I am trying to run as root user :: cat /dev/graphics/fb0 in my android (oreo) phone. But showing 'No such device' error. Could anyone guide me on how to make

I am trying to run as root user :: cat /dev/graphics/fb0 in my android (oreo) phone. But showing 'No such device' error. Could anyone guide me on how to make it work so that I could take screenshot directly and do some graphics stuff on my phone directly.