Merge branch 'master' of github.com:khanhicetea/today-i-learned

Author: khanhicetea

sysadmin/time-command-output-meaning.md

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+- Date : 2017-10-04
+- Tags : #sysadmin #cpu #time
+
+## TIME command output meaning
+
+When you want to know how long does it take to run a process, just use `time` command as a prefix
+
+```bash
+$ time my_program arg1 arg2
+real        0m0.003s
+user        0m0.000s
+sys         0m0.004s
+```
+
+- **real** : wall clock time, mean time to start to finish your process
+- **user** : CPUs-time outside the kernel
+- **sys** : CPUs-time within the kernel
+
+**real+sys** result is total multi CPUs time (so if you have a multi core CPUs, it is often bigger than **real**)
+