Maybe, but that doesn't sound like my interview at Google, which was interesting but really rather random. Perhaps most notably, one interviewer became irate that I didn't know the "ps -o" flags off of the top of my head. :-/
But the real magic comes when they run out. What do they do then? Good people say that they don't know. Often, they will take guesses at a few more based on general principles. E.g., "I'm sure there are arguments for sorting, but I only use top for that." Or, "There must be more ways to filter, but I only do it by user or command." They'll usually look a bit uncomfortable, because they are the sort of person who likes knowing things. But what they won't do is bluff or make things up.
And honestly, that's my biggest tip for hiring: find people who like understanding things and know a good amount for their level, but are willing to say when they don't know. People who can't do that are dangerous.
Again, this is one of those, "Here's what I've got cached, and here's where I'd look up what I don't know offhand" questions.
From the ps manpage:
Note that "ps -aux" is distinct from "ps aux". The POSIX and UNIX standards require that "ps -aux" print all processes owned by a user named "x", as well as printing all processes that would be selected by the -a option. If the user named "x" does not exist, this ps may interpret the command as "ps aux" instead and print a warning. This behavior is intended to aid in transitioning old scripts and habits. It is fragile, subject to change, and thus should not be relied upon.
Try it next time you're mingling with ops people. Say in a bar at a conference. Don't look at what they answer. Look at how they answer. Some people are comfortable not knowing. Some people are excited to discover the ones they forgot they knew. some people get curious and eager to fill the hole they've just noticed in their knowledge. And some people get defensive and peevish.
I don't score it by how many option-letters people know. I score it by how well they demonstrate familiarity with a basic ops activity, which is finding out what's running.
Even if somebody said they never used ps, or like below, only use one incantation, that isn't a problem, because my follow-up there would be to ask how you'd find out what's using all the RAM or what's using a lot of CPU.
Maybe they're just used to using different tools, in which case I can ask for details for those tools. (And then check manually later to make sure I'm not getting snowed.) But if they've done a bunch of ops stuff, they'll demonstrate the sort of know-from-doing level of familiarity with something.
In theory I could just ask the broader question to start. But some people are good talkers, and I'm looking for evidence that people are good doers. All that said, I've shifted mainly to more experiential interview processes, as actually doing is the best way to see if somebody's a doer.
So the process is, in fact, designed to make people feel uncomfortable, for a little bit (or at least you're definitely aware that this is a frequently occurring side effect).
Does that not suggest to you that there may be a negative tradeoff at play here? (To wit: yes you do manage do efficiently extract a few bits of information from them... but at cost of having them feel like they're being, well... interrogated. And are already "losing points" by that point in the conversation with you).
I had a PM friend who would try to push the bounds of a candidate's knowledge until they gave up and said "I don't know". The actual knowledge wasn't the point of the question: it was that they could say "I don't know", because PMs who can't tend to make life miserable for the engineers & other teammates who work with them.
And I agree with your PM friend; I think willingness to admit ignorance is even more valuable there.
But no, I don't think they walk away feeling interrogated. My style is pretty conversational, and when people don't have all the answers, I definitely work to make them feel comfortable with that. E.g., for this question I'd close with something like, "Of course nobody knows all the arguments to ls. I sure don't. So you did fine."
To me any question where the obvious answer is "I can trivially look all that up in the man pages" is a gigantic red flag that I don't want to work at that place.
If I'm feeling curious that day, I might begin a conversation about what you think you are testing for with that question, as I've spent a fair bit of my career studying hiring pipelines. But if I hadn't had my coffee yet or were irritated or something I'd probably just ask to talk to someone else.
That said, as I've explained elsewhere in the thread, the point isn't to see how many they know. It's to see that a) they know some portion of it that people doing the work would know, and b) have reactions to the rest that indicate useful work habits and attitudes.
A perfectly find first answer to is "I only use ps -aux. I'd just look in the man page if I needed anything else." Because then we could have a good discussion of how they use that output to figure out things, what sort of things they'd expect to see in the man page, and what other tools they use to see what's going on.
I know you're not asking people recite "ps" flags from memory. The problem is, you're looking for a subjective "X-factor" in how someone answers a trivia question.
I used to really like this approach too. I'd think of things that you'd only know if you'd actually done the kind of work I'd done. I had some favorite interview questions: "what are some of the functions you carry around with you from project to project in your 'libyou.a' library", and "where would you start looking if you had to debug a program that segfaulted in malloc"? I think the logic I was using is the same as the logic you're using here.
Ultimately, I think it's a bad approach. Equivalently strong candidates look at their work through different lenses, and find different things memorable. Far more important to me, though, is that some people really suck at interviewing --- and, what motivates me more, having succumbed to this repeatedly as a hiring manager and also being myself I think an example of the phenomenon --- some people just interview way better than they should.
The other problem with this question is that, by its phrasing, it implies that there is a right answer. If I can name more ps flags than an other person, I'm a better candidate. Which when put that way, I think points out its faults. Maybe you don't intend for that to be true, but you'd have to fight your own cognitive biases pretty hard to not at least bias towards the person that can name 17 flags off the top of their head, or the one that teaches you a new flag combo you didn't know. Even though those things are likely not that good of predictors of a good candidate.
You've said what you really want to get to, is can they admit when they don't know something. If that is important to your hiring process (and I'd encourage you to validate that with data), ask them a question no one could know the answer to. Ask the same question to every candidate, and grade it purely pass fail. Did they say "I don't know" or not.
>> admit when they don't know something... encourage you to validate that with data
My experience is that people that won't admit they don't know something are not necessarily bad employees. Often they are capable employees, although this is a trait I rarely see in the best employees. However, I find they are toxic to a good work environment, since they won't listen to people who do know something.
They do seem to get promoted to management had a much higher rate :)
/actually I'd probably hit up the man page first...
Since the 'ps -o' flags are only useful in that one command, I just look them up in the (rare) situation where they seem the best alternative. Having been at this for decades, I try to reserve my limited memory capacity for factoids that will pay off, and being able to process columnar data generically at an instant seems more useful than knowing a special way to do it with that one command.
Not sure how well this works in practice though.
They were. I was asked a ton of this kind of Linux/Unix trivia in one session. As well as just random stuff. For example:
https://twitter.com/ubernostrum/status/659182356171874304
So 1000 * 1000 * 16 = 16 million would be an easy estimate to make.
If you are designing a system and want to have an idea of how much space or memory an approach will take, being good at this kind of math can be really helpful.
(I mean, I get it, this kind of general estimation and/or ball-parking can be incredibly valuable, but this doesn't sound relevant in any way.)
To be fair to Google (in regard to this one filter question only), they actually are up front about expecting a significantly higher baseline of general mathematical awareness (even for non-mathy roles) than most other shops. At any rate, this kind of estimation comes up in capacity planning (both in architecture planning, and for algorithms on a single box) all the time. Which after all is what Google does, at nearly every level of their stack, (nearly) all the time.
So, no, still not useful questions.
As a result of having read this story, I can now always instantly remember what 2^24 is too :-).