chgrp sets the group ID of the file.

-f	force ignores errors, except for usage errors and doesn't query about strange modes (unless the user does not have proper permissions).
-R	Change the group ID for the file hierarchies rooted in the files instead of just the files themselves.
With -R:	override each other and the last one specified is used.
-RP	symbolic links are prevented from being followed. default.
-RL	all symbolic links are followed.
-RH	symbolic links on the command are followed but not those encountered in the tree traversal
-h	For symbolic link, the group ID of the link is changed not the target.
-v	verbose, shows files as modified.

group can be a group name or group ID.

The user invoking chgrp must belong to the group and be the owner of the file, or be the super-user.
exits 0 on success, and >0 if an error occurs.
-v is non-standard and its use in scripts is not recommended.

FILES
/etc/group group ID file

SEE
chown(2), fts(3), group(5), passwd(5), symlink(7), chown(8)