[rrd-users] PRINT to stdout - I give up - SOLVED

[EA Kissack]

On 06.02.2012 07:49, Steve Shipway wrote:
> Looking at your script, you are not retrieving the return value of
> RRDs::graph(), which is where the PRINT output goes.  It does not go
> to stdout.
>
> You should do:
>
>      @rv = RRDs::graph(@rrd);
>
> Then, @rv = ( @output, $xsize, $ysize ) for a graph image $xsize by
> $ysize, and @output is the array of all the PRINT output.
>
> See the manual for details: 
> http://oss.oetiker.ch/rrdtool/prog/RRDs.en.html
>
> It might be more efficient though to use RRDs::fetch to collect
> averages for the various DSs and then do the multiplication and
> summation in your perl code, rather than go through all the graphing
> only to throw the image away...
>
> Steve
>
> Steve Shipway
> University of Auckland ITS
> UNIX Systems Design Lead
> s.shipway at auckland.ac.nz
> Ph: +64 9 373 7599 ext 86487

Steve

Thanks again.  I couldn't get the first suggestion to work, but 
RRDs::fetch did work after a bit of extra googling.  I used:
sub nographtrial {
     my ($start,$step,$names,$data) = 
RRDs::fetch("/var/log/rrd/bwin.rrd", "AVERAGE", "-s -300", "-e -300") ;
     print "Start:       ", scalar localtime($start), " ($start)\n";
     print "Step size:   $step seconds\n";
     print "DS names:    ", join (", ", @$names)."\n";
     print "Data points: ", $#$data + 1, "\n";
     print "Data:\n";
     for my $line (@$data) {
       print "  ", scalar localtime($start), " ($start) ";
       $start += $step;
       for my $val (@$line) {
         printf "%12.1f ", $val;
       }
       print "\n";
     }
}
and can now see the latest data points.  I just need to remember, now, 
why I wanted the data in the first place :-)

Allan