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:
Note: The first 2 episodes of the interview series can be found here and here.
Question 1:
The interviewer comes in and hands you the following ls -la listing:
# ls -la total 108 dr-xr-x---. 7 root root 4096 Sep 5 07:16 . dr-xr-xr-x. 22 root root 4096 Sep 1 17:43 .. -rw-------. 1 root root 15432 Sep 5 06:36 .bash_history -rw-r--r--. 1 root root 18 May 20 2009 .bash_logout -rw-r--r--. 1 root root 176 May 20 2009 .bash_profile -rw-r--r--. 1 root root 176 Sep 23 2004 .bashrc -rw-r--r-- 1 root root 0 Sep 5 07:16 -f ...
They say the -f file must go; would you please delete it?