Changes the group associated with a file
chgrp [options] group file-list
chgrp [options] --reference=rfile file-list
The chgrp utility changes the group associated with a file. See page 1108 for information on how chown can change the group associated with, as well as the owner of, a file.
The group is the name or numeric group ID of the new group. The file-list is a list of pathnames of the files whose group association you want to change. The rfile is the pathname of a file whose group is to become the new group associated with file-list.
-c Displays a message for each file whose group was changed.
--quiet or --silent
-f Causes chgrp not to display warning messages about files whose permissions prevent you ...