Oracle Script to list space usage per data file

select fn.file_name filename,
       fn.tablespace_name tsname,
       ff.free_space free_space,
       fn.bytes / 1000000 All_space,
       fn.bytes / 1000000 - ff.free_space used_space,
       1 - ff.free_space / (fn.bytes / 1000000) used_pct
  from sys.dba_data_files fn, file_free ff
 where fn.file_id = ff.file_id
 order by used_pct desc ;