irb(main):024:0> Open3.popen3('echo helloworld') { |i,o,e,t| t.pid }
NoMethodError: undefined method `pid' for nil:NilClass
        from (irb):24
        from /usr/lib64/ruby/1.8/open3.rb:86:in `popen3'
        from (irb):24
        from :0