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? (which happens to be bash)

Answer 1

Use the built-in time keyword:

$ help time

time: time [-p] PIPELINE
    Execute PIPELINE and print 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

Answer 2

The way is

$ > g++ -lpthread perform.c -o per
$ > time ./per

output is >>

real    0m0.014s
user    0m0.010s
sys     0m0.002s

Answer 3

For a line-by-line delta measurement, try gnomon.

A command line utility, a bit like moreutils's ts, to prepend timestamp information to the standard output of another command. Useful for long-running processes where you'd like a historical record of what's taking so long.

You can also use the --high and/or --medium options to specify a length threshold in seconds, over which gnomon will highlight the timestamp in red or yellow. And you can do a few other things, too.

Answer 4

You can use time and subshell ():

time (
  for (( i=1; i<10000; i++ )); do
    echo 1 >/dev/null
  done
)

Or in same shell {}:

time {
  for (( i=1; i<10000; i++ )); do
    echo 1 >/dev/null
  done
}