a simple function using all ANSI-standard functions to determine the size of a file

#include 

long flength(char *fname)
{
      FILE *fptr;
      long length = -1L;

      fptr = fopen(fname, "rb");
      if(fptr != NULL)
      {
            fseek(fptr, 0L, SEEK_END);
            length = ftell(fptr);
            fclose(fptr);
      }

      return length;
}

#ifdef TEST

main(int argc, char *argv[])
{
      printf("Length of %s = %ld\n", argv[0], flength(argv[0]));
      return 0;
}

#endif /* TEST */