Re: copy-file: ok-if-already-exists versus mustbenew

[Luc Teirlinck <teirllm@dms.auburn.edu>]

Lennart Borgman wrote:

   I am trying to enhance my reading capabilities, but I can not understand 
   the difference between the arguments ok-if-already-exists and mustbenew 
   in the doc for `copy-file'. Can someone please explain this to me?

   The only difference I see is that  "never overwrite" is mentioned for 
   "mustbenew" - though I hope this holds for the first argument too.

I do not immediately see the difference either.  mustbenew was
introduced by the following change:

2005-04-23  Richard M. Stallman  <rms@gnu.org>

	    * fileio.c (Fcopy_file): New arg MUSTBENEW.
	    (Frename_file): Pass new arg to Fcopy_file.

I do not immediately understand why Frename_file could not have used
the ok-if-already-exists arg.

   However it sounds like the second argument should be about modification
   times, but the doc string does not say so.

I do not understand this one.  I assume you mean the second _optional_
argument.  From the docstring:

   Fourth arg keep-time non-nil means give the output file the same
   last-modified time as the old one.  (This works on only some systems.)

Another problem is that the preserve-uid-gid arg is not mentioned in
the `(elisp)Changing Files' description of copy-file.

Sincerely,

Luc.