problem with gnuplot and octave, 2.9.19, MSVC build on windows XP

[N. B.]

Well, I'm sure now this is a problem with my Windows XP installation: I copied the same toy programs that failed to a clean test installation of XP and they all worked as they should. I wish I knew what caused this, but I don't. But thank you for walking me through this: now I'll reinstall XP and I believe that may actually solve my problems. I'm just glad I didn't claim this is a bug in Octave :), it would be so embarassing! Thanks to Michael and to David for pkg load/unload tip...
Regards,



----- Original Message ----
From: Michael Goffioul <michael.goffioul at gmail.com>
To: N. B. <octavius1907 at yahoo.com>
Cc: help-octave at octave.org
Sent: Tuesday, December 18, 2007 1:31:40 AM
Subject: Re: problem with gnuplot and octave, 2.9.19, MSVC build on windows XP

On 12/17/07, N. B. <octavius1907 at yahoo.com> wrote:
>
> when I type
> DISPLAY
> in the octave prompt, I see that it's *not* defined.
> gnuplot_binary returns
> pgnuplot
>
> Michael, I don't know if this is relevant, but on my system, I tried the
> _popen example on MSDN and no matter what I do, it fails: it returns a null
> FILE*. And popen calls _popen... On the other hand, popen2 does not fail (it
> doesn't work, but it doesn't return a null pointer), and if I'm not
> mistaken, it takes a different route.
> On the MSDN, I tried the _pipe example which does a similar job by via
> _pipe, dup, dup2 (I don't recall if they have underscores) and spawnvp and
> that example works. Does this tell you anything?

Indeed, octave uses internally _popen. So if a simple example does not work
on your system, this might be the reason gnuplot backend is not working.
However, I don't have any idea why _popen would not work. Could you try
to look at GetLastError() returned values after _popen fails in your simple
example. This might give some hints about the reason of the failure.

Michael.


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