I'll bite

Post #17,532 by broomberg 11/9/01 2:39:48 PM Reply	I'll bite Attempt to create a file called '/tmp/wicked\\n/etc/passwd' By why? It fails because the '/' after the '\\n' signifies another dir level that does not exists. I assume it is an attempt to leave some type of trap for the passwd program, but it escapes me. Note: I got 2 wrong. Umask and something else. I always hated umask.
Post #17,542 by ben_tilly 11/9/01 3:06:03 PM Reply	So far so good, now for a hint First of all they got the umask question wrong, and the answer is distro dependent. (Also anyone sane writes a umask with at least 3 digits, not 2.) But back to the interview question. You are perfectly right about what the command does. So, assuming that the previous two levels of directories were previously created (say in the previous two lines) and the desired file was created, what is the point? At this stage in an interview I would give a hint. The hint is to think about cron jobs which are likely to exist. Cheers, Ben
Post #17,552 by Steven A S 11/9/01 3:58:13 PM Reply	My guess Is there a program that is usually set up to clean up the /tmp folder? If such a program were to access a directory of the /tmp dir would it not see that one mangled filename as two separate files (the newline separating them)? Would it not then in deleting the file end up deleting both? BTW I missed 7 on those, and a few of those I shouldn't have. Doh! ~~~)-Steven---- "I want you to remember that no bastard ever won a war by dying for his country. He won it by making the other poor dumb bastard die for his country..." General George S. Patton
Post #17,568 by ben_tilly 11/9/01 4:43:17 PM Reply	Bingo If said cron was written as a shell script using find to produce a list of files to remove, and then removing them, it would be very easy to make exactly that mistake. And, of course, that would have to run as root, so it is able to blow away your password file. If you wrote it in C, Perl, or any other "real programming language", you would not confuse returns inside of filenames as breaks between filenames. Cheers, Ben
Post #17,655 by cforde 11/10/01 1:05:58 AM Reply	gak a linefeed character in a file name? Ok, what characters aren't allowed in a Unix file name? Have fun, Carl Forde
Post #17,683 by ben_tilly 11/10/01 2:14:08 PM 11/10/01 2:15:31 PM Reply	null and / Insert usual fun and games with backspace characters, characters which cause X to do funky things, etc. Edited by ben_tilly Nov. 10, 2001, 02:15:31 PM EST Expand All History
Post #17,723 by boxley 11/10/01 10:44:44 PM Reply	dont forget pipe and redir \| > and your example would be ok inside " as opposed to `(maybe) thanx, bill tshirt front "born to die before I get old" thshirt back "fscked another one didnja?"
Post #17,829 by ben_tilly 11/12/01 4:59:39 AM Reply	touch 'foo \| bar > baz' Works perfectly well for me. Cheers, Ben
Post #17,823 by cforde 11/12/01 1:12:27 AM Reply	Berkeley, Unix and something else I'm reminded of a quote about Berkeley, Unix and something else. I'm sure you know what it is... What is the point of allowing control characters? I assume the ommission of null is an artifact of C strings? [link\|http://www.linuxdoc.org/HOWTO/Unicode-HOWTO-3.html\|Unicode filenames] are cool though. Have fun, Carl Forde
Post #17,830 by ben_tilly 11/12/01 5:02:10 AM Reply	It is easier to allow than to disallow Null and the / already were taken. They had assigned meanings, one for C and the other for directories. Any other characters which you wanted to disallow would be more work. So they just allowed them all. Cheers, Ben

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