Section: User Contributed Perl Documentation (3)
RRDp - Attach RRDtool from within a perl script via a set of pipes;
RRDp::start path to RRDtool executable
RRDp::cmd rrdtool commandline
$answer = RRD::read
$status = RRD::end
$RRDp::user, $RRDp::sys, $RRDp::real, $RRDp::error_mode, $RRDp::error
With this module you can safely communicate with the RRDtool.
After every RRDp::cmd you have to issue an RRDp::read command to get
RRDtools answer to your command. The answer is returned as a pointer,
in order to speed things up. If the last command did not return any
data, RRDp::read will return an undefined variable.
If you import the PERFORMANCE variables into your namespace,
you can access RRDtool's internal performance measurements.
- use RRDp
Load the RRDp::pipe module.
- RRDp::start path to RRDtool executable
start RRDtool. The argument must be the path to the RRDtool executable
- RRDp::cmd rrdtool commandline
pass commands on to RRDtool. Check the RRDtool documentation for
more info on the RRDtool commands.
Note: Due to design limitations, RRDp::cmd does not support the
"graph -" command - use "graphv -" instead.
- $answer = RRDp::read
read RRDtool's response to your command. Note that the $answer variable will
only contain a pointer to the returned data. The reason for this is, that
RRDtool can potentially return quite excessive amounts of data
and we don't want to copy this around in memory. So when you want to
access the contents of $answer you have to use $$answer which dereferences
- $status = RRDp::end
terminates RRDtool and returns RRDtool's status ...
- $RRDp::user, $RRDp::sys, $RRDp::real
these variables will contain totals of the user time, system time and
real time as seen by RRDtool. User time is the time RRDtool is
running, System time is the time spent in system calls and real time
is the total time RRDtool has been running.
The difference between user + system and real is the time spent
waiting for things like the hard disk and new input from the Perl
- $RRDp::error_mode and $RRDp::error
If you set the variable $RRDp::error_mode to the value 'catch' before you run RRDp::read a potential
ERROR message will not cause the program to abort but will be returned in this variable. If no error
occurs the variable will be empty.
$RRDp::error_mode = 'catch';
RRDp::cmd qw(info file.rrd);
print $RRDp::error if $RRDp::error;
RRDp::cmd qw(create demo.rrd --step 100
$answer = RRDp::read;
($usertime,$systemtime,$realtime) = ($RRDp::user,$RRDp::sys,$RRDp::real);
For more information on how to use RRDtool, check the manpages.
Tobias Oetiker <firstname.lastname@example.org