[rrd-users] Re: PREV fails?

[Alex van den Bogaerdt]

Tobias Oetiker wrote:
> *> I tried something like:
> *> 
> *>    DS:t=blah.rrd:usertime
> *>    CDEF:tt=t,PREV,-
> *> 
> *> In other words, I tried to work with the difference between the
> *> previous value and the current one.  Obviously, it doesn't work this way.
> *> 
> *> I'm sure I'll work around this sometime.
> 
> this will work, but you must guard against getting any unknowns in there ...
> at first PREV will be UNKNOWN. This will propageat ... 
> 
Nope, this is not all.

PREV is the previous value of the outcome of the CDEF.
This means that:

input DS
1
10
100
1000

CDEF outcome:
10-1==9
100-9==91
1000-91==909

I tried to get:
10-1==9
100-10==90
1000-100==900


regards,
-- 
   __________________________________________________________________
 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
| work                                                         private |
| My employer is capable of speaking therefore I speak only for myself |
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