2012-05-31

rrdtool lastupdate

A variety of tools use RRD databases which are ideal for recording a sequence of values over time.  So one interesting question is when the last time the rrd file was updated - rrdtool's lastupdate mode will tell you.
$ rrdtool lastupdate probe302Value_probe302Value.rrd
1334603585: 190.0
Text 1:   The most recent value in the RRD is 190.0 recorded at 1334603585
The value of the time is a UTC timestamp.  Converting this value to a readable date/time can be performed using the UN*X date command.
$ date -d '@1334603681'
Mon Apr 16 15:14:41 EDT 2012
Text 2: Converting a timestamp to a date/time.
With knowing the last update and most recent value you can verify that the database is being updated at the correct interval and with the expected values.

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