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RRDs(3)               User Contributed Perl Documentation              RRDs(3)
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 ...
         RRDs::register_fetch_cb ...
         $RRDs::VERSION
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 ", $val;
           }
           print "\n";
         }
       RRDs::xport exposes the rrdxport functionality and returns data with
       the following structure:
         my ($start,$end,$step,$cols,$names,$data) = RRDs::xport ...
         # $start : timestamp
         # $end   : timestamp
         # $step  : seconds
         # $cols  : number of returned columns
         # $names : arrayref with the names of the columns
         # $data  : arrayref of arrayrefs with the data (first index is time, second is column)
       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.
   Fetch Callback Function
       Normally when using graph, xport or fetch the data you see will come
       from an actual rrd file.  Some people who like the look of rrd charts,
       therefore export their data from a database and then load it into an
       rrd file just to be able to call rrdgraph on it. Using a custom
       callback, you can supply your own code for handling the data requests
       from graph, xport and fetch.
       Todo this, you have to first write a fetch function in perl, and then
       register this function using "RRDs::fetch_register_callback".
       Finally you can use the pseudo path name cb//[filename] to tell rrdtool
       to use your callback routine instead of the normal rrdtool fetch
       function to organize the data required.
       The callback function must look like this:
         sub fetch_callback {
             my $args_hash = shift;
             # {
             #  filename => 'cb//somefilename',
             #  cd => 'AVERAGE',
             #  start => 1401295291,
             #  end => 1401295591,
             #  step => 300 }
             # do some clever thing to get that data ready
             return {
                 start => $unix_timestamp,
                 step => $step_width,
                 data => {
                     dsName1 => [ value1, value2, ... ],
                     dsName2 => [ value1, value2, ... ],
                     dsName3 => [ value1, value2, ... ],
                 }
            };
         }
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 AT oetiker.ch>
perl v5.26.3                      2019-11-25                           RRDs(3)