Getting deltas

Hello

I hope someone can help/explain this to me :)


I have a SNMP counter that will go up (never down until the app is
restarted)
and what I need to to plot is the different (delta) between 2 point...

say at time-a  : value is 0
          time-b  : value is 5
          time-c : value is 17
          time-d : value is  25


then I  would need to plot the following values : 5 - 12  - 8  : i hope
this  make sense

so now how do I configure this in cacti ?
i have a script/command that displays cnt:xxx  delta:yyy
so the script outputs both the value and then calculates the delta by keep
track of the pervious
value in a file...

what I would like is not to have calculate the delta (hundreds of file need
to be kept)

so is this possible with only have the counter vallue?


data template :

Internal Data Source Name  cnt
Minimum Value ('U' for No Minimum) 0
Maximum Value ('U' for No Maximum) 0
Data Source Type counter
Heartbeat  600
Output Field cnt =>  cnt
                   delta =>   delta

(cnt and delta are the words gets displayed by the script)


and the graph template
item 1 : cnt   LINE2 / AVERAGE (from cnt)
item 2 :  av   GPRINT AVERAGE (from cnt)
iitem 3 : cur GPRINT/LAST (from cnt)
item 4 : max GRPINT/MAX (from cnt)

can someone explain what I do wrong? do i really must use the delta i
calculated with the script??

thanks
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