0                  Successful completion.
    -1                 Indicates an error. errno is set to one of the
                       following:

                       o  EBADF - The file descriptor parameter
                          contains an invalid value.

                       o  EIO - An I/O error occurred while reading
                          the device.

                       o  EINTR - A signal was intercepted during
                          execution of the function.

                       o  EOVERFLOW - One of the values to be
                          returned cannot be represented correctly
                          in the structure pointed to by buffer.