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To: Francois Felix Ingrand <felix AT dial DOT oleane DOT com>
cc: gnu-win32 AT cygnus DOT com
Subject: Re: Problem with socketpair/fork/dup2/fdopen b20 
In-reply-to: Your message of "06 Feb 1999 13:56:28 +0100."
             <8690ebsnb7 DOT fsf AT dial DOT oleane DOT com> 
Date: Sat, 06 Feb 1999 16:19:37 -0600
From: Mumit Khan <khan AT xraylith DOT wisc DOT EDU>

Francois Felix Ingrand <felix AT dial DOT oleane DOT com> writes:
> 
> I cannot get this to work.
> 
> fdopen returns NULL and perror a bad file descriptor... which would suggest
> that dup2 did not duplicate stdout in sp[1]...

[ .. snippet of example code ... ]

Hi Francois,

I have code that does similar thing and it works on Cygwin as it does on
every POSIX-type system I've run it on.

Unless someone can spot something weird, you'll need to supply standalone 
code that we can compile and run. I'm not sure I understand your
logic behind dup'ing stdin/stdout and then fdopen for read/write in the
child, but that's probably because I don't know what your code really
does.

I suggest you chop it down to the smallest size possible and repost as a
bug report.

Regards,
Mumit


> 
> It work under Solaris and other Unices...
> 
> void call_propice_cat(char *log_file)
> {
>      int pid, sp[2];
> 
>      if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) {
> 	  perror("call_propice: socketpair");
> 	  exit(1);
>      }
>      fcntl(sp[1], F_SETFD, 1);      /* this is to avoid that the ns will be d
> up when we fork */
>      
>      if ((pid = fork()) < 0) {
> 	  perror("fork");
> 	  exit(1);
>      }
> 
>      if (pid) {			/* The father */
> 	  close(sp[0]);		/* Close one side */
> 	  fcntl(sp[1], F_SETFL, FNDELAY); /* I am not sure this is required... 
> */
> 	  if (dup2(sp[1],1) < 0)
> 	       perror("call_propice_cat:dup2");	/* Get stdout plug on sp[1] */
> 	  /* dup2(sp[1],2);    Get stderr plug on sp[1] */
> 
> 	  propicefp = (FILE *)fdopen(sp[1], "r+");
> 	  if (! propicefp) 
> 	       perror("call_propice_cat:fdopen");	/* Get stdout plug on
> 							   sp[1] */
> 	  setbuf(propicefp, NULL);
> 
> 	  propiceInputId = XtAppAddInput(app_context, sp[1], (XtPointer)XtInput
> ReadMask, read_propice, NULL);
>      } else {			/* The child */
> 
> -- 
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> "J'en ai cauchemarde... Microsoft l'a fait."
> Professional: http://www.laas.fr/~felix         mailto:felix AT laas DOT fr
> Personal: http://worldserver.oleane.com/felix   mailto:felix AT dial DOT oleane DOT com
> 
> 
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