Re: [PATCH] mv: add --swap (-s) option to atomically swap 2 paths

[Rob Landley]

On 3/1/24 05:05, Petr Malat wrote:
> Hi!
> On Fri, Mar 01, 2024 at 09:18:31AM +0000, Padraig Brady wrote:
>> On 29/02/2024 22:02, Petr Malat wrote:
>> > renameat2() syscall allows atomically swapping 2 paths on one
>> > file system. Expose this ability to the user using -s option.
>> > 
>> > * NEWS: Mention the new option
>> 
>> Thanks for the patch.
>> 
>> That was suggested previously:
>> https://lists.gnu.org/archive/html/coreutils/2021-05/msg00030.html
>> 
>> I agree this is useful functionality,
>> but the thinking is we should add this to a "replace" utility
>> rather than to mv.
> 
> I have modified mv, because for me it would be a logical place where
> to look for such a feature, and to make something usable, it must be
> easy to find.

I used "mv -x" for it, but if you have a strong preference for -s it hasn't been
in a release version yet.

I can submit a patch to busybox to add it there if we agree on a UI. (I will not
be adding a "replace" command to toybox: mv already replaces files and this is a
flag to the rename() system call that "mv" is already built around. This is an
atomic exchange, the new flag is RENAME_EXCHANGE, hence "-x" meaning exchange.)

Rob