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

From: James Youngman
Subject: Re: [bug #51069] find changes access time on directories
Date: Sun, 21 May 2017 09:24:20 +0100

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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