Rename file without overwriting existing files

[Grant Edwards]

On 2017-01-30, Jussi Piitulainen <jussi.piitulainen at helsinki.fi> wrote:

> It doesn't seem to be documented. I looked at help(os.link) on Python
> 3.4 and the corresponding current library documentation on the web. I
> saw no mention of what happens when dst exists already.

The functions in the os module are thin-as-possible wrappers around
the OS's libc functions.  The authors of the os module don't really
have any way of knowing the details of what your os/libc combination
is going to do.

If you're calling os.foo(), you're sort of expected to know what foo()
does on your OS.

> Also, creating a hard link doesn't seem to work between different file
> systems, which may well be relevant to Steve's case. I get:
>
>     OSError: [Errno 18] Invalid cross-device link: [snip]
>
> And that also is not mentioned in the docs.

Again, that's a detail that depends on your particular
OS/libc/filesystem implementation.  It's not determined by nor
knowable by the authors of the os module.

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