From: "A. Sinan Unur" <asu1 AT cornell DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: fread/fwite return value
Date: Sat, 19 Jul 1997 09:34:19 -0400
Organization: Cornell University http://www.cornell.edu
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Nate Eldredge wrote:
> 
> A. Sinan Unur wrote:
> >heretic AT polbox DOT com wrote:
> >> So, I wanted to have error checking and I wrote something like
> >>
> >>  if ( fread(blah,blah,blah) == -1 )
> >>  {
> >>     oh_no_error ();
> >>  }
> >>
> >
> >i think it is an error in the docs. AFAIK, fread is supposed to 
> >return 0, not EOF, precisely because the return value is size_t, and 
> >signifies no bytes read.
> 
> Well, AFAIK, fread is an ANSI function, so the standard should be able 
> to bring enlightenment. Can someone with a copy help us out here?

at the time, i did not have access to any books. anyway, later on i
checked plaugers "the standard C library. the following is an excerpt
from the standard (taken from p248 of that book):

7.9.8.1 The fread function

Synopsis
  #include <stdio.h>
  size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);

...

Returns
  The fread function returns the number of elements successfully read,
which maybe less than nmemb if a read error or EOF is encountered. ...

later on, on p271, plauger remarks:
" ... if the size (second) argument is greater than one, you cannot
determine whether the function also read up to size-1 additional
characters beyond what it reports. As a rule, you are better off calling
the function as fread(buf, 1, size*nmemb, stream) instead of 
fread(buf, size, nmemb, stream)."

i hope this clarifies the confusion i helped create.

the point remains that the docs are wrong in stating that it returns -1
on error. however, it is an even bigger mistake (as was suggested by
someone else during this thread) to suppress the warning that gcc emits
and essentially comparing the return value to (size_t) -1.

i think how to check the return value has already been clarified by art
kagel, but thought i should re-post the quote from the standard.
-- 
   Sinan
 
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