displaymode is a command-line utility for changing the display resolution on Mac OS X. It will work on Mac OS X 10.6 or later.
To change the resolution of the main display to 1440x900, run the command:
./displaymode t 1440 900
To change the resolution of the secondary display to 1440x900, run the command:
./displaymode t 1440 900 1
You can get a list of active displays and available resolutions by running:
./displaymode d
The output will be a table like:
Display 0:
2560 x 1600 @60.0Hz *
1280 x 800 @60.0Hz
2880 x 1800 @60.0Hz
640 x 480 @60.0Hz !
Display 1:
800 x 600 @75.0Hz *
where each row is the width x height in pixels. * indicates the current mode, and ! indicates modes that are not usable for the desktop.
./displaymode h prints a summary of the options.
./displaymode v prints the version and copyright notice.