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I'm generating a number of graphs successfully with the awesome RRDTool application. However, I'm having some problems with the VRULE option while graphing.

I'm generating the graphs with a Bash script. For now I'm trying to draw a vertical red line at midnight (at UTC+02:00).

The code to get the last 2 midnight times in epoch:

NOW=`date +%s` DAY=86400 ZONE=7200 LDAY=$((NOW/DAY)) MID=$((LDAY*DAY)) SAST=$((MID-ZONE)) YEST=$((SAST-DAY))

So if I echo either $SAST or $YEST, it'll give me the epoch time at midnight last night or the day before.

Here's the working snippet for (one of) the graphs:

$RRDTOOL graph /var/www/images/graphs/wdata36h.png \ --title 'Pi Traffic Count (wlan0)' \ --watermark "Graph Drawn `date`" \ --vertical-label 'Bytes' \ --lower-limit '0' \ --rigid \ --alt-autoscale \ --units=si \ --width '700' \ --height '200' \ --full-size-mode \ --start end-36h \ 'DEF:wrx=/usr/local/bin/system/data.rrd:wrx:AVERAGE' \ 'DEF:wtx=/usr/local/bin/system/data.rrd:wtx:AVERAGE' \ 'AREA:wtx#0000FFFF:Upload\:' \ 'GPRINT:wtx:LAST:\:%8.2lf %s]' \ 'STACK:wrx#00CC00FF:Download\:' \ 'GPRINT:wrx:LAST:\:%8.2lf %s]'

As you can see, the graph spans the last 36 hours which includes 2 midnights. I've tried adding the $SAST and $YEST variables a few ways, but it keeps reading them as the variable names, not as the variable values.

I've tried adding:

'VRULE:$YEST#FF0000' \ 'VRULE:$SAST#FF0000' \

and

'VDEF:yest=$YEST' \ 'VDEF:sast=$SAST' \ 'VRULE:yest#FF0000' \ 'VRULE:sast#FF0000' \

But the quote marks are causing the variables to be interpreted as variable names.

I really do not want to recreate the data.rrd file as it has lots of historic data in it. This means that I'd need to draw those vertical lines in the graph stage and not the update stage.

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2 Answers 2

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I try to draw vertical line every 6 hour, it's my working script

#!/bin/sh NOW=`date +%s` DAY=86400 day6=21600 ZONE=10800 LDAY=$((NOW/DAY)) MID=$((LDAY*DAY)) SAST=$((MID-ZONE)) sa6=$((SAST+day6)) sa12=$((SAST+day6*2)) sa18=$((SAST+day6*3)) #YEST=$((SAST+43200)) bsd="/home/alex112/us/u2" #dat0=date -u -d $diff" +%-D rrdtool graph $bsd/temp01.png \ --watermark "Graph Drawn `date`" \ -w 600 -h 220 -v "Temperature" \ --upper-limit 10 --lower-limit -8 \ DEF:t11=$bsd/temp.rrd:t1:AVERAGE \ DEF:t12=$bsd/temp.rrd:t2:AVERAGE \ CDEF:ct11=t11,10,/ \ CDEF:ct12=t12,10,/ \ LINE1:ct11#00FF00:"fridge" \ LINE1:ct12#0000FF:"stock" \ HRULE:0#000000:"Zero Level" \ HRULE:8#FF0000:"Max temp" \ HRULE:-6#FF0000:"Min Fridge" \ VRULE:$SAST#FF0000: \ VRULE:$sa6#FF0000: \ VRULE:$sa12#FF0000: \ VRULE:$sa18#FF0000:"Zero time"
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  • How does this answer the question? Commented Sep 28, 2018 at 18:09
  • This gave me enough information to work out how I needed to implement a VRULE, so it certainly has value as an answer. Commented Aug 24, 2022 at 8:09
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After a LOT of trial and error (more on this below)

I found that I can't have all the arguments in quotes.

I ended up with this:

$RRDTOOL graph /var/www/images/graphs/wdata36h.png \ --title 'Pi Traffic Count (wlan0)' \ --watermark "Graph Drawn `date`" \ --vertical-label 'Bytes' \ --lower-limit '0' \ --rigid \ --alt-autoscale \ --units=si \ --width '700' \ --height '200' \ --full-size-mode \ --start end-36h \ 'DEF:wrx=/usr/local/bin/system/data.rrd:wrx:AVERAGE' \ 'DEF:wtx=/usr/local/bin/system/data.rrd:wtx:AVERAGE' \ 'AREA:wtx#0000FFFF:Upload\:' \ 'GPRINT:wtx:LAST:\:%8.2lf %s]' \ 'STACK:wrx#00CC00FF:Download\:' \ 'GPRINT:wrx:LAST:\:%8.2lf %s]' \ VRULE:$YEST#FF0000 \ VRULE:$SAST#FF0000

I tried concatenating the entire graph into one variable and then running that variable, but it failed spectacularly as it was removing the single quotes and then believed that any space meant a new command or function resulting in errors like ERROR: 'T' is not a valid function name (from the "T" in --title 'Pi Traffic Count (wlan0)').

Then I tried removing all the spaces physically (and with \)but still got the same error, this time it was from me generating today's date:

--watermark "Graph Drawn `date`"

Which happens to be "Thursday".

Hope this helps someone with the same problem I had.

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