From: Brian Candler <B.Candler@...>
Date: 2003-05-14T08:08:59+09:00
Subject: Re: RCR for child execution

On Tue, May 13, 2003 at 11:33:10PM +0900, Simon Strandgaard wrote:
> Kernel#fork  does spawn a child.. changes to Rubys Core is necessary.
> unix-fork inherit stdin/stdout/stderr from parent to the child process.
> I want Rubys Kernel#fork to inherit rb_stdin/rb_stdout/rb_stderr from the
> parent to the child process. 
> But hey.. unix-fork() does not take any arguments.  Is this possible?
> My guess - Yes this should be possible. Here is some pseudo code.
> 
> void Kernel#fork() {
>     backup_stdout = stdout;      /* what i want */
>     stdout = rb_stdout;          /* what i want */
>     pid = fork();
>     if(pid == 0)
>         stdout = backup_stdout;  /* what i want */
> }

That pseudo-code doesn't make sense: a Ruby object cannot be assigned to a
FILE*, nor can it be put in the Unix file descriptor table.

> This way stdout/stderr/stdin should be untouched and remain usable in the C/C++
> application.
> 
> Does it answer the question ?

No, because it cannot work. If I write

     s = ""
     $stdout = StringIO.new(s)
     pid = fork do
       exec("ls *.txt")
     end
     Process.wait(pid)

how are you going to modify fork or exec so that it captures the output of
'ls' into the StringIO object created earlier?

Brian.