[mrtg] Merging/Combining log files

[Alex van den Bogaerdt]

Questions on merging log files after a change has occured.
How to combine the two logfiles so that you end up with a
logfile containing useful information both from the present
and from the past.

It isn't that hard:

1) Get the two files in sync (same last update time, the 3rd line and
   further should have the same time stamps)
2) Get the interesting part of the new log file (the updated stuf)
3) Get the interesting part of the old log file (historic data)
4) Combine them

In ascii-art:
           new     old
          +---+   +---+
     now  | A |   | D |
          |   |   |   |
           ...     ...
  change  | B |   | E |
           ...     ...
          |   |   |   |
way back  | C |   | F |
          +---+   +---+

B and E are the row with the time stamp where your change occured.
A and D are after the change
C and F are before the change

A,B and F contain information
C,D and E is not interesting

You want to combine the new file with historic data from the old file:

           new  +  old  -> combined
          +---+   +---+    +---+
     now  | A |   | D |    | A |
          |   |   |   |    |   |
           ...     ...      ...
  change  | B |   | E |    | B |
           ...     ...      ...
          |   |   |   |    |   |
way back  | C |   | F |    | F |
          +---+   +---+    +---+

HTH
Alex
-- 
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