IIRC, I was using Linux on my PC and from a text console, not a console in the GUI env., when I wrote that one-liner, and once written, it can be put in a scrip

IIRC, I was using Linux on my PC and from a text console, not a console in the GUI env., when I wrote that one-liner, and once written, it can be put in a script with a short name. But didn't know of xkill, thanks.