[collectd] feeding "unknown" values to the rrdtool writer from my plugin

Andreas Schuldei andreas at schuldei.org
Thu Mar 16 19:36:00 CET 2017

on the rrdtool-user mailinglist i learned that unknown values were
indicated to rrdlib with the char "U". Now, that i set unknown values in my
plugin to "U", i get this error in the logs:

Argument "U" isn't numeric in subroutine entry at
/usr/share/perl5/Collectd/Plugins/OneWireCtlr.pm line 135 - which is the

so please help me out, how do i tell collectd that a value is unknown, and
should be teated as such?

On Wed, Mar 15, 2017 at 10:41 AM Andreas Schuldei <andreas at schuldei.org>

> Hi,
> i would like to be able to feed the rrdtool backend the "unknown" value at
> appropriate times.
> my plugin is written in perl, and i read collecd uses the rrdlib - but i
> find different notations when looking for the right way to say "unknown".
> What is the correct notation in my perl plugin for unknown values, so that
> rrdtool does the right thing?
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