Good idea. I'm not sure I know arg parsing libraries in every language though. Even so, hopefully talking about where to make the change and finding some good documentation on an arg parsing library would be good enough start for 20 minutes.
> I'm not sure I know arg parsing libraries in every language though.
In my opinion, you should be free to look that up: that's what you'd do on the job as well. I also google it every time I need to use arg parsing in literally any language because I need it fairly infrequently, and frankly that's how this code came to be: too lazy to look it up again, too easy to write myself, and enjoying the writing of code. Any other solution would also be fine, this test would be about seeing if you can read and write code rather than if you come up with the (what the interviewers think) is the perfect solution.
Yeah, we sometimes say stuff like "we don't expect you to know the arguments to sigaction just like that, you can ask us anything[1] or just put what you think could be reasonable", to make clear we're not looking to hire an encyclopedia.
[1] And if they do, we probably end up pulling up the man page for them because we don't remember either. It's just not the relevant part of any coding interview, the reading or the writing kind.
