Stupid Interview Questions · 10 March 2010

I was reading a blog post on some guy’s programming interview, where he complained about being asked to write a file copy function. Now, while it’s quite possible to take umbrage at this, if I were in that situation, I’d see it as a chance for some free entertainment .

Q. What do you mean by “copy”?
A. Ummm…copy the contents of the file to a new file.
Q. What about the date/time stamps?
A. No, those don’t need to be copied.
Q. Does the result file have to have the same name?
A. No.
Q. Can it have the same name?
A. Umm…no.
Q. Do I have to worry about name spoofing? What about the Turkish I?
A. Don’t worry about that.
Q. Does it have to be in the same location? Note that if it is in the same location, it (probably) can’t have the same name. Unless you copy it to itself (another question…).
A. Yes.
Q. What about the attributes?
A. Make the attributes the same.
Q. Should I modify the attributes of the source file? If this file copy is part of a backup or archive operation, it’d probably be a mistake to leave the ‘Archive’ attribute on.
A. No, leave them as-is.
Q. What if the source file has the Archive attribute off? If I make it off on the new file as well, it could screw up the user’s backup software.
A. Just make it the same. I don’t care about the user’s backup software.
Q. Well, I’m not sure that’s the best approach to take when thinking about designing software FOR users, but if you say so.
A. …
Q. What about compression? It’s a file attribute, but the copy destination may not support compression.
A. Don’t compress the copy.
Q. Even if the source is compressed, and the destination supports compression?
A. YES.
Q. What about encryption? What if the source file is encrypted, but the destination does not support encryption?
A. Don’t encrypt the copy if the destination doesn’t support it.
Q. Mmmmm, sorry, don’t mean to digress, but…that could be a serious security hole. Especially if wherever this file copy function ends up supports arbitrary parameters (directly or indirectly).
A. Look, just copy the damn file.
Q. What about the file creator?
A. Don’t care.
Q. What about the file owner?
A. Don’t care.
Q. What about file permissions? Is there a separate way we should handle inherited permissions and assigned permissions?
A. Forget the permissions.
Q. What operating system will this function be required to run on?
A. Windows XP.
Q. Home, or Pro, or Media Center, or one or more?
A. Pro.
Q. What service pack level are we aiming for?
A. Service Pack 2.
Q. Does that mean we don’t have to support any other SP level?
A. Yes, fine.
Q. How will the source file name be supplied?
A. As a parameter.
Q. Is it going to be supplied as a null-terminated string, a counted string, or an object?
A. Null-terminated string.
Q. Is it possible that a NULL pointer will be passed in?
A. No.
Q. Is it possible that an empty string will be passed in?
A. No.
Q. Is it possible that a malformed string will be passed in (e.g., no NULL terminator)?
A. No.
Q. What encoding will the filename be in?
A. Unicode.
Q. Sorry, umm…Unicode is not an encoding, really. If we’re using Unicode data, it has to have a specific encoding, like UTF-8, UCS-2, UTF-16, etc.
A. Fine. Make it UTF-8.
Q. OK. I’d like to note at this point that it’s a bit of a pain to have to transcode UTF-8 to UTF-16 in order to be able to supply it to Windows API calls.
A. Fine! UTF-16!
Q. Big-endian or little-endian?
A. ARGH. Whichever you want!
Q. Should we accept relative paths, or only fully-specified paths?
A. Only full paths.
Q. Are there any characteristics of the paths we are supposed to accept that I can screen the parameters on?
A. No. The caller will do all screening of paths and file names.
Q. How will the destination file name be generated or supplied?
…
Q. Am I required to support (or allow) an asynchronous copy operation?
A. No.
Q. How should I report errors? Exceptions? Error codes?
A. Whatever.
Q. Should I try and handle exceptions from called functions internally, or let them pass through to the caller?
A. Err…let them pass through.
Q. What if the destination file already exists?
A. It won’t.
Q. So the caller ensures that?
A. Right, sure.
Q. So if it does exist, I can just terminate the program, then? Obviously this would be a violation of preconditions, and who knows WHAT is going on.
A. Sure, whatever you want.
Q. What about alternate data streams?
A. Do whatever you want!
Q. Look, I’m sorry if you feel put-upon here, please don’t get hostile. I’m just trying to get a clear picture of the specs I need here. Obviously if I’m going to write a file copy method, instead of using one of the many extant file copy routines in various libraries and frameworks, it’s going to be fulfilling a specialized set of requirements, and I’m going to need to have good answers for these questions. If you want, I can hack something together in a minute, but I’d have to note that there were many unresolved issues as to requirements and purposes.
A. AIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Mission accomplished.

Edit: A software developer and blogger in Japan (Yasushi Aoki) generously offered to translate this article into Japanese. Thanks to his effort, you can now find Stupid Interview Questions — Japanese translation on his website.
日本語版はこちら

-- David --

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Poem: "London Trees" · 15 December 2009

I signed up for NaNoWriMo again this year — my third time — and as before, I did not finish. However, this is the first time I felt that I quit for a good reason. I had a plot outline constructed, and characters, and scenes, and my writing was clicking along quite well (averaging about 2000 words/hour, give or take). A few days into the month, though, I realized something: the writing of my novel had transformed from an exercise in writing the novel itself into an exercise in writing — in terrific detail — about all of the art I would rather have been doing instead of writing. I decided that it would be a much more productive, not to mention enjoyable, use of my time to actually just do the art I was really wanting to do, instead of writing about the doing of that art.
Anyway, the title of the novel I had started working on, “For Our Own Destruction Weep,” was taken from a poem by Kathleen Raine. Here is that poem (you can find it, along with many other excellent works, in Kathleen Raine’s Collected Poems, available at Amazon and other sources).

London Trees

Out of the roads of London springs the forest,
Over and underworld, the veritable Eden
Here we have planted for our solitude,
Those planes, where thoughts unblamed among the leaves may run.

Sensing us, the trees tremble in their sleep,
The living leaves recoil before our fires.
Baring to us war-charred and broken branches,
And seeing theirs, we for our own destruction weep.

And women, sore at heart, trying to pray
Unravel the young buds with anxious fingers
Searching for God, who has gone far away,
Yet still at evening in the green world lingers.

Obedient still the toiling trees
Lift up their fountains, where still waters rise
Upwards into life, filled from the surrounding skies
To quench the sorrows thirsting in the world’s eyes.

-- David --

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Survey: Are you House or Wilson? [Survey ended] · 28 October 2009

Survey’s over! The most popular choice was…well, see for yourself:

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