Do we want a periodic script for a zfs scrub?

[Artem Belevich]

You can do something like this:

#SCRUB_TS="2010-06-08.20:51:12"
SCRUB_TS=$1
# parse timestamp, move it forward by 1 month and print in seconds since Epoch
NEXT_SCRUB_DATE_S=`date -j -f "%Y-%m-%d.%H:%M:%S" -v+1m +"%s" $SCRUB_TS`
# for debugging purposes convert epoch time into something human-readable
NEXT_SCRUB_DATE=`date -r $NEXT_SCRUB_DATE`
# surrent time in secs since Epoch.
NOW_S=`date +"%s"`
# Compare two times to figure out if next scrub time is still in the future
if [ $NOW_S -gt $NEXT_SCRUB_DATE_S ]; then
    echo yup.
else
    echo nope.
fi

--Artem



On Thu, Jun 10, 2010 at 8:38 AM, Alexander Leidinger
<Alexander at leidinger.net> wrote:
> Quoting Artem Belevich <fbsdlist at src.cx> (from Thu, 10 Jun 2010 07:59:46
> -0700):
>
>>> Good idea! I even found a command line which does the calculation for the
>>> number of days between "now" and the last run (not taking a leap year
>>> into
>>> account, but an off-by-one day error here does not matter).
>>
>> You can get exactly one month difference by using -v option of 'date'
>> command to figure out the time/date offset by arbitrary amount.
>> Combined with +"%s" format to print number of seconds since Epoch and
>> -r to specify the reference point in time it makes 'date' pretty
>> useful in scripts.
>
> What we have is the date of the last scrub (e.g. 2010-06-08.20:51:12), and
> what we want to know is if between the last scrub and now we passed a
> specific amount of days or not.
>
> What I do is taking the year multiplied with 365 plus the day of the year.
> Both of this for the last date of the scrub and "now". The difference is the
> number of days between those two dates. This value I can use with -le or -ge
> for the test command.
>
> This is only off by one once in a leap year when the leap-day is in-between
> the two dates (those people which want to scrub every 4 years are off by two
> when both leap-days are in-between, but a scrub of every 4 years or more
> looks unreasonable to me, so I do not care much about this).
>
> This is done in one line with two calls to date (once for the last scrub,
> once for "now") and a little bit of shell-buildin-arithmetic. If you have a
> more correct version which is not significantly more complex, feel free to
> share it here.
>
> Bye,
> Alexander.
>
> --
>  "Who would have though hell would really exist? And that it would be in New
> Jersey?" -Leela
> "Actually..." - Fry
>
> http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
> http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137
>