Re: symlinks and targets are not the same file

[Eric Blake]

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According to Karl Berry on 12/4/2009 6:51 PM:
> [coreutils 8.1, gnu/linux]
> 
> $ touch foo 
> $ ln -s foo lnk
> $ \cp --no-dereference foo lnk
> cp: `foo' and `lnk' are the same file
> 
> Well, no, they're not.
> I expected the file foo to overwrite the symlink lnk.
> I can imagine that error without --no-dereference, but with it ... ?

I'm not so sure it is a bug.  cp --help | grep no-deref states:

  -d                           same as --no-dereference --preserve=links
  -P, --no-dereference         never follow symbolic links in SOURCE

But lnk is a DEST, not a SOURCE.  Which means you effectively did 'cp foo
foo'.

On the other hand, not even -T/--no-target-directory is enough to make us
try to blindly overwrite lnk, rather than stat()ing through it.  And it
almost seems like 'cp --no-deref -f foo lnk' should recognize failure to
copy, perform the unlink(), and try again, thus succeeding to overwrite
lnk with a regular file.  So, I'm fuzzy on whether you found an actual bug.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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