Re: [bug #51069] find changes access time on directories

[James Youngman]

On Sun, May 21, 2017 at 6:19 AM, Adesh Kumar <address@hidden> wrote:

> Thanks James Youngman for excellent clarification.
>
>
> I thought "find" uses only stat syscalls, but yeah I can see how that
> cannot help with directory contents. My guess is that for simple tests
> like iname or name, find does not need to read the direcotry list. Is my
> understanding correct?
>

Each directory itself  contains all the names of its children, and they
cannot be enumerated without reading the directory.    This means that your
understanding isn't correct.   See for example
http://www.grymoire.com/Unix/Inodes.html for further information.



> So, what are the filters, other than amin, mmin and the like, for which
> find needs to read the directory contents.
>

Find always reads the directory contents, that's how it searches the file
system.   There is no other way to do it.


> Can you please also explain this for me.
>
>
> Regards,
>
> Adesh
>
> ------------------------------
> *From:* James Youngman <address@hidden>
> *Sent:* 20 May 2017 18:02:16
> *To:* James Youngman; address@hidden; address@hidden
> *Subject:* [bug #51069] find changes access time on directories
>
> Update of bug #51069 (project findutils):
>
>              Assigned to:                    None =>
> jay
>
>     _______________________________________________________
>
> Follow-up Comment #1:
>
> The access time of the directory is being updated by the kernel when find
> reads the directory to search it.  POSIX requires this.
>
> If find offered an extension which saved and restored the st_atime in
> directories, then the step of restoring the st_actime timestamp would
> (unavoidably, I believe, because of the way utimes is specified) update the
> st_ctime timestamp.   That is, if anything, worse.
>
> If you want access times not to be updated, your best bet is to mount the
> file
> system read-only, or (if the kernel is Linux) to use the noatime mount
> option.
>
>     _______________________________________________________
>
> Reply to this item at:
>
>   <http://savannah.gnu.org/bugs/?51069>
>
> _______________________________________________
>   Message sent via/by Savannah
>   http://savannah.gnu.org/
>
>


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