How can I know my L4T verion is R19 or R21?

Autonomous Machines Jetson & Embedded Systems Legacy Tegra Platforms (T20-T40)
#1

Many thanks!

#2

Please don’t start multiple threads about the same problem.

Continuing here: https://devtalk.nvidia.com/default/topic/820471/embedded-systems/how-can-i-know-my-l4t-verion-is-r19-or-r21-/