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

Question

I would like 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

Answer 1

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.