1) Change group 
The chgrp (from change group) command may be used by unprivileged users on Unix-like systems to change the group associated with a file system object (such as a file, directory, or link) to one of which they are a member. A file system object has 3 sets of access permissions, one set for the owner, one set for the group and one set for others. Cha...
Change Group
Change group ownership, see Section 3.4.2.3.