Wladimir PalantAs I'm waiting for a vendor to publish their announcement, I don't want to rely on them notifying me timely (this never worked before), nor do I want to hammer their website manually. Luckily, I found the #urlwatch tool which does the job nicely: https://thp.io/2008/urlwatch/
On Ubuntu this tool can even be installed via apt. The process of adding pages to be checked to ~/.config/urlwatch/urls.yaml is pretty straightforward (even with CSS-based filter for the relevant part). One can then run urlwatch regularly via cron and it will report any changes.
Configuring reporters is somewhat less obvious. First of all, reporters are configured globally in ~/.config/urlwatch/urlwatch.yaml and not per job as I expected. And second, there is no built-in reporter which will simply run a custom command, e.g. to display a graphic message.
Luckily, adding a reporter is fairly simple. One can create a ~/.config/urlwatch/hooks.py script, e.g. with the contents below (using kdialog command line tool to display a message).
And then one only needs to enable this reporter in ~/.config/urlwatch/urlwatch.yaml.
Don't forget to set DISPLAY=:0 when running urlwatch via cron!
RenalCalculus@WPalant setting DISPLAY=0 makes assumptions about the system that may not be true, i.e. the user running cron owning the X11 display.
@renalcalculus Sure, this is a simplification. But I think that anybody who will actually attempt to follow these steps will know if the underlying assumptions aren't right for them.