The letters `rwxXstugo' select the new permissions for the
       affected users: read (r), write (w),  execute  (or  access
       for directories) (x), execute only if the file is a direc­
       tory or already has execute permission for some user  (X),
       set  user  or group ID on execution (s), save program text
       on swap device (t), the permissions that the user who owns
       the  file  currently  has for it (u), the permissions that
       other users in the file's group have for it (g),  and  the
       permissions  that other users not in the file's group have
       for it (o).