Command:   chgrp - change group
Syntax:    chgrp [-R] [owner:]group file ...
Flags:     -R  Change directory hierarchies
Examples:  chgrp system file1 file2 # Make system the group of the files
           chrgp -R other dir1      # Make other the group of all  files
                                      below dir1

     The group field (and optionally owner field) of the named files  is
changed  to  group and owner.  Alternatively, a decimal gid (uid) may be
specified instead of a group name.  If the -R flag is used, the  changes
will  be applied recursively to all files in named directories. Only the
superuser may execute this command.