chgrp [-fileid] group filelist
          Set the group id of each file in the list  filelist  to
          group,  which  can  be either a group name or a numeric
          group id.

          If the option -fileid is specified, filelist is a  list
          of  open  file  identifiers  rather than a list of file
          names.  This option is not available on all  Unix  sys-
          tems.   Use  the infox have_fchown command to determine
          if this functionality is available.

          The chgrp command is not available on Windows 95/NT.

          This command is provided by Extended Tcl.