* utimensat and AT_EMPTY_PATH
@ 2017-04-10 16:05 Ian Pilcher
2017-04-13 17:11 ` Florian Weimer
0 siblings, 1 reply; 3+ messages in thread
From: Ian Pilcher @ 2017-04-10 16:05 UTC (permalink / raw)
To: libc-help
Given a file descriptor that refers to a symbolic link, is there a way
to call utimensat (or some other function) to update its timestamp?
I.e. what I would like to do is:
utimensat(linkfd, "", times, AT_EMPTY_PATH);
Unlike futimens, utimensat *can* update the timestamp of a symlink
(verified with "strace touch -h ..."), but it doesn't seem to accept
AT_EMPTY_PATH.
Is there any non-racy way to do this?
--
========================================================================
Ian Pilcher arequipeno@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: utimensat and AT_EMPTY_PATH
2017-04-10 16:05 utimensat and AT_EMPTY_PATH Ian Pilcher
@ 2017-04-13 17:11 ` Florian Weimer
2017-04-13 20:40 ` Ian Pilcher
0 siblings, 1 reply; 3+ messages in thread
From: Florian Weimer @ 2017-04-13 17:11 UTC (permalink / raw)
To: Ian Pilcher, libc-help
On 04/10/2017 06:05 PM, Ian Pilcher wrote:
> Given a file descriptor that refers to a symbolic link, is there a way
> to call utimensat (or some other function) to update its timestamp?
>
> I.e. what I would like to do is:
>
> utimensat(linkfd, "", times, AT_EMPTY_PATH);
>
> Unlike futimens, utimensat *can* update the timestamp of a symlink
> (verified with "strace touch -h ..."), but it doesn't seem to accept
> AT_EMPTY_PATH.
>
> Is there any non-racy way to do this?
Usually, it's possible to use the non-f, non-at system call variants
with a /proc/fd/%d path. Those appear as symbolic links in the proc
file system, but they actually are not, and the kernel will do the right
thing even when operating on O_PATH descriptors.
Florian
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: utimensat and AT_EMPTY_PATH
2017-04-13 17:11 ` Florian Weimer
@ 2017-04-13 20:40 ` Ian Pilcher
0 siblings, 0 replies; 3+ messages in thread
From: Ian Pilcher @ 2017-04-13 20:40 UTC (permalink / raw)
To: libc-help
On 04/13/2017 12:11 PM, Florian Weimer wrote:
> Usually, it's possible to use the non-f, non-at system call variants
> with a /proc/fd/%d path. Those appear as symbolic links in the proc
> file system, but they actually are not, and the kernel will do the right
> thing even when operating on O_PATH descriptors.
Works for me. Thank you!
--
========================================================================
Ian Pilcher arequipeno@gmail.com
-------- "I grew up before Mark Zuckerberg invented friendship" --------
========================================================================
^ permalink raw reply [flat|nested] 3+ messages in thread
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