[rrd-developers] Re: re fetching most recent DS values

steve rader rader at ginseng.hep.wisc.edu
Wed May 23 21:00:49 MEST 2001

 > how about using -s now-<update interval> ? this should always yeald
 > valid data ...

Close but not quite.  It appears that I'd have to use the first
value returned because there's no test for the second value that
will tell me if it's the most recent (because NaN can happen when
the DS is updated with U or when the update hasn't happened.)

So I'd have to always use the second value returned.  And in that
case, sometimes I won't be using the most recent data value...
in other words, when RRDs have been updated since the last
CDP time slot passed, the values won't match the values from
"rrdtool graph [...] GPRINT:vname:LAST" et al.

(Btw, why is the last value returned by rrdtool fetch NaN at
the next CDP time slot in the future??!)

 > on another note the perl/C interface is described in the perl
 > documentation .. use perldoc perl to get started .... there are
 > several perl pods on this subject

Okay, but specifically: say I get "rrdtool recent-values" working (in
the src dir), where do I find doc about fixing up perl-shared/RRDs.xs
to allow for

  use RRDs;
  (@val_details) = RRDs::recent-values @current_val_fetch;


(Tobi, have you noticed that this seems like another permutation
of the recent/current/now/last issue(s) I keep bugging you about?!)

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