> This doesn't work reliably because the arguments are wrong. It's "fread(buf, size_of_item, number_of_items, file_ptr)".

No it isn't. What C standard library are you using? Above code is correct in my C standard library ... man fread:

  SYNOPSIS
        #include <stdio.h>
        size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
        ....
        The function fread() reads nmemb items of data, each size bytes long, from the stream pointed to by stream, storing them at the location given by ptr.