If you want to test the time it takes to run a script, you can use the UNIX ‘time’ command. the manual page states:
The time utility executes and times the specified utility. After the utility finishes, time writes to the standard error stream, (in seconds): the total time elapsed, the time used to execute the utility process and the time consumed by system overhead.
see this example:
# time /bin/rehash real 0m0.007s user 0m0.007s sys 0m0.000s