Guix

clipnotify is a simple program that, using the XFIXES extension to X11, waits until a new selection is available and then exits.

It was primarily designed for clipmenu, to avoid polling for new selections.

clipnotify doesn't try to print anything about the contents of the selection, it just exits when it changes. This is intentional -- X11's selection API is verging on the insane, and there are plenty of others who have already lost their sanity to bring us xclip/xsel/etc. Use one of those tools to complement clipnotify.