The long interview day is nearing its end. Googamazbook got the best and the worst out of you (well, neither of those, but I’m trying to put some literature in here); the last interviewer comes in, smiles condescendently and greets you with:
Time for the easy interview, heh?
Yes, you have all the reasons to be concerned and feel you’re just one step away from failure (yes, why didn’t you spend the day by the pool in the basement of the many stars hotel they got you a room in for the interview?). But without further ado, the questions start pouring in:
Question 1
How do you figure out if a process is CPU bound or I/O bound?
Tricky! Let’s not jump to the conclusion. There are 2 variables here, this means we have 4 possibilities:
Note: The first 3 episodes of the interview series can be found here, here and here.
Question 1:
You have the shared document open and the phone rings. The interviewer, at the other end of the line, starts with a thick accent:
– What does ls * do?
You cannot believe your ears: it sounds easy. Really easy. So you answer in the line of “it lists all the files in the current directory”. The interviewer follows up with one or 2 questions on how it really works and you answer about the star being passed as a parameter to ls and how the binary interprets it in some way that it gets the entire directory walked over and its contents listed. Simple!
Note: this text is about Systems Programming on Linux platforms.
This type of interview is focused on finding out what do you know about what happens below the “command line” surface. Down there things can get messier, as processes get created, terminated, the output gets collected, system calls are performed. Things get complicated really fast for the unaware or the unprepared.
Let’s take for example a single command that is being run:
$ ls
This is a classical interview question, asked for more than 15 years now. I’m not sure if anyone still asks it in 2016, but it’s still interesting to see the answer. So, what happens when this is being run? (No, not the file list display).
From the beginning: