# File lib/posix/spawn.rb, line 279
    def `(cmd)
      r, w = IO.pipe
      command_and_args = system_command_prefixes + [cmd, {:out => w, r => :close}]
      pid = spawn(*command_and_args)

      if pid > 0
        w.close
        out = r.read
        ::Process.waitpid(pid)
        out
      else
        ''
      end
    ensure
      [r, w].each{ |io| io.close rescue nil }
    end