[rrd-users] Block GPRINT when values not defined?

[Johan Elmerfjord]

Hi,

I'm working with some linear predictions and want to print out when some limits are about to be reached.

Today I'm using LIMIT to filter out when we are between the 2 thresholds (say 90-100%).
Then I'm taking the FIRST and LAST value for this sequence - that gives me the 90-time and 100-time.
Then I print these out using a line like:  'GPRINT:minpred:Reaching 90 on \: %c\n:strftime'

The problem is that if the minpred-time is undefined due to that we don't have a "growing enough" trend, and therefor can't estimate when we will hit the 90-% limit,
we end up sending undef or 0 to strftime - which will then print  Jan 1 01:00:00 1970.

Is there a way that I can check these values - and only do GPRINT if I have a valid timestamps?
Is it possible with RPN to do this?
I do want to use the strftime as that allows me to format the unix timestamp before printing it.

Are there other ways?
I could probably export the prediction data first - in a pre-graphing processing - and only add the values if they are good.
But if it can be done in one single step , that would be great.

/Johan
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