chown owner|{owner group} filelist
              Set  owner  of  each  file  in the list filelist to
              owner, which can be a user name or numeric user id.
              If the first parameter is a list, then the owner is
              set to the first element of the list and the  group
              is set to the second element.  Group can be a group
              name or numeric group id.  If group is {}, then the
              file  group  will  be set to the login group of the
              specified user.

              This command is provided by Extended Tcl.