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bug#14116: [PATCH] ln: allow to overwrite relative symlink
From: |
Pádraig Brady |
Subject: |
bug#14116: [PATCH] ln: allow to overwrite relative symlink |
Date: |
Tue, 02 Apr 2013 01:16:12 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 |
On 04/01/2013 09:10 PM, Rémy Lefevre wrote:
> Rémy.
>
>
> 2013/4/1 Pádraig Brady <address@hidden <mailto:address@hidden>>
>
> On 04/01/2013 03:40 PM, Rémy Lefevre wrote:
> > Overwriting relative symlink leads to undesirable behavior. Consider the
> > following example:
> >
> > # Create some directories
> > mkdir test
> > mkdir test/folder1
> > mkdir test/folder2
> >
> > #Create some files
> > touch test/folder1/file1
> > touch test/folder1/file2
> >
> > #Create a relative symlink in folder2 to file1
> > ln -sr test/folder1/file1 test/folder2/link
> >
> > #Check the link
> > ls -l test/folder2/link
> > # Correctly output a link to ../folder1/file1
> >
> > #Overwrite the symlink to point to file2
> > ln -sfr test/folder1/file2 test/folder2/link
> >
> > #Check the link
> > ls -l test/folder2/link
> > # Wrongly output a link to file2 instead of ../folder1/file2
> >
> >
> > This undesirable behavior is due to a dereferencing of the target when
> the
> > relative path is computed. Passing CAN_NOLINKS flag to
> > canonicalize_filename_mode solves the problem.
>
> Doing that though breaks `ln -sr target1 target2 dir` where dir is a
> symlink.
> Also if /some/other/component of the path is a symlink, you probably want
> that resolved? You might even want the final component of the link name
> resolved in some cases. So perhaps the approach here is to only disable
> dereferencing when -n is set, and even then only for the last_component()?
>
> In other words, `ln -nsf ...` means update the specified link name no
> matter what it is.
> -n used only be significant when the link name was to a directory,
> but with -r it's also significant if linking outside its containing
> directory.
>
> I'll sort out a patch later.
>
> You are right. It breaks any path composed of link. Sorry for this bad patch.
>
> But could you provide me an example where the final component of the link
> should be resolved ? Does it make sense as the link will be overwritten? I
> must be missing something.
Yes resolving the last component would be a departure from existing behavior.
So it there is no need to conditionalize this on -n, and we just need
to resolve the path without the last_component() and then tack that on.
thanks,
Pádraig.