My aim is just to set a maximum of records or entries to that file, that very maximum shall be 200 lines. And I want to extract that specific seven and thirty last entries for that average-value and the sum of each of them. That means the sum of the last seven as well as their average. The same calculation for the last thirty entries.
By now the input is done every time executing the script in the interpreter. It adds one line to the file. This should be done when shutting down the computer, because it is not a server. Therefore the script will be placed in /etc/rc0.d/ with a k-link. And while trying to figure it out it has more than 3400 lines. Yes, I do use root for that purpose. So there is no strange place anyhow for none of the files.
While trying as well the command of "tac" or "sort -nrk5" or similar ones, I want to go on with the upside-down-example given by the user cfajohnson shown in this code snippet below.

Code:

 awk '{x[NR] = $0}
  END { while ( NR > 0 ) print x[NR--] }' /home/uplog.txt;

Assuming to find a solution with NR==1,NR==7 for the range of one calculation e.g.

Code:

 awk '{sum=sum+$5} END {print sum}' /home/uplog.txt

and

Code:

 awk '{sum=sum+$5} END {print sum/NR} /home/uplog.txt

for the average value and the sum of that row.
I suppose this should even work with both targets, the range of
the first seven (after turning it upside down) and the first thirty values. Even in that format of dd/mm/yyyy. So far string4 is shown from position 13 five digits on.
The output so far is the last line of the file, as shown below.

Code:

 24 not yet
sandy
Today is monday  16/06/14 the 25.th Week
99 full 61:52

This output is just adapted to english. But the date-format remains the same dd/mm/yyyy. As in this example the script on this machine has been running 99 times, the 24 (hours) for the user (in this case sandy) are not completed, the date plus the week, 99 lines and the total value.