A command-line utility to programmatically adjust the brightness of displays on Mac OS X. Brightness is adjustable in this way only on certain displays, typically the built-in displays of Macs.
Personally I find this useful when used together with display calibration - a simple script can restore the display to the brightness setting used to calibrate colours, allowing me to make rough adjustments via keyboard commands (e.g., when playing games or watching movies) without worrying about being able to go back to the calibrated setting.
There are other utilities for this, but most of them seem to use the
CGDisplayIOServicePort() function, which is deprecated as of OS X 10.9,
and/or they do not support display names.
~ Kimmo Kulovesi, 2014-07-18
The default behaviour of brightness is to list all displays and
their brightness values. Specifying a brightness (typically a number
from 0.0 to 1.0) on the command-line sets the brightness of all
applicable displays to that number. The option -d display can be used
to name a specific display to adjust.
Example to set the display named iMac to brightness 0.5 (50%):
brightness -d iMac 0.5
Run the program with the argument -h for help, or see the included
man page.