Fix the unit test and open a giant hole everywhere
So the funny thing is, when I saw that problem description, my first thought was: "oh, that's what mkdir -p does; I wonder if it would be easier to just shell out to that than try and implement it yourself". I grant that that implementation is a massive SQL-injection-like vulnerability, but I'm still not 100% convinced that the basic impulse is wrong; I can easily imagine an alternate universe where the second half of this blog post is talking about how someone wrote it themselves and introduced some subtle bug that the coreutils folks fixed 20 years ago and everyone else has to painfully rediscover. I wonder if any of the major implementations are friendly to being used as a library? Obviously then you have to deal with licensing issues, which is a catch. Maybe fork+exec? I dunno, I'm just trying to feel out whether there's a middle ground between system() and rewriting functionality that someone else has written and that's been used by a billion other users for decades.