All files put into a folder "foo" by user "a" or "b" should belong to the "bar" group and only be visible by them

Question

Pre requisite steps:

1. Create two new user accounts "a" and "b"

   # useradd a
   # useradd b
   

2. Create a group "bar". Create a directory "foo".

   # groupadd bar
   # mkdir /tmp/foo
   

Task:

All files put into the "foo" directory by users "a" or "b" should belong to the "bar" group and be only visible by them.

Answer 1

chgrp bar /tmp/foo [changes the group ownership of foo to bar due to which everything added to foo will belong to bar]

You can also set ACL permissions as:

setfacl -m u:a:rwx /tmp/foo