[rrd-users] Re: Q: How to fetch value from "start" to "end" in

[Alex van den Bogaerdt]

Alex Lam wrote:

> So, the NOW reference is NOT useful to me.  In order to extract the data 
> during the
> interval (from start to end time), I REALLY need to get the "start", "last" 
> and/or "end"
> value stored in the RRD database.

[...]

> So, I really need to know how to fetch data from start to end (or last) .
> 
> In addition, "rrdtool fetch " can refer to the start and end value, why 
> can't I use
> "rrdtool fetch RRD CF  --start s --end e"       OR
> "rrdtool info"
> to get the start, end timestamp value?


"--start s" means "--start start" and as I said, this does not mean
the start of the data.  It means the start of your query.  Same applies
for "--end e".

You can get the last update timestamp with "rrdtool last".

This is not useful if you also need the first update.  Try rrdtool
dump and view the output.  Each RRA will have a series of time in it.

Each RRA will look like
   <some timestamp;first line>
   ...
   <most recent timestamp; timestamp can be obtained by "rrdtool last">
   <least recent timestamp>
   ...
   <some timestamp; last line>

If the RRA is big enough to hold *all* measured data it will look like:
   <some timestamp;data == NaN;first line>
   ...
   <some timestamp;data == NaN>
   <some timestamp;data != NaN;first logged value>
   ...
   <most recent timestamp; last line>


HTH
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