x                  The number of bytes written.
    -1                 Indicates an error. The file times do not
                       change, and the function sets errno to one of
                       the following values:

                       o  EBADF - The file_desc argument is not a
                          valid file descriptor open for writing.

                       o  EINTR - The write operation was terminated
                          due to the receipt of a signal, and no data
                          was transferred.

                       o  EINVAL - The sum of the iov_len values in
                          the iov array would overflow an ssize_t, or
                          the iovcnt argument was less than or equal
                          to 0, or greater than {IOV_MAX}.

                       o  EIO - A physical I/O error has occurred.

                       o  ENOSPC - There was no free space remaining
                          on the device containing the file.

                       o  EPIPE - An attempt is made to write to a
                          pipe or FIFO that is not open for reading
                          by any process, or that only has one end
                          open. A SIGPIPE signal will also be sent to
                          the thread.