If you want to do the same from the command line, AppleScript makes it straightforward to do from your shell in a single line:

  osascript -e 'tell application "System Events" to tell appearance preferences to get dark mode' # Get current mode
  osascript -e 'tell application "System Events" to tell appearance preferences to set dark mode to true' # Set dark mode
  osascript -e 'tell application "System Events" to tell appearance preferences to set dark mode to false' # Set light mode