x                  Number of nonidentical conversions performed.
                       Indicates successful conversion. In most
                       cases, 0 is returned.
    (size_t) -1        Indicates an error condition. The function
                       sets errno to one of the following:

                       o  EBADF - The cd argument is not a valid
                          conversion descriptor.

                       o  EILSEQ - The conversion stops when an
                          invalid character detected.

                       o  E2BIG - The conversion stops because of
                          insufficient space in the output buffer.

                       o  EINVAL - The conversion stops because of
                          an incomplete character at the end of the
                          input buffer.