OS detection and TIOCGWINSZ in Ruby

OS.rb

module OS
  class << self
    def windows?
      (/cygwin|mswin|mingw|bccwin|wince|emx/ =~ RUBY_PLATFORM) != nil
    end

    def mac?
      (/darwin/ =~ RUBY_PLATFORM) != nil
    end

    def unix?
      !windows?
    end

    def linux?
      unix? and not mac?
    end
  end

  # Running this C code tells you what TIOCGWINSZ is on your platform:
  #
  # #include <sys/ioctl.h>
  # #include <stdio.h>
  # #include <unistd.h>
  #
  # int main(int argc, char *argv[])
  # {
  #   printf("0x%x\n", (int) TIOCGWINSZ);
  #   return 0;
  # }
  TIOCGWINSZ =
      if mac?
        0x40087468
      elsif windows?
        0x5401
      else
        0x5413
      end
end