GNU bug report logs - #15173
[cp] --link overrides dereference settings

Previous Next

Full log

View this message in rfc822 format

From: Bernhard Voelker <mail <at> bernhard-voelker.de>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: Gian Piero Carrubba <gpiero <at> rm-rf.it>, Eric Blake <eblake <at> redhat.com>, 15173 <at> debbugs.gnu.org
Subject: bug#15173: [cp] --link overrides dereference settings
Date: Thu, 31 Oct 2013 14:17:24 +0100 (CET)

> On October 31, 2013 at 1:12 PM Pádraig Brady <P <at> draigBrady.com> wrote:
> That all seems consistent with expectations and what we previously discussed.
>
> But...
>
> I've just now read POSIX for cp, and it states:
>
>  "If the -R option was not specified, cp shall take actions based on the type
>   and contents of the file referenced by the symbolic link, and not by the
>   symbolic link itself, unless the -P option was specified."
>
> This suggests that -HL should only be significant with -R ?
> That is a bit surprising TBH. What do you think Eric?
>
> It also suggests that we should hardlink to a symlink only with -P,
> i.e. that we should AT_SYMLINK_FOLLOW unless -P is specified ?
> That's also a bit surprising, given that POSIX for ln states
> that it's implementation defined what's done if neither -P or -L is specified.
> I wouldn't be inclined to follow POSIX in that regard.

I don't read the POSIX spec that way: there are 2 things to consider:
a) POSIX doesn't say a word about hard links, and
b) the -l,--link option is a GNU extension to conveniently
   copy files or trees by creating hard links (only).

I.e. if someone uses -l, then the POSIX semantics does not
apply anymore because we do not copy anymore.  Whether the
ln(1) specification does apply more here is another question.

Therefore, I think GNU cp(1) should do what makes most sense
for the user - depending on -LPH or none being used.  With the
proposed patch, I think we're getting a bit closer to that.

Have a nice day,
Berny

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.