[rrd-users] Beginner question: "rrdtool.exe graph" started from windows shell does not produce any graph nor error message
Alex van den Bogaerdt
alex at vandenbogaerdt.nl
Wed Jan 8 14:18:17 CET 2014
> I have read both manual and tutorial again and discovered missed parameter
> It`s pitty the author hide this important sentence at the very end of
> document: "You need at least one DEF and one LINE, AREA, GPRINT, PRINT
> statement to generate anything useful"
> Should I consider those parameters as a mandatory minimum? Without
> AREA,GPRINT and PRINT, still got valid graph. Can someone explain me this?
There is no such thing as a mandatory line or a mandatory area. And if you do
not want a legend line from GPRINT then that too is just fine. If you do
not ask RRDtool to produce any output, it will not produce output. It did
exactly what you asked it to do, so there's no error either.
It's perfectly fine to just draw a line without any legend. You'd need a DEF
and a LINE. Also fine is a legend without a line; you'd need a DEF and a
GPRINT command. Whether or not that's useful, is your decision.
It's perfectly fine to just have a DEF and a PRINT. No graph created, there
will be only a number returned to the calling process. Again, that is not an
error condition, it is what you ask RRDtool to do.
If you did not yet 'get it' yet, maybe you paced through the tutorial too
get data: DEF
massage data: CDEF
output data: LINE, AREA, PRINT, GPRINT. Choose zero or more.
and you should look at XPORT, which is not covered in the tutorial because
the tutorial was written in the v1.0 era of rrdtool and XPORT came later.
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