Return_Values

   x                  Pointer to a passwd structure, if successful.
   NULL               Indicates an end-of-file or error occurred.
                      The function sets errno to one of the
                      following values:

                      o  EIO - Indicates that an I/O error occurred
                         or the user does not have appropriate
                         privileges enabled to access the user
                         authorization file (SYSUAF).

                      o  EMFILE - OPEN_MAX file descriptors are
                         currently open in the calling process.

                      o  ENFILE - The maximum allowable number of
                         files is currently open in the system.