Power off frozen Macbook with a touch-bar I have a MacBook Pro with a touch-bar, and thus no physical power button. 


I have tried holding my finger on the touch id button, but to no avail. 
It has been frozen for several hours (on the screen of just apple symbol with loading bar) while updating
I want to try to power it off/power it back on again to try to unfreeze it. 


Is there some keystroke or button that can power it off?
The TouchBar mac with Touch ID sensor is a physical power switch, so pressing and holding it will shut down the machine as long as two things are true:


The button physically registers your push.
The SMC is listening and will initiate the power shutdown.




https://support.apple.com/en-us/HT201150

Barring those, if you press for 20 seconds gently yet firmly, you may have to wait for the battery to discharge and then charge. Watch your backup in case the machine needs hardware service or a reset of the SMC / restore or revive of the T2/SMC.