How to turn off screen of android with terminal emulator?
There are two ways of doing this, depending on if you have root or not on your device.

If you use root

If you have rooted, run:

su
input keyevent 26


In any good terminal emulator.

If you have not rooted

If you haven't rooted, either root, or:


Install ADB (Instructions vary between windows, Mac and Linux)
Enable "USB Debugging in settings > developer options (if you cannot find developer options, tap the build number in 'about phone' seven times.)
Connect your device to the PC, and connect via ADB
Run: adb shell input keyevent 26