How to output the real time a command takes (and nothing else)?

Question

How can I output the real time a command takes (and nothing else)?

Example:

This won't work:

$ time -p sleep 2 | grep real
real 2.00
user 0.00
sys 0.00

I want something like:

$ print-real-time sleep 2
2.00

score 5 · Accepted Answer · answered Sep 29 '11 at 18:20

5

You need to capture the output of time first. Then you can process it.

answered Sep 29 '11 at 18:20

Right. The question is how to do that... – user9474 Sep 29 '11 at 18:22
3

Did you bother read the linked article? – Ignacio Vazquez-Abrams Sep 29 '11 at 18:24
Oh, I didn't see it was a link. Thanks! – user9474 Sep 29 '11 at 18:26
1

Good solution, note however that the entire world is not running bash... – voretaq7 Sep 29 '11 at 18:27

score 3 · Answer 2 · edited Sep 30 '11 at 16:39

3

A non-BASH-specific solution (explicitly use /usr/bin/time so it's not the pipe-gobbling bash builtin) --

/usr/bin/time -p some_command_or_subshell 2>&1 | grep real | awk '{print $2}'

Depending on the delicate nature of whatever you feed this output to you may want to redirect the output of your subject command to /dev/null...

edited Sep 30 '11 at 16:39

Shane Madden

answered Sep 29 '11 at 18:31

voretaq7

score 0 · Answer 3 · answered Sep 29 '11 at 18:33

0

Here's a hacky solution using cut to split the fields.

time -p sleep 2 | grep real | cut -f2 -d' '

You can also use awk:

time -p sleep 2 | grep real | awk '{ print $2 }'

answered Sep 29 '11 at 18:33

Andrew M.

Does that actually work on your system? On mine, it doesn't give the desired output "2.00". – user9474 Sep 29 '11 at 19:12
It works on mine; but it probably also depends on what `time` command you're running. It sounds like bash behaves differently with this--zsh gives you the output on stdout normally. – Andrew M. Sep 30 '11 at 13:33
@Redmumba this is the principle danger of using shell builtins - they may not work the same way for everyone, and in your case they don't conform to the POSIX standard ( `time` is *supposed* to report its output to `stderr`, not `stdout` ; cf. http://pubs.opengroup.org/onlinepubs/9699919799/utilities/time.html ) – voretaq7 Sep 30 '11 at 16:29
Tres bizarre! I guess you learn something new everyday. – Andrew M. Sep 30 '11 at 18:57

3 Answers3