Re: File copy system call proposal

[Jamie Lokier]

Daniel Phillips wrote:
> > > Consider the _very_ common case (that nobody has mentioned yet) where you
> > > are editing a large file.  When you write to the file, the editor copies
> > > the file to a backup, then immediately truncates the original file and
> > > writes the new data there.  What would be _far_ preferrable is to
> > > just
> > 
> > Are you sure? I think editor just _moves_ original to backup.
> 
> It would be so nice if all editors did that, but most don't according to the 
> tests I've done, especially the newer ones like kedit, gnome-edit etc.  I 
> think this is largely due to developers not knowing why it's good to do it 
> this way.

Moving the original to make a backup is a _bad_ thing if the original
might be hard-linked and you'd like all instances to be written to.
OTOH it'a a good thing if you're using hard links for poor man's version
control (`cp -rl').  Hey :)

Emacs does this perfectly with `backup-by-copying-when-linked' (an
option you can change, but I like it on).

-- Jamie