How can I get the current screen resolution from the command line on OS X?

system_profiler SPDisplaysDataType | grep Resolution

For a quick reading on the current virtual resolution of a single retina display:

$ osascript -e 'tell application "Finder" to get bounds of window of desktop'
0, 0, 2048, 1280

Results for multi-monitor setups vary based on which display is primary and how they are arranged. Read more here

I use the utility screenresolution to get the screen resolution:

$ /usr/local/bin/screenresolution get 2>&1 | grep -oE 'Display 0: [0-9]+' | grep -Eo '[0-9]+$'  
1920