n                  The number of bytes read.
    -1                 Upon failure, the file pointer remains
                       unchanged and pread sets errno to one of the
                       following values:

                       o  EINVAL - The offset argument is invalid.
                          The value is negative.

                       o  EOVERFLOW - The file is a regular file, and
                          an attempt was made to read or write at or
                          beyond the offset maximum associated with
                          the file.

                       o  ENXIO - A request was outside the
                          capabilities of the device.

                       o  ESPIPE - fildes is associated with a pipe
                          or FIFO.