Re: Unix * weirdness

[ysyi () TACO ASYNC ORG (Yong S. Yi)]

Blue Boar stuffed this in my mailbox Today (01/01/00) at 2:04pm:
> This is one of those funny thing I notice when doing my regular job.
>
> # rm -R *
> rm: illegal option -- p
> rm: illegal option -- o
> rm: illegal option -- c
> usage: rm [-fiRr] file ...
>
> It took me a minute.  It's taking the file named -proc and parsing as if
> it was a set of command line options.  I guess this makes some sense.. I
> believe the shell just takes all the files and makes them all
> command-line parameters when you use *.

Right, that's shell expansion for wildcards.

> BTW, I got rid of it with:
>
> # unlink -proc

Try something like "rm ./-proc", "rm -- -proc", etc.

> So, I wonder what other kinds of traps can be laid for the root user or
> cron jobs, etc...  For example, here's a line from my S05RMTMPFILES in
> /etc/rc2.d dir, on a Solaris 2.6 machine. (Which is where this behavior
> was noticed):
>
> /usr/bin/rm -rf /tmp/*

Nothing. Well, the files will get unlinked, but that's about all. That's
matching (for example) "/tmp/-proc", not chdir()'ing into /tmp then
running "rm -proc" (unlink()).

> So, if I can place an interestingly names file in /tmp (and anyone can)
> can I get interesting things to happen when the machine reboots.

Not really; I'm sure if you worked out some buffer overflow with 'rm' yada
yada (remember the bash PS1 deal?)...

> For example, can I get a file with spaces in it?  How about the |
> (vertical bar) character?  How about a ; ?

Yes, you can create files with spaces in it, with |'s in it, and ;'s.

Like, uh:

% pwd
/tmp/lame
% ls -l
-rw-------   1 ysyi     ysyi            0 Jan  1 17:19 -asdf
-rw-------   1 ysyi     ysyi            0 Jan  1 17:19 as
-rw-------   1 ysyi     ysyi            0 Jan  1 17:19 asd sdk
-rw-------   1 ysyi     ysyi            0 Jan  1 17:19 asf;fj
-rw-------   1 ysyi     ysyi            0 Jan  1 17:19 dfklj
% rm -rf /tmp/lame/*
% ls
%

> (Yes, I could test it myself if I had time at the moment.)

You didn't have time to test *that*, yet you had time to write this
e-mail?

> Is this a really old "feature" that everyone knows about except me?

No feature about it -- it's just shell expansion, and the issue being more
of a system administration thing than much else.

-y.

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Yong S. Yi          KeyID 1024/8B4FF151        http://async.org/~ysyi/
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