Interesting how the author was looking at "cd" obviously sourced from FreeBSD project (perhaps found on a Mac computer running XNU kernel) and then, to investigate further, she consulted the source code for the Linux kernel to learn about "the" chdir syscall.

Would the title "How does 'cd' work in MacOS?" be better for readers wishing to learn, or worse? I wonder.

The blog posts from her friend at jvns.ca have been similarly Linux-centric but never use titles that inform the reader as such, i.e., "How does X work?" versus "How does X work in Linux?"

It makes me ask, how important is it for students to be aware of the Holy Grail of UNIX: portability.

How long should one remain blissfully ignorant of incompatibilities between UNIX-like OS that work against those "still seeking the Holy Grail"?

As a user, the UNIX programmers I admire the most are the ones who understand the value of portability, set it as a goal and through broad knowledge and utmost care can get very close to achieving it, despite the mind-numbing work or the tradeoffs this might entail.