Getting "absolute" time in Linux

Is there a way in either standard or Real-time Linux to get "absolute
number of ticks (or seconds) since the Epoc (or some other configurable
starting point), regardless of the kernel clock resets via
settimeofday() and the RTC resets via hwclock set and regardless of the
system reboots?

In comp.os.linux.networking Boris Benenson <(E-Mail Removed)>:
> Is there a way in either standard or Real-time Linux to get "absolute
> number of ticks (or seconds) since the Epoc (or some other configurable
> starting point), regardless of the kernel clock resets via
> settimeofday() and the RTC resets via hwclock set and regardless of the
> system reboots?

man date
/%s

Good luck

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Michael Heiming (X-PGP-Sig > GPG-Key ID: EDD27B94)
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Boris Benenson <(E-Mail Removed)> wrote:
> Is there a way in either standard or Real-time Linux to get
> "absolute number of ticks (or seconds) since the Epoc (or some other
> configurable starting point), regardless of the kernel clock resets
> via settimeofday() and the RTC resets via hwclock set and regardless
> of the system reboots?

"Absolute" relative to what? Anything on the system itself reporting
seconds will be subject to the vagaries of drift relative to other
systems/"true time" (if such a thing exists). (humor involving
general relativity etc omitted

rick jones
--
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Michael Heiming <michael+(E-Mail Removed)> writes:

>In comp.os.linux.networking Boris Benenson <(E-Mail Removed)>:
>> Is there a way in either standard or Real-time Linux to get "absolute
>> number of ticks (or seconds) since the Epoc (or some other configurable

Do you mean real time or ticks of the computer clock?

>> starting point), regardless of the kernel clock resets via
>> settimeofday() and the RTC resets via hwclock set and regardless of the
>> system reboots?

What have kernel resets of rtc got to do with true time?


>man date
>/%s

That may or may not be a place to start.
Note that you want to make sure your clock is on true time ( ntp or chrony
should ensure that)

Boris Benenson wrote:
> Is there a way in either standard or Real-time Linux to get "absolute
> number of ticks (or seconds) since the Epoc (or some other configurable
> starting point), regardless of the kernel clock resets via
> settimeofday() and the RTC resets via hwclock set and regardless of the
> system reboots?

The 'time' function gives you the system's best estimate of the number
of seconds since the epoch. If that's what you want, that's the
function that gives it to you.

I don't know what you mean by regardless of kernel clock restets via
'settimeofday'. Presumably, if someone called 'gettimeofday', it was
because they had reason to believe it would improve the kernel's
estimate of the time since the epoch. If not, why would they have
called 'gettimeofday'?

DS