active_gfx shows the graphics card currently in use by you macOS system. This tool is helpful if you want to monitor the usage of your discrete graphics card. Your MacBook Pro will use much more power, if it uses the discrete graphics card, so keeping an eye on it is wise while running on battery.
Instead of going through the list of open processes in Activity Monitor, this tool spits out the currently used graphics chip by querying the system_profiler.
active_gfx is a ruby gem, so install via gem install active_gfx.
Usage: active_gfx [options]
-a, --all Shows all graphics chips instead of only in use
-p, --pretty Print the pretty name of graphics card instead of model identifier
-h, --help Prints this help
-v, --version Show version
% active_gfx
# => kHW_IntelHDGraphics530Item
% active_gfx --pretty
# => Intel HD Graphics 530