chgrp - change group ownership of files
$ chgrp <gid> <path...>
$ chgrp <name> <path...>
chgrp called as root or as file owner changes owning group of specified path to gid or name.
-h, --no-dereference: Don't follow symlinks# Change group of README.md to 111
# chgrp 111 README.md
# Change group of README.md to root
# chgrp root README.md