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

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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: Mon, 04 Nov 2013 01:48:11 +0100

On 11/02/2013 01:07 AM, Pádraig Brady wrote:
> So I would be 60:40 for going with Gian's addition
> of dereferencing with just `cp -l`, and I would be
> 60:40 against changing the behavior of `ln` even though
> it would now be inconsistent with `cp -l` (and still inconsistent with BSD).

Thanks for the summary.

After playing a bit more, I'd also tend to use Gian's solution:
hard links to symbolic links are probably not that useful, because
* they have the same owner/group as the original symbolic link which
  could lead to problems with permissions during removal of the symlink
  in a sticky dir like /tmp), and
* the target cannot be changed without creating the symlink again
  which is problematic to remember in both places.

BUT I'm not happy at all with the following case:

  $ : > file
  $ ln -s file filelink
  $ src/cp --link filelink dst--link
  $ src/cp --link -R filelink dst--link-R
  $ ls -ldogi file filelink dst--link dst--link-R
  537364 -rw-r--r-- 2 0 Nov  4 01:30 dst--link
  537365 lrwxrwxrwx 2 4 Nov  4 01:30 dst--link-R -> file
  537364 -rw-r--r-- 2 0 Nov  4 01:30 file
  537365 lrwxrwxrwx 2 4 Nov  4 01:30 filelink -> file

That's exactly what Gian was worried about in a different case
of my solution: it *matters* whether the rather unrelated -R option
is specified or not. ;-(

It got late again. I'll have a look tomorrow again - maybe there
are no side effects with the following:

diff --git a/src/cp.c b/src/cp.c
index 7bc8630..78c0a04 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -1135,7 +1135,7 @@ main (int argc, char **argv)

   if (x.dereference == DEREF_UNDEFINED)
     {
-      if (x.recursive)
+      if (x.recursive && ! x.hard_link)
         /* This is compatible with FreeBSD.  */
         x.dereference = DEREF_NEVER;
       else

Have a nice day,
Berny

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