[rrd-users] Print MAX with date

[Alex van den Bogaerdt]

> Hi folks,
>
> I am wondering how to make a graph with the date and time of maximum
> value.
> Actually I do it this way:
> 'DEF:a_temperatur_max=/home/pi/wetter.rrd:aussentmp:MAX‘ \
> 'VDEF:a_temp_max=a_temperatur_max,MAXIMUM' \
> 'GPRINT:a_temp_max:max\: %5.2lf °C'

First of all: that GPRINT is not supposed to work.

These should work
a) GPRINT:<cdef-name>:<cf>:<format>
b) GPRINT:<vdef-name>:<format>

this is what you just wrote:
c) GPRINT:<vdef-name>:<cf>:<format>       <--- bad example

There's nothing to consolidate, a VDEF contains a single rate. That's why
it should not have a CF. I'm surprised to learn that it works this way
instead of generating an error.


>
> But would like to print the time of the maximum value also. Any hints?

a_temp_max contains both the consolidated rate (e.g. your MAX) as well as
the time this occurred. Just print it another time, now with %X as
formatter.

Open https://oss.oetiker.ch/rrdtool/doc/rrdgraph_graph.en.html and find
'%X' on that page, there's all you want to know.

HTH
Alex