# File lib/notify.rb, line 5
  def self.which(prog, path=ENV['PATH'])
    if RUBY_PLATFORM.downcase =~ /mswin(?!ce)|mingw|bccwin|cygwin/
      path.split(File::PATH_SEPARATOR).each {|dir|
        f = File.join(dir,prog+".exe")
        return f if File.executable?(File.join(f)) && !File.directory?(f)
      }
      nil
    else
      return system("which #{prog} > /dev/null 2>&1")
    end
  end