Question

I found partial solutions on several sites, so I pulled several parts together, but I still couldn’t figure it out.

Here is what I am doing:

I am running a simple java program from Terminal, and need to find the average runtime for the program.

What I am doing is running the command several times, finding the total time, and then dividing that total time by the number of times I ran the program.

I would also like to acquire the output of the program rather than displaying it on standard output.

Here is my current code and the output.

Shell Script:

   startTime=$(date +%s%N)
   for ((i = 0; i <  $runTimes; i++))
   do
            java Program test.txt > /dev/null
   done
   endTime=$(date +%s%N)
   timeDiff=$(( $endTime - $startTime ))
   timeAvg=$(( $timeDiff / $numTimes ))
   echo "Avg Time Taken: "
   echo $timeAvg

Output:

 ./run: line 12: 1305249784N: value too great for base (error token is "1305249784N")

The line number 12 is off because this code is part of a larger file.
The line number 12 is the line with timeDiff being evaluated.

I appreciate any help, and apologize if this question is redundant or off-topic.

Answer 1

On my machine, I don’t see what the %N format for date is getting you, as the value seems to be 7 zeros, BUT it is making a much bigger number to evaluate in the math, i.e. 1305250833570000000. Do you really need nano-second precision? I’ll bet if you go with just %s it will be fine.

Otherwise you look to be on the right track.

P.S.

Oh yeah, minor point,

 echo "Avg Time Taken:  $timeAvg" 

Is a a simpler way to achieve your required output 😉

Option 2. You could take out the date calculations all together, and turn your loop into a small script. Then you can use a built-in feature of the shell

time myJavaTest.sh

Will give you details like

real    0m0.049s
user    0m0.016s
sys     0m0.015s

I hope this helps.