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Comment by drfuchs | Hacker News Reader

A more direct (though fictional) illustration that Unix also has reserved file names that you'd better avoid: "I was writing a novel about digging to the center of the Earth, entitled "core". One day I was running some program that crashed, and my novel turned into a bunch of binary gibberish." Or how about: "My video of my kid's first at-bat, in a file I named a.out, got mysteriously clobbered when I took my first programming class." These are more insidious than the MSDOS examples, which at least fail right away.

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They are less insidious by far. You're really reaching for threads here.

The first, `core`, isn't relevant. `/proc/sys/kernel/core_pattern` configures that value, and by default it's named "core.$PID" nowadays.

That's far better than windows' wart since it's configurable, disableable, etc.

Your second example is even more contrived. If you run a tool which writes files, of course it can overwrite files. I don't complain that in windows when I type "copy foo bar" my "bar" file is overwritten by "foo".

In the same way, someone who voluntarily runs "gcc x.c" or "cat > foo" should not be surprised when "a.out" and "foo" respectively are overwritten.

There's a massive difference between an unconfigurable gotcha based on a filename and an explicit action which writes a file.

If you'd like a real world example, I once used the predictably of core dump filenames to (legitimately) gain root access to a busy public nameserver.

https://inopinatus.org/2015/08/24/privilege-escalation/ has the detail.

(^predictability)

>My video of my kid's first at-bat, in a file I named a.out, got mysteriously clobbered when I took my first programming class.

This is a failure to understand GCC's default behavior, not a fundamental flaw with your operating system.

The "core" thing is a little more understandable, but it can all be remedied by choosing reasonable filenames with accurate file extensions. "aux.c" isn't that unreasonable, and if I'm reading it right, he could've called it "aux.foo" and it still would've been broken.

> This is a failure to understand [Program X]'s default behavior, not a fundamental flaw with your operating system.

Ah, yes, the age old Unix trope of, "it's not the system, it's the user's fault".

As a Linux user for many years, that doesn't excuse such boneheaded errors. By default no application should clobber existing files, unless asked to. Avoid data loss and all that.

Heck, I remember back when:

tar myfile.txt myarchive.tar

would result in myfile.txt being truncated to 0 bytes (therefore deleting its contents) and a snarky message that myarchive.tar can't be archived because it can't be found.

For those that don't remember how tar works, the arguments are reversed compared to, say, cp.

At least I think they've fixed it, newer tar version says something like "Cowardly refusing to create an empty archive".

The Unix ecosystem, dragged kicking and screaming towards user-friendliness since 1970.

>Ah, yes, the age old Unix trope of, "it's not the system, it's the user's fault".

Well, if the user had read the manual before using GCC, it wouldn't have happened.

Regardless, I don't blame them or look down my nose at them. It's bad design. If it's anyone's fault, it's GCC's. But it's certainly not a problem with Unix. This makes it incomparable to the system-level issue of having global filenames like DOS did, apparently.

Well, as far as modern design goes, I doubt many people argue that Unix was better designed than DOS. DOS was a single user, single tasking OS meant for very limited hardware.

While Unix was kind of Ok, when coupled with its common userland utilities, the whole often felt like a cactus. Possibly useful, if you don't mind the scars :D

I'm a professional software developer (well, "professional"; I have a part time programmming job next to studies), where I program in C++, compiling with GCC. I have never read GCC's manual. Expecting newcomers to read the 18 thousand lines of man page before trying to make a program isn't reasonable.

Of course, the man page is a great resource for looking things up, but I can't imagine many people sit down with GCC's man page and actually read it through.

> Ah, yes, the age old Unix trope of, "it's not the system, it's the user's fault"

Except that example could also happen on Windows.

Looks like it is time for this again...

> Ah, yes, the age old Unix trope of, "it's not the system, it's the user's fault"

Ah, yes, the age-old complaint that a car driver should be able to run a forklift with no practice.

I don't think Unixen should strive for 'user friendliness'. Hacking in "Do you really want to" dialogs would (a) be contrary to all expectations developed over a long time, (b) break a lot of existing software, (b) annoy the bloody hell out of everyone, and (d) not solve anything, because those dialogs don't prevent mistakes.

Not all systems need to converge, and Unix has been a professional toolchain since the beginning. You're expected to know something about it, just like you don't let kids run plasma cutters.

"My video of my kid's first at-bat, on a DVD in front of my plasma cutter, got mysteriously clobbered when I turned the cutter on."

  > For those that don't remember how tar works, the arguments are reversed compared to, say, cp.

Tar doesn't have positional file arguments; you use the 'f' flag to specify an archive file. You might be thinking of zip or some similar archiver in the DOS heritage.

My bad, I was actually talking about a very common tar idiom which is almost an automatism for me:

tar cvf/czvf/cjvf archive files (or -cvf/-czvf/-cjvf).

I don't think I've ever seen anyone actually using tar by going:

tar -c files -f archive

Online tutorials seem to also use my form: http://www.thegeekstuff.com/2010/04/unix-tar-command-example...

Either way, bad form, I'm glad they fixed it :)

If we're going to criticise Unix file naming, I'd rather talk about how file names with spaces in them break things, or how hard it is do delete a file named "-".

There's something in my environment that keeps creating a file called "-" in my home directory, and it's driving me crazy.

By convention, when a unix program is passed "--" it means there are no more flags being passed. Try the following:

$ rm -- -

This will not work with all rm implementations, in which case you can fall back to: rm ./-

Oh, I can remove it... And a few hours or days later it's back!

Okay, you're gonna want to type $sudo crontab -e...

It is better to write EDITOR=nano sudo crontab ... otherwise instead of edititng the crontab you will be solving the problem of exiting vi.

All the interest encouraged me to dig in and find it, and it turned out to be in one of zsh's many startup scripts.

list the file showing inode number, rm by that particular inode.

Open the parent directory with emacs and you can use it to delete the rogue directory/file. Admittedly, there's easier ways for a "-" named file, but its a good solution to know since you can use it to delete even the most difficult filenames.

  rm -- -

While GNU's not unix... afaik GNU coreutils' rm has done exactly what you expect it to when given a single dash as an argument for who knows how long.

The problem is names that could be interpreted like options, like '-f' or '--help'.

Interestingly, when the shell expands * , it won't do anything to make sure files starting with - are handled properly.

This means, if you're in a directory with the files a, b, -rf, and the directories foo/ and bar/, running "rm * " will not delete all the files and keep all the directories; instead it will be turned into "rm a b bar foo -rf", meaning it will delete all the files and directories except for the file -rf.

I've definitely run into this on bash and zsh (iirc). I'm curious if this glob expansion behaviour is set in posix somewhere.

You don't really put videos into a program's source tree. Also I don't think any modern Unix-like OS would overweite a file with a core dump no matter what is the name, and doubt that ancient versions did so too. Having the same set of device files under every directory is quite a different thing.

Actually, not only did they do exactly that, they could even be induced to do so through a symlimk, with hilarious results.

I'm really curious about them hilarious results now :)

Actually, when I just want to test something silly, I often just go to ~, make a file test.c or something, write the short test program, and run `gcc -o test test.c`. It's not that rare to have videos in your home directory, and if I had one named a.out, and forgot the -o option, it'd get overwritten.

Not saying it's remotely likely, just saying that having video files in a program's source tree isn't the only way it could happen :)

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