Change the group of one or more files to newgroup. newgroup is either a group ID number or a group name located in /etc/group. Only the owner of a file or a privileged user may change the group.
Print information about files that are changed.
Do not print error messages about files that cannot be changed.
Print help message and then exit.
Traverse subdirectories recursively, applying changes.
Change the group to that associated with filename. In this case, newgroup is not specified.
Verbosely describe ownership changes.
Print version information and then exit.