Thread Subject: Invalid File identifier on loop

I'm working with Matlab 2009a and have constructed the following simple routine:

fp = fopen('test.txt','w');
for i = 1:50
    fprintf(fp,'%4d hi, i am from hdsc\n',i);
end;
fclose(fp);

This works fine, and creates the file expected. However, when I do the following;
fp = fopen('test.txt','w');
for i = 1:500
    fprintf(fp,'%4d hi, i am from hdsc\n',i);
end;
fclose(fp);


I get the following;

??? Error using ==> fclose
Invalid file identifier. Use fopen to generate a valid file identifier.


What would be causing this

Works fine here.

Dear Scott!

> fp = fopen('test.txt','w');
> for i = 1:50
> fprintf(fp,'%4d hi, i am from hdsc\n',i);
> end;
> fclose(fp);
>
> This works fine, and creates the file expected. However, when I do the following;
> ...
> for i = 1:500
> ...
> ??? Error using ==> fclose
> Invalid file identifier. Use fopen to generate a valid file identifier.

The file identifier can get invalid during writing, if the disk is full or the quota is reached. Nevertheless, the error appears at closing and not during writing. This would mean, that the problem occurs, when the last line is written.
-- This is unlikely!
In addition, you would have more problem, if the disk is completely full.

Another source for this problem might be a TIMER function, which changes the variable "fp" after a certain time, which is by accident exactly the time after the last line has been written. Nevertheless, you would need a DRAWNOW anywhere in the code, to allow the TIMERFCN to operate.
-- Really unlikely!

So I assume, there is a completely other problem in some code, you do not show here.

Good luck, Jan

"Jan Simon" <matlab.THIS_YEAR@nMINUSsimon.de> wrote in message <h1p2ud$2sp$1@fred.mathworks.com>...
> Dear Scott!
>
> > fp = fopen('test.txt','w');
> > for i = 1:50
> > fprintf(fp,'%4d hi, i am from hdsc\n',i);
> > end;
> > fclose(fp);
> >
> > This works fine, and creates the file expected. However, when I do the following;
> > ...
> > for i = 1:500
> > ...
> > ??? Error using ==> fclose
> > Invalid file identifier. Use fopen to generate a valid file identifier.
>
> The file identifier can get invalid during writing, if the disk is full or the quota is reached. Nevertheless, the error appears at closing and not during writing. This would mean, that the problem occurs, when the last line is written.
> -- This is unlikely!
> In addition, you would have more problem, if the disk is completely full.
>
> Another source for this problem might be a TIMER function, which changes the variable "fp" after a certain time, which is by accident exactly the time after the last line has been written. Nevertheless, you would need a DRAWNOW anywhere in the code, to allow the TIMERFCN to operate.
> -- Really unlikely!
>
> So I assume, there is a completely other problem in some code, you do not show here.
>
> Good luck, Jan

Actually, what I posted was the entirety of the code. The disk isn't full, and there aren't quotas. (It is writing to an NFS mount, but that should be no problem).

Dear Scott!

> fp = fopen('test.txt','w');
> for i = 1:50
> fprintf(fp,'%4d hi, i am from hdsc\n',i);
> end;
> fclose(fp);
>
> This works fine, and creates the file expected. However, when I do the following;
> ...
> for i = 1:500
> ...
> ??? Error using ==> fclose
> Invalid file identifier. Use fopen to generate a valid file identifier.

Is it still not solved?! I'm really curious, because something magic must happen!
Did you try to find the minimal number of loops, which invalidates the file pointer? Please insert a "disp(fp)" before FCLOSE, so you could see, if the variable has been changed from anywhere.
It is remarkably, that fp does not loose the validity during writing, but exactly after the last line was written...

Curious, Jan

"Scott " <scott.mohnkern@noaa.gov> wrote in message <h1t8sn$ov9$1@fred.mathworks.com>...
> "Jan Simon" <matlab.THIS_YEAR@nMINUSsimon.de> wrote in message <h1p2ud$2sp$1@fred.mathworks.com>...
> > Dear Scott!
> >
> > > fp = fopen('test.txt','w');
> > > for i = 1:50
> > > fprintf(fp,'%4d hi, i am from hdsc\n',i);
> > > end;
> > > fclose(fp);
> > >
> > > This works fine, and creates the file expected. However, when I do the following;
> > > ...
> > > for i = 1:500
> > > ...
> > > ??? Error using ==> fclose
> > > Invalid file identifier. Use fopen to generate a valid file identifier.
> >
> > The file identifier can get invalid during writing, if the disk is full or the quota is reached. Nevertheless, the error appears at closing and not during writing. This would mean, that the problem occurs, when the last line is written.
> > -- This is unlikely!
> > In addition, you would have more problem, if the disk is completely full.
> >
> > Another source for this problem might be a TIMER function, which changes the variable "fp" after a certain time, which is by accident exactly the time after the last line has been written. Nevertheless, you would need a DRAWNOW anywhere in the code, to allow the TIMERFCN to operate.
> > -- Really unlikely!
> >
> > So I assume, there is a completely other problem in some code, you do not show here.
> >
> > Good luck, Jan
>
> Actually, what I posted was the entirety of the code. The disk isn't full, and there aren't quotas. (It is writing to an NFS mount, but that should be no problem).

Not sure if replying on old posts is of any use: I also had this problem with NFS. On the client, there were no quota's. However, on the NFS server, there were, and that caused the problem.