x                  The number of bytes written, excluding the
                       null terminator.
    Negative value     Indicates an error. The function sets errno to
                       one of the following:

                       o  EILSEQ - Invalid character detected.

                       o  EINVAL - Insufficient arguments.

                       o  ENOMEM - Not enough memory available for
                          conversion.

                       o  ERANGE - Floating-point calculations
                          overflow.

                       o  EVMSERR - Nontranslatable OpenVMS error.
                          vaxc$errno contains the OpenVMS error code.
                          This might indicate that conversion to a
                          numeric value failed because of overflow.

                       The function can also set errno to the
                       following as a result of errors returned from
                       the I/O subsystem:

                       o  EBADF - The file descriptor is not valid.

                       o  EIO - I/O error.

                       o  ENOSPC - No free space on the device
                          containing the file.

                       o  ENXIO - Device does not exist.

                       o  EPIPE - Broken pipe.

                       o  ESPIPE - Illegal seek in a file opened for
                          append.

                       o  EVMSERR - Nontranslatable OpenVMS error.
                          vaxc$errno contains the OpenVMS error code.
                          This indicates that an I/O error occurred
                          for which there is no equivalent C error
                          code.