gnuplot-beta

wgnuplot log errors to a file

[Tim H. <tim...@un...>]

Hello,

I am calling wgnuplot from an external program. Since there is no error 
stream attached one cannot receive error messages. The exit code just 
indicates that there is an error but not which. Therefore it would help, 
if there was an option to write errors to a file, e.g.:

wgnuplot -log error.log

I think it should be quite simple. One could intercept the error 
messages in MyFPrintF and similar functions.

Before starting to implement, I would like to have some comments on the 
idea form more experienced gnuplot developers.

Thanks,
Tim

Re: wgnuplot log errors to a file

[Ethan M. <merritt@u.washington.edu>]

On Wednesday 28 May 2008, Tim Hoffmann wrote:
> Hello,
>
> I am calling wgnuplot from an external program. Since there is no error
> stream attached one cannot receive error messages. 

Errors are sent to stderr, the usual error stream.  In a normal operating
environment (which may exclude MSWindows) you can receive the
messages just fine.

> The exit code just 
> indicates that there is an error but not which. 

The current CVS version also stores the most recent error message in the
variable GPVAL_ERRMSG.  You can print it to a file if you want to.

> Therefore it would help, 
> if there was an option to write errors to a file, e.g.:
>
> wgnuplot -log error.log
>
> I think it should be quite simple. One could intercept the error
> messages in MyFPrintF and similar functions.
>
> Before starting to implement, I would like to have some comments on the
> idea form more experienced gnuplot developers.

I am not sure there are any such people, with regard to Windows development.
I gather that the Windows user interface (by which I mean Windows itself, 
not the gnuplot GUI) is fundamentally different from the stdin/stout/stderr
model used by gnuplot and pretty much all other unix or C programs.

-- 
Ethan Merritt
(on the road)

Re: wgnuplot log errors to a file

[Allin C. <cot...@wf...>]

On Wed, 28 May 2008, Tim Hoffmann wrote:

> I am calling wgnuplot from an external program. Since there is no error 
> stream attached one cannot receive error messages. The exit code just 
> indicates that there is an error but not which. Therefore it would help, 
> if there was an option to write errors to a file, e.g.:
> 
> wgnuplot -log error.log

What happens if you do 

wgnuplot 2>error.log

That's supposed to work for win32 console programs at least.

Allin Cottrell

Re: wgnuplot log errors to a file

[Tim H. <tim...@un...>]

Allin Cottrell wrote:
 > On Wed, 28 May 2008, Tim Hoffmann wrote:
 > wgnuplot 2>error.log
 >
 > That's supposed to work for win32 console programs at least.
Right, but since wgnuplot is not a console program it does not. I tried 
but it creates just empty log files. As far as I could figure out, a 
WIN32 GUI application silently throws away everything written to stderr! 
However one can create a new console and redirect output to it. But it 
appears to be impossible to redirect it to the calling console.

On the other hand, you could make it a console application and start the 
window yourself. But then you'll have a console poping up when you start 
the program from the menu.

I think it's the same reason why there has to be pgnuplot.exe for piped 
input.

So I suppose, a log file is the best choice in this case.


Tim