Cacti and rrdtool

After a few hours' worth of wrangling, I think I've tamed rrdtool into producing a sane graph for devices that report temperatures in degrees C multiplied by 10:

/usr/bin/rrdtool graph test.png --imgformat=PNG --start=-86400 --end=-300 --title="rm-mon-1 - Rack A18" --base=1000 --height=120 --width=500 --alt-autoscale-max --lower-limit=0 --vertical-label="degrees C x 10" --font TITLE:12: --font AXIS:8: --font LEGEND:10: --font UNIT:8: DEF:a=rra/rm-mon-1_snmp_oid_138.rrd:snmp_oid:AVERAGE DEF:b="rra/rm-mon-1_snmp_oid_138.rrd":snmp_oid:MAX CDEF:cdefa=a,0.1,'*' CDEF:cdefb=b,10,/ LINE:cdefa#F50000FF:"degrees C" GPRINT:cdefa:LAST:"Current\:%8.2lf %s" GPRINT:cdefa:AVERAGE:"Average\:%8.2lf %s" GPRINT:cdefb:MAX:"Maximum\:%8.2lf %s\n"

The magic is in the CDEF statements, which declares a variable (for example, cdefa) then assigns to it the value of a with a RPN modifier - in this case 10,/ (divide by 10)

The other magic is to then remember to USE the newly-assigned cdefa rather than straight a as values used by LINE and GPRINT statements (it took me a while to realise that I was happily assigning the correct value to cdefa and cdefb and then never using them.

I'm yet to figure out how to wrangle this data into cacti - so far I'm just fooling around in bash. I'm sure I'll figure it out... later.

For bonus points:

• assign more meaningful variables names than a, b, cdefa and cdefb - these are the defaults I got from cacti, but they should really be r18_avg_temp_by_ten, r18_max_temp_by_ten, r18_avg_temp, r18_max_temp
• plot all related rack temps on the same single graph - they're drawn from multiple rrd files, but that should be easy enough
  

Getting the track listing for a K3B project

This was harder than I expected. However...

Get your .k3b file, which is really a zip file:

$ unzip -l can-u-pick-em.k3b
Archive: can-u-pick-em.k3b
Length Date Time Name
--------- ---------- ----- ----
17 2106-02-07 17:28 mimetype
10623 2106-02-07 17:28 maindata.xml
--------- -------
10640 2 files

and extract the only useful part:

unzip -p can-u-pick-em.k3b maindata.xml > tmp.xml

That's an XML file that contains the project data. Then we feed it through an XSLT processor, using this stylesheet:


<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/1999/xhtml">

<xsl:output method="text" encoding="UTF-8"/>

<xsl:template match="/k3b_audio_project">
<xsl:apply-templates select="contents">
</xsl:apply-templates>
</xsl:template>


<xsl:template match="contents">
<xsl:apply-templates select="track">
</xsl:apply-templates>
</xsl:template>

<xsl:template match="track">
<xsl:value-of select="cd-text/artist"/>
<xsl:text> - </xsl:text>
<xsl:value-of select="cd-text/title"/>
<xsl:text>
</xsl:text>
</xsl:template>

</xsl:stylesheet>


like this:

$ xsltproc stylesheet.xslt tmp.xml
Eleni Mandell - Pauline
Neko Case - Star Witness

etc

EDIT!
Another option which I tried initially was using dcop to interrogate K3B while it has the project open - there are tons of suggestions out there to do this, but I could never get it to work. It turns out that dcop doesn't work in KDE4, and has been replaced with DBUS. Ah, so here's some examples using DBUS to talk to amarok - so maybe this will work... though this suggests otherwise