NAME¶
RRDs - Access RRDtool as a shared module
SYNOPSIS¶
use RRDs;
RRDs::error
RRDs::last ...
RRDs::info ...
RRDs::create ...
RRDs::update ...
RRDs::updatev ...
RRDs::graph ...
RRDs::fetch ...
RRDs::tune ...
RRDs::times(start, end)
RRDs::dump ...
RRDs::restore ...
RRDs::flushcached ...
DESCRIPTION¶
Calling Sequence¶
This module accesses RRDtool functionality directly from within Perl. The
arguments to the functions listed in the SYNOPSIS are explained in the regular
RRDtool documentation. The command line call
rrdtool update mydemo.rrd --template in:out N:12:13
gets turned into
RRDs::update ("mydemo.rrd", "--template", "in:out", "N:12:13");
Note that
--template=in:out
is also valid.
The RRDs::times function takes two parameters: a "start" and
"end" time. These should be specified in the
AT-STYLE TIME
SPECIFICATION format used by RRDtool. See the
rrdfetch
documentation for a detailed explanation on how to specify time.
Error Handling¶
The RRD functions will not abort your program even when they can not make sense
out of the arguments you fed them.
The function RRDs::error should be called to get the error status after each
function call. If RRDs::error does not return anything then the previous
function has completed its task successfully.
use RRDs;
RRDs::update ("mydemo.rrd","N:12:13");
my $ERR=RRDs::error;
die "ERROR while updating mydemo.rrd: $ERR\n" if $ERR;
Return Values¶
The functions RRDs::last, RRDs::graph, RRDs::info, RRDs::fetch and RRDs::times
return their findings.
RRDs::last returns a single INTEGER representing the last update time.
$lastupdate = RRDs::last ...
RRDs::graph returns an ARRAY containing the x-size and y-size of the
created image and a pointer to an array with the results of the PRINT
arguments.
($result_arr,$xsize,$ysize) = RRDs::graph ...
print "Imagesize: ${xsize}x${ysize}\n";
print "Averages: ", (join ", ", @$averages);
RRDs::info returns a pointer to a hash. The keys of the hash represent
the property names of the RRD and the values of the hash are the values of the
properties.
$hash = RRDs::info "example.rrd";
foreach my $key (keys %$hash){
print "$key = $$hash{$key}\n";
}
RRDs::graphv takes the same parameters as
RRDs::graph but it
returns a pointer to hash. The hash returned contains meta information about
the graph. Like its size as well as the position of the graph area on the
image. When calling with and empty filename than the contents of the graph
will be returned in the hash as well (key 'image').
RRDs::updatev also returns a pointer to hash. The keys of the hash are
concatenated strings of a timestamp, RRA index, and data source name for each
consolidated data point (CDP) written to disk as a result of the current
update call. The hash values are CDP values.
RRDs::fetch is the most complex of the pack regarding return values.
There are 4 values. Two normal integers, a pointer to an array and a pointer
to a array of pointers.
my ($start,$step,$names,$data) = RRDs::fetch ...
print "Start: ", scalar localtime($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";
}
RRDs::times returns two integers which are the number of seconds since
epoch (1970-01-01) for the supplied "start" and "end"
arguments, respectively.
See the examples directory for more ways to use this extension.
NOTE¶
If you are manipulating the TZ variable you should also call the POSIX function
tzset(3) to initialize all internal state of the library for properly
operating in the timezone of your choice.
use POSIX qw(tzset);
$ENV{TZ} = 'CET';
POSIX::tzset();
AUTHOR¶
Tobias Oetiker <tobi@oetiker.ch>