[rrd-users] What is "'SCALAR' is not a valid function name"?

Bartman bartman70 at yahoo.com
Tue May 12 17:32:10 CEST 2009

Having similar issue.  Have seen this question in a few places and no
response.  The following command line works for me:

rrdtool graph bart1.png --start 1242118758 --end 1242119433
DEF:mytemp=cpu-system.rrd:value:AVERAGE LINE2:mytemp#0000FF

However, trying to run it in perl as below:

#!/usr/bin/perl -w

use lib qw( /usr/local/rrdtool-1.3.4/lib/perl );
use RRDs;

my $cur_time = time();
my $end_time = $cur_time;
my $start_time = $end_time - 300;

print "start time: $start_time\n";
print "end time: $end_time\n";

RRDs::graph("bartgen.png", \
        "--start=1242118758", \
        "--end=1242119433", \
        "DEF:system=cpu-system.rrd:value:AVERAGE", \

my $err=RRDs::error;
if ($err) {print "problem generating the graph: $err\n";}

print "end of script\n\n";

gives me a 'SCALAR' is not a valid function name error.


Grace Tsai wrote:
> Hi,
> I am a beginner of using RRDtool. I am writing a Perl script to read 
> data from a RRDtool database and generate a graph.
> But I got error
> 'SCALAR' is not a valid function name
> from the step:
> RRDs::graph (...
> Can you give me some advice please? Thanks.
> Grace

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