Force Quit an Unresponsive Graphical Application in Ubuntu

“There are lots of command-line utilities to kill unresponsive
programs in Linux, but for the button-pushing-inclined, the Force
Quit panel button lets you kill any app that you can click on
without needing to remember anything.

“We’re not exaggerating about the amount of ways you can kill
applications in Linux – we’ve covered three previously.
However, this method has a few advantages: first, it’s incredibly
easy – you just have to click a button and click on the
frozen application. Second, in our testing, it’s been slightly more
reliable in shutting down unresponsive GUI applications than other
solutions like xkill. On the flip side, it won’t work at all for
non-graphical programs.”

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