/usr/bin/time: not the command you think you know

Re:/usr/bin/time: not the command you think you know by jcoffland on Tuesday March 07, 2017 @02:16AM (#13808814)

Run these commands for a better demonstration:

    time echo | sleep 1

vs.

    /usr/bin/time echo | sleep 1

The former times the entire pipeline whereas the later only times the first command in the pipe.

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Re:/usr/bin/time: not the command you think you know by fnord123 on Tuesday March 07, 2017 @05:09AM (#13809386)

This also gives the time of the entire pipeline (since the commands all begin together and only finish when the last command has completed):

echo | /usr/bin/time sleep 1

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Re:/usr/bin/time: not the command you think you know by roblabla on Tuesday March 07, 2017 @07:31AM (#13809850)

I'm pretty sure this is wrong.

As an example :

sleep 2 | /usr/bin/time sleep 1

This gives an output of "1 second" even though the entire pipeline took 2 seconds.

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Re:/usr/bin/time: not the command you think you know by fnord123 on Tuesday March 07, 2017 @08:15AM (#13810037)

Ok you can wangle your way out of it. But if you're doing something like `grep "$something" | /usr/bin/time some_job` then generally you're fine.

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Re:/usr/bin/time: not the command you think you know by perennate on Tuesday March 07, 2017 @08:46AM (#13810227)

Wouldn't the system/user time be wrong though?

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Re:/usr/bin/time: not the command you think you know by exprA on Tuesday March 07, 2017 @08:06AM (#13809997)

The sleep sub-process of time is not part of the pipeline, however. It will exit after the requested time has passed.

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