Time command

$ time ls
real    0m0.005s
user    0m0.004s
sys    0m0.000s

        * The elapsed (real) time between invocation of utility and its
termination.

* The User CPU time, equivalent to the sum of the tms_utime and
tms_cutime fields returned by the times() function defined in the
System Interfaces volume of IEEE Std 1003.1-2001 for the process in
which utility is executed.

* The System CPU time, equivalent to the sum of the tms_stime and
tms_cstime fields returned by the times() function for the process
in which utility is executed.

ที่มา: Time