!!!
r - 4
w - 2
x - 1


s
S - s + x (which is hidden)
t - sticky (+ x which is hidden)

SUID - set user id
SGID - set group id
Sticky - for files - disable caching (for DB files for example). Don't used at Linux
         for dirs  - (if I have write to any dir - I can delete files from it)
                     user can't delete files from catalog if he does not own the mentioned files


umask - process attribute
    mask that subtract access permissions
    default - 022 (files - 644, dirs - 755)