[rrd-users] Struggling with rrdtool graph function.

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Wed Mar 27 14:52:43 CET 2013

----- Original Message ----- 
From: "Randy" <rrdtool at anr.net>
To: <rrd-users at lists.oetiker.ch>
Sent: Wednesday, March 27, 2013 1:55 PM
Subject: Re: [rrd-users] Struggling with rrdtool graph function.

>I get the concept. What I can't seem to wrap my head around is the
> specifics of how these statements fit together. If I had an example
> rrdgraph statement to look at that used these statement, it would
> help. I can't seem to find documentation that I can make heads or
> tails of or any examples. I even downloaded Router2 to try and look,
> but the programming there is way above me and I couldn't seem to pull
> out the relevant pieces.
> What I need is a concrete example to see and then go from there

Examples are available in the tutorial. The background color is changed, but 
you can equally easy modify your computations based on the decisions in 
those CDEFs.

In a nutshell:
RRDtool delivers timeslots with rates.  You are not interested in some 
First task for your CDEF: copy only those timeslots that are relevant, set 
the rest to zero or unknown.
Rates are valid between time T1 to time T2. Time in RRDtool defines the end 
of an interval, so T2.
You do not want midnight to 8am, so any timestamp that is on or before 8am 
should be discarded.
You do not want 10pm and after, so any timestamp that is after (and not: on) 
10pm should be discarded.
(timestamp 10pm defines e.g. 21:55 to 22:00 which you do want)
The CDEF programming for this part is available in the various examples on 
the net. The use of LTIME is probably a reasonable indicator that that piece 
of example code is useful for you.

In the tutorial the relevance is used to set a different background color.
You use the relevance to do or do not add the rate to your total.

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