Today we explore a "gotcha" interview question from my past:

You accidentally run `chmod -x $(which chmod)`. How do you fix it?

You'll thrash around trying different things, all of which have some arbitrary reason they won't work.

"I'll copy it from another machine." "There are no other machines."

"I'll set the execute bit from python or perl." "There are no interpreters on your machine."

The "correct" answer is to cat the contents of $(which chmod) to another binary you're not using, then execute that.

`cat /bin/chmod > /bin/ping6; mv /bin/ping6 /bin chmod` will sort you out.

The problem is it's trivia, and not really discoverable in an interview scenario.

I do love puzzles like this—on Twitter, when no one’s career is hanging in the balance.

Other “wrong” answers include busybox, rescue partitions, stealing the binary from within a Docker container, and apparently telling the interviewer that it’s a terrible question.