How do I get just real time value from 'time' command?

I would like 开发者_运维技巧to make a script that outputs only the real time value from the time command so I can plot the results. For example time command outputs

real    1m0.001s
user    1m0.000s
sys  0m0.001s

I want to write a script that outputs

60.001 

How do I get just real time value from 'time' command in seconds?

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If you're using the Bash builtin time, set the TIMEFORMAT variable to %R:

$ TIMEFORMAT=%R
$ time sleep 1
1.022

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time can take an optional --format or -f parameter, but you have to use the full path to the time command, /usr/bin/time

/usr/bin/time -f "%e" sleep 3

3.00

Without the path, it'll use the time command of the shell which just treats all arguments as the command, so you'll get an -f: command not found.

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If you write \time you enforce not to use the bash built in time. So with \time -f '%e' command you are done.

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Alternatively, use /usr/bin/time or take a look at the similar question
Using time command in bash script.