# File lib/session.rb, line 630
      def tmpfifo
        path = nil
        42.times do |i|
          tpath = File::join(Dir::tmpdir, "#{ $$ }.#{ rand }.#{ i }")
          v = $VERBOSE
          begin
            $VERBOSE = nil
            system "mkfifo #{ tpath }"
          ensure
            $VERBOSE = v 
          end
          next unless $? == 0
          path = tpath
          at_exit{ File::unlink(path) rescue STDERR.puts("rm <#{ path }> failed") }
          break
        end
        raise "could not generate tmpfifo" unless path
        path
      end