From: Robert Klemme <bob.news@...>
Date: 2003-05-20T01:05:29+09:00
Subject: Re: select strange behavier


"Simon Strandgaard" <0bz63fz3m1qt3001@sneakemail.com> schrieb im
Newsbeitrag news:pan.2003.05.19.01.12.43.69731@sneakemail.com...
> replacement for 'Kernel#system' which captures all output.
> This is the *almost* final version.. this may have others interest :-)
> Warning: 'stdin' is not yet supported.
>
> Suggestions for improvements is welcome.

Some minor (see lines without leading "> ") and a question: did you check
that this works on windows, too?  I recently ran into a problem with pipes
on windows.  Apparently they can't be used for multiplexing...

> def system(command, *args)
>     #todo: stdin
>     r1, w1 = IO.pipe # stdout
>     r2, w2 = IO.pipe # stderr
    thread = Thread.new(r1,w1,r2,w2) do |r1,w1,r2,w2|
      fdes = [r1, r2]
>         loop do
>             #puts "waiting"
>             res = select(fdes, nil, nil, nil)[0]
>             #p res
>             if res.include?(r1)
>                 #puts "r1"
>                 unless r1.eof
>                     Redir.instance.write_out r1.read
>                 else
>                     #puts "kill r1"
>                     fdes.delete r1
>                     thread.kill if fdes == []
>                 end
>             end
>             if res.include?(r2)
>                 #puts "r2"
>                 unless r2.eof
>                     Redir.instance.write_error r2.read
>                 else
>                     #puts "kill r2"
>                     fdes.delete r2
>                     thread.kill if fdes == []
>                 end
>             end
>         end
>     end
>     pid = Kernel.fork do
>         r1.close; r2.close
>         $defout.reopen(w1); $stdout.reopen(w1); $stderr.reopen(w2)
>         exec(command, *args)
>         # todo: should I care closing w1+w2 correctly?
>     end
>     w1.close; w2.close
>     status = Process.waitpid2(pid, 0)
>     # wait until EOF on both pipes (r1+r2)
>     thread.join
>     r1.close; r2.close
>
>     #$? = status[1]  # not possible
    (status[1] == 0)
> end

And I'd try to put the "close" calls into "ensure" blocks where possible.

Regards

    robert