Re: chmod changing ctime even if no mode change

[Ray Dillinger]

On 10/13/2013 05:43 AM, Bernhard Voelker wrote:

> I'm somehow tempted to read that as "but don't do it if nothing has
> changed". Fixing the code accordingly wouldn't be too hard ... _but_
> that would stand in contrast to commit f8e66794 [3] which (probably
> precautionarily?) did it the other way round back in 2000:
> 
>   Perform the chmod even if the
>   file mode permission bits are the same as those that should be set.
>   Omitting the chmod call would be alright with minimal 1003.1e DS17
>   ACLs, but eventually there will be other permissions in addition to
>   rwx.  E.g., add and delete for directories, and something analogous
>   to NT's take ownership permission.
> 
> Does anyone know of a real situation where omitting the actual chmod(3)
> call would cause problems?  Otherwise, I'd say that current chmod(1)
> violates POSIX.

> WDYT?

My opinion is that chmod should definitely update the file time if it
changes any permission or file attribute, and that on systems that
have permissions beyond rwx, or more than 3 'levels' of permissions,
that includes cases in which the changes did not include any of
the classic UNIX permission bits.

Conversely, if it changed _nothing_ about the file's permissions or
attributes, then it ought not update the timestamp either.

                                Bear