If you run or write a lot of software run on the command line from time to time you probably want to know how long something you ran took to run. What’s great about the time command is all you need to do to use it is throw it in front of whatever you were already running.
Here are a few examples
How long does it take to download a url
time curl -s 'http://www.google.com' > /dev/null
Time your python script runtime
time python your_cool_script.py
real – the wall clock time it took a process to complete, or how long it took to run.
user – number of cpu seconds the process used directly.
sys – number of cpu seconds the kernel used on behalf of the process.