chgrp – command changes the owner group of one or more files.
chgrp [-cfvR] group files
-c displays only files with modified group owner.
-f suppress error messages.
-v detailed reports on the changes the group owner.
-R recursively changes the group ownership of files in all subdirectories.
To change the group owner of one or more files, type chgrp group name, and after him – the names of files (group owner can also changed and by command chown).