The chgrp(1) utility sets the group identifier (ID) of the
file named by each file operand to the group ID
specified by the group operand. If file is a symbolic link,
the group of the file referenced by the symbolic link is changed
unless the -h option is used.
If file is a symbolic link, change the group of the
symbolic link.
-R
Change the group ID for the file hierarchies rooted in the
files instead of just the files themselves.
The group operand can be either a group name from the
group database, or a numeric group ID. If a group name is also a
numeric group ID, the operand is used as a group name.
The user invoking chgrp(1) must belong to the specified
group and be the owner of the file, or have appropriate
privileges.