Return_Values

   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.