chgrp - change group ownership of file
$ chgrp <gid> <path>
$ chgrp <name> <path>
chgrp
called as root or as file owner changes owning group of specified path
to gid
or name
.
# Change group of README.md to 111
# chgrp 111 README.md
# Change group of README.md to root
# chgrp root README.md