From bug-octave-request at bevo dot che dot wisc dot edu  Thu Sep 23 19:59:10 1999
Subject: Re: Cleanup after fork
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: aking at math dot arizona dot edu
Cc: bug-octave at bevo dot che dot wisc dot edu
Date: Thu, 23 Sep 1999 19:58:02 -0500 (CDT)

On 23-Sep-1999, Aaron King <aking at math dot arizona dot edu> wrote:

| Sorry,  I should have said "asynchronous mode" instead of
| "synchronous".  Try this: 
| 
|     x = (0:0.01:2*pi)';
|     plot(x, sin(x));
|     system("ls", 1, "async");
|     replot
| 
|     gnuplot> pl "/tmp/oct-11267aaa" t "line 1"
|                       ^
|            can't read data file "/tmp/oct-11267aaa"
|            line 0: (No such file or directory)

OK, I see the problem now.

| The temporary file (in this case in /tmp) has been deleted, not when
| one program is replaced by another (using exec) but when that second
| program exits.  I'm imagining an option (set in the .octaverc file,
| for example), which when = 0 prevents the cleanup from being
| registered with atexit.

I don't think an option is needed, because this just seems like wrong
behavior to me.  Here is a patch to try.  Your line numbers will
probably be different.

Obviously, this will only work on systems with /bin/sh, so eventually
some other fix needs to be found.

Thanks,

jwe


Thu Sep 23 19:49:36 1999  John W. Eaton  <jwe at bevo dot che dot wisc dot edu>

	* toplev.cc (Fsystem): For async case, use execl instead of
	system, avoiding the need to exit after executing the subprocess.


*** octave-2.0.14/src/toplev.cc	Tue Nov 17 14:33:38 1998
--- src/toplev.cc	Thu Sep 23 19:43:52 1999
***************
*** 842,850 ****
  		error ("system: fork failed -- can't create child process");
  	      else if (pid == 0)
  		{
! 		  system (cmd_str.c_str ());
! 		  exit (0);
! 		  retval(0) = 0.0;
  		}
  	      else
  		retval(0) = (double) pid;
--- 821,829 ----
  		error ("system: fork failed -- can't create child process");
  	      else if (pid == 0)
  		{
! 		  execl ("/bin/sh", "sh", "-c", cmd_str.c_str (), 0);
! 
! 		  panic_impossible ();
  		}
  	      else
  		retval(0) = (double) pid;



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