Get program execution time in the shell

Question

I want to execute something in a Linux shell under a few different conditions and be able to output the execution time of each execution.

I know I could write a Perl or python script that would do this, but is there a way I can do it in the shell?

Answer 1

Use the built-in time keyword:

$ help time

The time: time [-p] PIPELINE executes PIPELINE and prints a summary of the real-time, user CPU time and system CPU time spent executing PIPELINE when it terminates. The return status is the return status of PIPELINE.  The `-p' option prints the timing summary in a slightly different format. This uses the value of the TIMEFORMAT variable as the output format.

Example:

$ time sleep 2

real    0m2.009s

user    0m0.000s

sys     0m0.004s