This command exists since Tk 8.4 and sets or retrieves window-specific attributes. The command is different for each platform. I know the possible options for Windows98 and it seems there are no options to this command with Linux.
Windows (98) options:
All options take a true/false value
-toolwindow makes a window with a single close-button (which is smaller than usual) on the right of the title bar
-topmost makes sure the window always stays on top of all other windows
-disabled makes it impossible to interact with the window and redraws the focus
Example retrieving the default values:
% wm attributes . -disabled 0 -toolwindow 0 -topmost 0
RS confirms that this applies to Windows 2000 too.
Peter Lewerin WinXP too.