Choosing an escape key for screen and tmux
Usually I don’t like to change the default terminal configuration because it becomes impossible to use someone else’s computer or for them to use yours.
However, the default choices of C-a in screen and C-b in tmux are awful if you’re used to emacs-style text navigation.
I have been using C-] for a few years and I’m pretty happy with it.
I wanted to document the reasoning behind this choice.
The criteria for an escape key are:
- it should not be a shortcut that you need to use often,
- it should not have dramatic consequences outside of screen and
- it should be easy to type (single modifier key).
Here is an evaluation of all 32 ASCII control characters in order.
| Key | Code | Rating | Reason |
|---|---|---|---|
C-SPC |
0 | no | emacs (set mark) |
C-a |
1 | no | emacs (start of line) |
C-b |
2 | no | emacs (move cursor back) |
C-c |
3 | no | bash (sends SIGINT) |
C-d |
4 | no | end of transmission, exit shell; vim (page down) |
C-e |
5 | no | emacs (end of line) |
C-f |
6 | no | emacs (move cursor forward) |
C-g |
7 | no | emacs (abort command) |
C-h |
8 | no | backspace key; emacs (help prefix) |
C-i |
9 | no | tab key \t; vim (move cursor to next position in history) |
C-j |
10 | no | line feed \n; emacs (evaluate lisp expression) |
C-k |
11 | no | emacs (kill to end of line) |
C-l |
12 | no | bash (clear screen); emacs (scroll such that current line is at top/middle/bottom) |
C-m |
13 | no | return \r |
C-n |
14 | no | emacs (next line) |
C-o |
15 | no | vim (move cursor to previous position in history) |
C-p |
16 | no | emacs (previous line) |
C-q |
17 | maybe | emacs (quoted insert; toggle read-only status) |
C-r |
18 | no | vim (redo); shell (reverse search) |
C-s |
19 | no | emacs (save current file) |
C-t |
20 | maybe | emacs (transpose characters/lines) |
C-u |
21 | no | bash (kill to start of line); vim (page up) |
C-v |
22 | no | emacs (page down); vim (block-selection mode; insert control key) |
C-w |
23 | no | emacs (kill region); bash (kill previous word); vimdiff (switch panes) |
C-x |
24 | no | emacs (start of key sequence) |
C-y |
25 | no | emacs (yank) |
C-z |
26 | maybe | bash (sends SIGSTOP) |
C-[ |
27 | no | escape key (prohibitive for vim) |
C-\ |
28 | no | bash (sends SIGQUIT) |
C-] |
29 | yes | |
C-^ |
30 | no | no easy way to type? |
C-/ |
31 | no | emacs (redo) |
C-- |
31 | no | equal to C-/ |
Note that the key combinations C-;, C-', C-., C-, and C-= do not correspond to control characters.
Just be careful; C-] can be right next to C-\, which sends SIGQUIT.
Update (Nov 2021): Thanks to Jay Freeman for pointing out that C-] is used to jump to a tag in vim.