busybox cp vs gnu cp

[Denys Vlasenko]

On Tuesday 16 September 2008 03:49, Ming-Ching Tiew wrote:
> 
> Tried this with busybox :-
> 
>    # cp /etc/hosts /tmp/a
>    # ln -s /tmp/a /tmp/b
>    # cp /etc/passwd /tmp/b
> 
> After this, /tmp/b which was a symbolic link has become a normal 
> text file which content is /etc/passwd. File /tmp/a 
> remaind unchanged.
> 
> When I tried this with gnu 'cp' the end result
> is /tmp/b remain as a symbolic link, and /tmp/a was modified
> accordingly.

This is intended. Coreutils cp behavior is dangerous.
Just imagine that the user running this command wants this:

"copy /etc/hosts to /tmp/a, creating /tmp/a if it doesn't exist,
or overwrite if it exists. In other words, I don't care
whether it exists or not, I simpy want to make an exact
duplicate of /etc/hosts."

which is what English word "copy" implies, right?

If you really want "overwrite symlink destination" semantic,
why won't you do "cat /etc/hosts >/tmp/b"?
In such command, your intention would be much clearer.

--
vda