time

If you read time(1) man page, you'll see that :
* the "real" time is the elapsed (wall clock) time used by the process
* the "user" time is the total number of CPU-seconds that the process used directly (in user mode)
* the "system" time is the total number of CPU-seconds used by the system on behalf of the process (in kernel mode)

To compare your scripts speed, I think "user"+"sys" is a good choice, "real" time can (should) be more than the sum of these two, because it includes time spent running and attending other processes.

And remember, "man" is our friend ;-)

http://www.experts-exchange.com/OS/Linux/Q_21104267.html