linux-kernel - Re: UNIX Compatibility

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Date:	Thu, 26 May 2011 08:07:59 -0400
From:	Valdis.Kletnieks@...edu
To:	Bernd Petrovitsch <bernd@...rovitsch.priv.at>
Cc:	Michael Witten <mfwitten@...il.com>, "Ted Ts'o" <tytso@....edu>,
	Mike Galbraith <efault@....de>,
	Richard Yao <ryao@...sunysb.edu>, linux-kernel@...r.kernel.org
Subject: Re: UNIX Compatibility

On Thu, 26 May 2011 13:30:39 +0200, Bernd Petrovitsch said:

> Or take the "unlink a directory gives EPERM" example: why is it
> specified with an errno that indicates that the user is not allowed to
> remove it (and not that the sys-call is the wrong one).

Because on some old Unix's, it wasn't the wrong syscall...

RATIONALE

Unlinking a directory is restricted to the superuser in many historical
implementations for reasons given in link() (see also rename()).

http://pubs.opengroup.org/onlinepubs/009695399/functions/unlink.html

I've encountered at least one system (admittedly 20+ years ago), where
unlink("./") actually did work. Took me a while to correlate the weird fsck's
at reboots to the program that tried to remove './$A' when $A was unset...

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