From: Simon Strandgaard <0bz63fz3m1qt3001@...>
Date: 2003-05-08T07:26:54+09:00
Subject: Re: capture output

On Thu, 08 May 2003 07:58:18 +0900, Brian Candler wrote:

> On Wed, May 07, 2003 at 10:58:38PM +0900, Simon Strandgaard wrote:
>> [snip popen talk]
>> 
>> Sorry.. I never thought it would be that hard to explain 
>> my problem :-)
>> 
>> 
>> I embed ruby into C++.  The "void main" is located in the frontend.
>> Right now everything is running in the same process. 
>> 
>> User supplyed ruby-code is executed in the same process...
>> its NOT executed as a child-process, thus popen3 is not possible.
> 
> Fine, but you were the one who gave the example of "vim running a process
> and capturing its output". That is most definitely a child process.

Agree. Sorry for the "bad" parallel.


> If you have written a C++ program, and have embedded the Ruby interpreter in
> it, then by default they will share the same stdin/stdout/stderr. The Ruby
> code can also write to stdout and stderr. Why should it not?

I have a *ncurses* frontend for my editor. If ruby outputs data to
stdout/stderr then the console gets messed up.

 
> If you want to intercept it, so that when Ruby does "puts" it goes into a
> string, then you can redirect Ruby's output stream as explained before:
> 
>     $defout = StringIO.new(...)
>     puts "Hello"

yes exactly.

 
> If the Ruby process spawns a child, using backtick or Kernel#system, THEN IT
> IS A CHILD of your C++ program (the parent process is one and the same). If
> you don't use popen then it will share the same Unix file descriptors for
> stdout and stderr. This is how Unix works.

YES - now i understand. You have teached me well :-) 
This is actually where the problem lies.. how can I be that silly. 
I think I can handle it from here (setup some pipes in C++). 

I will add this to the ruby-embed-into-c++ tutorial
http://metaeditor.sf.net/embed/


[snip]
> 
> I'm sorry, frustration is starting to set in for me. For my sanity I think I
> will have to ignore this thread now.

Thanks for everything... You have provided me with much important
knowledge. I am sorry for being mean to you.. but that because I 
recenly switched to the dark side (soon I'll be in the-matrix mode).

--
Simon Strandgaard