GNU bug report logs - #8850
mkdir inside symlink creates wrong directory with relative parent

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Oldřich Jedlička <oldium.pro <at> seznam.cz>
To: bug-coreutils <at> gnu.org
Subject: mkdir inside symlink creates wrong directory with relative parent
Date: Mon, 13 Jun 2011 12:50:19 +0200

Hi all,

I was trying to search for any description helping me understand in
what I see, but actually I didn't find any, so I'm here. I discovered
it by using automake-1.11, because it uses relative paths a lot. So my
simplified testcase is as follows:

Have a directory structure x/y and x/z/a. Have a symbolic link from
x/y/z that points to x/z.

 mkdir -p x/y
 mkdir -p x/z/a
 ln -s ../z x/y/z

Now go into x/y/z/a and try to create directory like that:

 cd x/y/z/a
 mkdir ../dir_xyz
 mkdir ../../dir_xy
 mkdir ../../../dir_x

I would expet that there would be a directory like this:

 x/dir_x
 x/y/dir_xy
 x/y/z/dir_xyz (x/z/dir_xyz)

But the result is completely different:

 dir_x
 x/dir_xy
 x/y/z/dir_xyz (x/z/dir_xyz)

So when you want to create a directory in the parent structure from
within the symbolic link, you will fail in doing so, because the
symbolic link would be resolved during walking through parents, so you
can get to completely different tree while creating your directory. It
looks like a bug, because it is nowhere documented to behave like that
(and the behaviour is strange by itself).

Verified on Debian 4.0/RedHat 5.4 with coreutils 5.97 and on Gentoo
with coreutils 8.12.

Regards,
Oldrich.

Message #10 received at 8850-done <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Oldřich Jedlička <oldium.pro <at> seznam.cz>
Cc: 8850-done <at> debbugs.gnu.org
Subject: Re: bug#8850: mkdir inside symlink creates wrong directory with
	relative parent
Date: Mon, 13 Jun 2011 16:55:32 +0200

Oldřich Jedlička wrote:
> I was trying to search for any description helping me understand in
> what I see, but actually I didn't find any, so I'm here. I discovered
> it by using automake-1.11, because it uses relative paths a lot. So my
> simplified testcase is as follows:
>
> Have a directory structure x/y and x/z/a. Have a symbolic link from
> x/y/z that points to x/z.
>
>  mkdir -p x/y
>  mkdir -p x/z/a
>  ln -s ../z x/y/z
>
> Now go into x/y/z/a and try to create directory like that:
>
>  cd x/y/z/a
>  mkdir ../dir_xyz
>  mkdir ../../dir_xy
>  mkdir ../../../dir_x
>
> I would expet that there would be a directory like this:
>
>  x/dir_x
>  x/y/dir_xy
>  x/y/z/dir_xyz (x/z/dir_xyz)
>
> But the result is completely different:
>
>  dir_x
>  x/dir_xy
>  x/y/z/dir_xyz (x/z/dir_xyz)
>
> So when you want to create a directory in the parent structure from
> within the symbolic link, you will fail in doing so, because the
> symbolic link would be resolved during walking through parents, so you
> can get to completely different tree while creating your directory. It
> looks like a bug, because it is nowhere documented to behave like that
> (and the behaviour is strange by itself).
>
> Verified on Debian 4.0/RedHat 5.4 with coreutils 5.97 and on Gentoo
> with coreutils 8.12.

Loic explained that this is not a bug. (Thanks, Loic.)
I'm marking this issue as closed.

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