From: Simon Strandgaard <0bz63fz3m1qt3001@...>
Date: 2003-05-13T18:50:54+09:00
Subject: Re: RCR for child execution

On Tue, 13 May 2003 17:32:09 +0900, Brian Candler wrote:

> On Tue, May 13, 2003 at 09:48:53AM +0900, Simon Strandgaard wrote:
>> I want users of the editor to be able to use thier own favorite ruby
>> snippets within the editor... *unmodified* ...they don't have to do popen
>> or Open3 or other ackward things for executing their favorite scripts.
>> All Ruby output should go to a text-buffer.
> 
> You mean like irb?
> 
> Maybe you should have a look at the source for FreeRIDE and see how it
> handles this. I haven't installed it, but it sounds like exactly the sort of
> integrated environment you're talking about, so they must have dealt with
> the problem you have encountered.

Yes like irb and FreeRIDE.. But again my environment is completely
differnt. So it doesn't compare well.


[snip code]
> 
> What you have written cannot work:
[snip issues about this pseudo code]

its pseudo code.. And all those issues you pinpoint here is correct.
But never the less I think its the solution :-)

 
> But anyway, I wrote "in the general case", not "in the specific case of
> system() and backtick"
> 
> In the general case, your Ruby program could do lots of things which force
> a direct output to stdout/stderr. Here is one small valid Ruby program:
> 
>         pid = fork do
>           exec("ls /nonexistent")
>         end
>         Process.waitpid(pid)
> 
> How are you going to modify Ruby so that the output of those four lines are
> captured in the sandbox?

All "child-process" routines should parse rb_stdout to the children, in
this case fork.  I know I have only mentioned system&backquote before. 
Well all routines in Rubys Core which spawns children should do this. 

 
> Another example would be
> 
>         require 'ext/someobj'
>         a = Someobj.new.dosomething
> 
> where ext/someobj is a C extension which writes directly to stdout. If your
> editor environment is going to be general-purpose then it better handle that
> case too.

See, You are confusing (A) with (B)
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/71222

 
>> OK.. again assignment to stdout is illegal. freopen should be used instead.
>> Admitted.. I havn't yet tried reopen'ing stdout/stderr :-)
> 
> freopen only lets you associate the FD with a file.
> 
> It would certainly be possible to do
>         STDOUT.reopen("/tmp/capture.out")
> 
> before calling the snippet you are interested in. Then you can close it and
> read the file.

I cannot do this:
  redirect_output('elsewhere') {
       require 'snippet'
  }

its not that simple.. The 'snippet' file contains a class which is
instantiated within C/C++. Therefore the redirection must be permanente.

 
> But that solution is specific to your problem. I don't think it warrants a
> modification to Ruby, the general-purpose programming language, itself.

you are reject this idea.. without understanding my problem first.
Rejections is OK.. but only afterwards :-)


--
Simon Strandgaard