Steve Litt <slitt@???> writes:

[...]

> Another suggestion, if you'd like to use C, is the libsx package: VERY
> lightweight GUI. Here's a no-systemd notification system, using libsx,
> that a guy on Debian-User wrote:
>
> http://a3b3.com/stuff/sxnotify.c
>
> The preceding link has detailed build instructions.

If you want a way to show a popup with a string in it using Athena
widgets, you might want to have a look at the xmessage program.