RRDs - Access rrdtool as a shared module

# NAME

RRDs - Access rrdtool as a shared module

# SYNOPSIS

      use RRDs::ext
      RRDs::error
      RRDs::last ...
      RRDs::create ...
      RRDs::update ...
      RRDs::graph ...
      RRDs::fetch ...
      RRDs::tune ...

# 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 commandline call

     rrdtool update mydemo.rrd N:12:13

gets turned into

     RRDs::update qw(mydemo.rrd N:12:13);

## Error Handling

The RRD functions will not abort your program even when they can not make sense out of the arguments you fed them. There are two ways to determine if an error has occured.

First the every function will return the value -1 if an error occured. Second, the function RRDs::error can be called to get the error message from the last function call. If RRDs::error does not return an error then the previous function has completed its task succesfully.

     RRDs::update qw(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 and RRDs::fetchgive return their findigs.

RRDs::last returns a single INTEGER representing the last update time.

     $lastupdate = RRDs::last ...

RRDs::graph returns an pointer to an ARRAY containing the x-size and y-size of the created gif and results of the PRINT arguments.

     ($averages,$xsize,$ysize) = RRDs::graph ...
     print "Gifsize: ${xsize}x${ysize}\n";
     print "Averages: ", (join ", ", @$averages);

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:        ".localtime($start)."\n";
     print "Stepsize:     $step seconds\n";
     print "Column Names: ".join (", ", @$names)."\n";
     print "Date:\n";
     foreach my $line (@$array){
          print "".localtime($start),"   ";
          $start += $step;
          foreach my $val (@$line) {
               printf "%12.1f", $val;
          }
          print "\n";
     }

See the examples directory for more ways to use this extension.

# AUTHOR

Tobias Oetiker