Terminal – Control and Up/Down Keys for Emacs

emacskeyboardterminal

Is it possible to use C-up and C-down when running emacs in the terminal window (when starting emacs from the command line with the -nw flag)? What should my terminal send when I press C-up and C-down for these keys to work in emacs?

I'm on Mac OSX, using iterm2 to ssh into a remote linux server, where I start the emacs session from bash.

Best Answer

Terminals know characters, not keys, so keys with no corresponding character need to be translated into escape sequences and back.

You can pick any control sequences that doesn't cause any conflict and that iterm2 and Emacs agree on. Unfortunately, these control sequences aren't standardized. \e[1;5A and \e[1;5B are popular choices (where \e is an escape character).

Emacs has a fairly complex system to translate escape sequences into keys. See translation keymaps in the manual. Use input-decode-map unless you have an old version of Emacs that doesn't have it.

(define-key input-decode-map "\e[1;5A" [C-up])
(define-key input-decode-map "\e[1;5B" [C-down])

In iterm2, set the corresponding key sequences in the “Keys” tab in your profile. See How can I get control+left arrow to go back one word in iTerm2? for an illustrated guide.

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I think you want to determine if a command is run in a terminal.

if [ -t 2 ]; then
  # Standard error is a terminal
  emacs -nw "$@"
elif [ -n "$DISPLAY" ]; then
  # An X display is available
  xterm -e emacs -nw "$@"
else
  # We have nothing
  emacs --daemon "$@"
fi

If you want this to always happen when you run Emacs, put it in a script and invoke that script instead. You can call the script /usr/local/bin/emacs (assuming Linux) if you want it to be called emacs and invoked in preference to the “real” emacs executable in /usr/bin.

Note that to edit files as root, you should use sudoedit (benefits: the editor runs as you so you get all your settings; the edited file is put into place atomically when you finish editing, reducing the chance of a mishap). You can also edit files as root directly inside Emacs by opening /sudo::/path/to/file.

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The value of the TERM environment variable should be the same on both systems.

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