You don't need 5 posts to cut and paste sample data into a post (just like you did with your code). It looks like you're saying you have a file (in a very strange place unless you're running as root) that contains lines like:

Code:

uptime username an   ays,   MM/DD/YYYY
uptime username an   days,   MM/DD/YYYY
            or
uptime username an   N day   MM/DD/YYYY

depending on how long many days the machine has been up (where username, MM, DD, and YYYY are obvious and N is the last digit in the number of days the system has been running if the system has been up for more than 999 days). (Of course, your version of uptime may print something else in the 5 characters starting in position 15.)

And, this would mean the output from awk could be something like:

Code:

325 full 506/15/2014
       or
325 full 6day

assuming you had collected 324 samples before you ran the script and that awk saw the last sample you added to the log using echo and head.
Note that the head in this script is a fairly expensive no-op. And, the awk can be replaced by a set and an echo.

I repeat. Please tell us in English what you are trying to do!
Show us sample input!
Show us desired output!

Keeping only the last 200 lines in your log file can be done by:

Code:

(tail -n 199 /home/uplog.txt
echo "uptime" $USER "an" $machine " " ${string4:13:5} " " ${string5}) > newuplog.txt && mv newuplog.txt /home/uplog.txt

(assuming that you are running this in a directory that is on the same filesystem as /home).

If this is code being run by a normal user, I would have expected it to use $HOME/uplog.txt rather than /home/uplog.txt.

How is capturing 7 or 30 copies of the word day possibly mixed with dates of the form MM/DD/YYYY going to help you calculate average or total uptime? This makes no sense to me. PLEASE SHOW US SAMPLE DATA!