fprintfBug

Psychtoolbox › PsychMatlabTests

Mathworks Case ID: 201530, reported 3/19/99

FPRINTF may interpret the first argument as a filename.

Dear Denis,

I am responding to your e-mails of March 19, concerning FPRINTF.

> in my first message (below) i noted that
>
> >fprintf('"%s" hit at time %.3f s\n','5%',1)
> >
> >produces no output at all.
>
> I now discover that FPRINTF created a file called '"%s" hit
> at time %.3f s\n' on my disk, and stored a '5' in it each
> time i executed that statement. Treating the first argument
> of FPRINTF as a file NAME is undocumented, and not what I
> expected.
>
> Can you clarify what Matlab is doing?

Yes, this behavior is due to a bug in the FPRINTF command. For some
reason, passing more than two arguments to FPRINTF can cause the first
argument to be treated as the filename or file ID. This has been reported
to our development staff to be addressed in a future version of Matlab.

As a workaround you can manually specify FID to 1 (for standard output) in
your FPRINTF statement:

a='%04d';
fprintf(1,'ls %s %i\n',a,4);

Another workaround is to make multiple calls to the FPRINTF command. For
example:

a='%04d';
fprintf('ls %s ',a);
fprintf('%d\n',4);

If you have further questions regarding this issue, please be sure to
mention the above case ID number in your e-mail response to me.

Sincerely,

Jeff Mather
Technical Support Engineer
jmather@mathworks.com