernel name
    !(/darwin/ =~ RUBY_PLATFORM).nil?
  end

  def solaris?
    # what if the os was solaris?
    !(/sunos|solaris|bsd/ =~ RUBY_PLATFORM).nil?
  end

  def linux?
    # linux is either defined as linux or arch
    !(/linux|arch/ =~ RUBY_PLATFORM).nil?
  end
  def other?
    !linux? && !mac? && !windows? && !solaris?
  end
  def os
    return "Mac OS X" if mac?
    return "Linux OS" if linux?
    return "Solaris OS" if solaris?
    return "Windows OS" if windows?
    "Strange OS" if other?
  end
end

class JARVIS
  include OS
  def initialize(owner)
    @owner = owner
  end

  def greet
    puts "Hi #{@owner} from #{os}"
  end
end

jar = JARVIS.new("Ahmad Hamdi")
jar.greet