x                  getpwnam returns a pointer to a valid passwd
                       structure, if a matching entry is found.
    NULL               getpwnam returns NULL if an error occurred
                       or a the specified entry was not found. errno
                       is set to indicate the error. The getpwnam
                       function may fail if:

                       o  EIO - An I/O error has occurred.

                       o  EINTR - A signal was intercepted during
                          getpwnam.

                       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.

    0                  When successful, getpwnam_r returns 0 and
                       stores a pointer to the updated passwd
                       structure at the location pointed to by
                       result.
    0                  When unsuccessful (on error or if the
                       requested entry is not found), getpwnam_r
                       returns 0 and stores a NULL pointer at the
                       location pointed to by result. The getpwnam_r
                       function may fail if:

                       o  ERANGE - Insufficient storage was supplied
                          through buffer and bufsize to contain the
                          data to be referenced by the resulting
                          passwd structure.