Setgid
$ ls -l /usr/bin/wall
-rwxr-sr-x 1 root tty 19024 Dec 14 11:45 /usr/bin/wall// Some code$ sudo chmod g+s myfile
$ sudo chmod 2555 myfileLast updated
$ ls -l /usr/bin/wall
-rwxr-sr-x 1 root tty 19024 Dec 14 11:45 /usr/bin/wall// Some code$ sudo chmod g+s myfile
$ sudo chmod 2555 myfileLast updated