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I am trying to get the time it takes to run a command, with the output in a specific format:

time -f "%E" ls -l

This is similar to the example in the man page (and on the online man page). However when I run this command I get:

-f: command not found

It appears as though the time command is not reading the -f as an argument, rather as the command I am trying to run.

How can I get the execution time for a command in a specific format?

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up vote 10 down vote accepted

This is because time is a bash builtin command - and the builtin doesn't support the options you're trying to use.

Try this, use the full path of time to skip the built-in and use the real one:

/usr/bin/time -f "%E" ls -l
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ah ha! Tricky, tricky. That does it, thanks. – Isaac Dec 8 '11 at 16:55

Unfortunately, time is both a bash keyword and a program in /usr/bin. If you specify the full path to time, as in /usr/bin/time -f "%E" ls -l you will get the output you were expecting.

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