From: Alain Magloire <alainm AT rcsm DOT ece DOT mcgill DOT ca>
Message-Id: <199903020302.WAA09354@mccoy2.ECE.McGill.CA>
Subject: Re: inetutils
To: eliz AT is DOT elta DOT co DOT il (Eli Zaretskii)
Date: Mon, 1 Mar 1999 22:02:58 -0500 (EST)
Cc: djgpp-workers AT delorie DOT com
In-Reply-To: <Pine.SUN.3.91.990301112312.2578F-100000@is> from "Eli Zaretskii" at Mar 1, 99 11:23:32 am
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Reply-To: djgpp-workers AT delorie DOT com

Bonjour 

> So you will need to do something like this:
> 
>   system ("start.exe /m redir -i input -o output -e error foo.exe");
> 
> ("redir" is a standard program that comes with DJGPP.)
> 
> This still has some problems, like passing the environment variables
> (we could change "redir" to read them from a file), and the
> redirection will not work in certain cases, like when the parent and
> the child try to write to the same file, because Windows generally
> prevents two programs from writing to the same file.
> 

But let me explain briefly, inetutils is a collection of servers
and clients. The servers are all spawn by the superdaemon inetd.
Inetd after accept()ing a connection set the stage to run the server :
select(); fd = accept(); pid = fork() 
pid == 0 {
  dup2(fd, 0); dup2(fd, 1) dup2(fd, 2); exec("ftpd/telnetd/rlogind ..");
}
...
sigaction (SIGCHLD) ==> wait3("reaped child")

The std{in,out,err} are sockets handles. And in fact the code
is full of fgets()/putc() etc .. all servers take for granted
that the std I/O are redirected.

The problem with system() is that I don't have the pid for the wait
but if I read your post right doing a waitpid() after a start /m
is meaningless.

Passing file descriptors to another processes is sometimes
supported via ioctl(). But I don't think it exists on DJGPP.

A cleaner solution would be to have the SVR4 interface of
/dev/fd/n
where n is the file descriptor.
for example :
/dev/fd/0 --> stdin
/dev/fd/1 --> stdout etc ..

so one could do :
redir -i /dev/fd/123 -o /dev/fd/123 -e /dev/13 ftpd.exe 

Or maybe reserve the namespace "/dev/tcp" for the networking library.
So /dev/tcp/xxx could be use to pass handle around.

I don't know enough about DJGPP nor libsocket to see if
this is feasible.

-- 
au revoir, alain
----
Aussi haut que l'on soit assis, on est toujours assis que sur son cul !!!