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RRDGRAPH_DATA(1)		    rrdtool		      RRDGRAPH_DATA(1)

NAME
       rrdgraph_data - preparing data for graphing in rrdtool graph

SYNOPSIS
       DEF:<vname>=<rrdfile>:<ds-
       name>:<CF>[:step=<step>][:start=<time>][:end=<time>][:reduce=<CF>]

       VDEF:vname=RPN expression

       CDEF:vname=RPN expression

DESCRIPTION
       These  three instructions extract data values out of the	RRD files, op-
       tionally	altering them (think, for example, of a	bytes to bits  conver-
       sion).  If  so desired, you can also define variables containing	useful
       information such	as maximum, minimum etcetera. Two of the  instructions
       use a language called RPN which is described in its own manual page.

       Variable	names (vname) must be made up strings of the following charac-
       ters "A-Z, a-z, 0-9, -,_" and a maximum length of 255 characters.

       When picking variable names, make sure you do not choose	a name that is
       already	taken  by  an  RPN operator. A save bet	it to use lowercase or
       mixedcase names for variables since operators will always be in	upper-
       case.

DEF
       DEF:<vname>=<rrdfile>:<ds-
       name>:<CF>[:step=<step>][:start=<time>][:end=<time>][:reduce=<CF>]

       This command fetches data from an RRD file.  The	virtual	name vname can
       then  be	 used  throughout  the	rest of	the script. By default,	an RRA
       which contains the correct consolidated data at an appropriate  resolu-
       tion  will be chosen.  The resolution can be overridden with the	--step
       option.	The resolution can again be overridden by specifying the  step
       size.   The  time span of this data is the same as for the graph	by de-
       fault, you can override this by specifying start	and end.  Remember  to
       escape colons in	the time specification!

       If  the	resolution  of	the  data is higher than the resolution	of the
       graph, the data will be further consolidated.  This  may	 result	 in  a
       graph that spans	slightly more time than	requested.  Ideally each point
       in the graph should correspond with one CDP from	an RRA.	 For instance,
       if  your	 RRD has an RRA	with a resolution of 1800 seconds per CDP, you
       should create an	image with width 400 and time  span  400*1800  seconds
       (use    appropriate   start   and   end	 times,	  such	 as   "--start
       end-8days8hours").

       If consolidation	needs to be done, the CF of the	RRA specified  in  the
       DEF  itself will	be used	to reduce the data density. This behaviour can
       be changed using	":reduce=<CF>".	 This optional parameter specifies the
       CF to use during	the data reduction phase.

       Example:

	       DEF:ds0=router.rrd:ds0:AVERAGE
	       DEF:ds0weekly=router.rrd:ds0:AVERAGE:step=7200
	       DEF:ds0weekly=router.rrd:ds0:AVERAGE:start=end-1h
	       DEF:ds0weekly=router.rrd:ds0:AVERAGE:start=11\:00:end=start+1h

VDEF
       VDEF:vname=RPN expression

       This command returns a value and/or a time according to the RPN	state-
       ments  used. The	resulting vname	will, depending	on the functions used,
       have a value and	a time component.  When	you use	this vname in  another
       RPN  expression,	you are	effectively inserting its value	just as	if you
       had put a number	at that	place.	The variable can also be used  in  the
       various graph and print elements.

       Example:	"VDEF:avg=mydata,AVERAGE"

       Note  that currently only agregation functions work in VDEF rpn expres-
       sions.  Patches to change this are welcome.

CDEF
       CDEF:vname=RPN expression

       This command creates a new set of data points (in memory	only,  not  in
       the  RRD	 file)	out of one or more other data series. The RPN instruc-
       tions are used to evaluate a mathematical function on each data	point.
       The  resulting vname can	then be	used further on	in the script, just as
       if it were generated by a DEF instruction.

       Example:	"CDEF:mydatabits=mydata,8,*"

SEE ALSO
       rrdgraph	gives an overview of how rrdtool graph	works.	 rrdgraph_data
       describes  DEF,CDEF and VDEF in detail.	rrdgraph_rpn describes the RPN
       language	used in	the ?DEF statements.   rrdgraph_graph  page  describes
       all of the graph	and print functions.

       Make sure to read rrdgraph_examples for tips&tricks.

AUTHOR
       Program by Tobias Oetiker <tobi@oetiker.ch>

       This manual page	by Alex	van den	Bogaerdt <alex@ergens.op.het.net>

1.2.30				  2009-01-19		      RRDGRAPH_DATA(1)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=rrdgraph_data&sektion=1&manpath=FreeBSD+Ports+14.3.quarterly>

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