I know the prompt changes from < to + when the command line in R expects you to complete the current command. Is there a way (say, shortcut key) to immediately terminate the command being written and revert from the '+' mode to the regular console '>'?
Press 'Esc' key will bring you back to the prompt (<). You don't need to type word 'Esc'.
来源：https://stackoverflow.com/questions/22057350/returning-from-the-to-prompt-in-command-line-of-r-studio