Question

In emacs, I want to bind a command to C-i. So I put (global-set-key "\C-i" 'forward-word)

in my .emacs file. This works, except now the TAB key is bound to ‘forward-word as well.

How do I bind a command to C-i without changing TAB?

Answer 1

In short, this should solve the problem for you:

(setq local-function-key-map (delq '(kp-tab . [9]) local-function-key-map))
(global-set-key (kbd "C-i") 'forward-word)

Longer version:

From the emacs lisp documentation on function keys:

In ASCII, C-i and <TAB> are the same
character. If the terminal can
distinguish between them, Emacs
conveys the distinction to Lisp
programs by representing the former as
the integer 9, and the latter as the
symbol tab.

Most of the time, it’s not useful to
distinguish the two. So normally
local-function-key-map (see
Translation Keymaps) is set up to map
tab into 9. Thus, a key binding for
character code 9 (the character C-i)
also applies to tab. Likewise for the
other symbols in this group. The
function read-char likewise converts
these events into characters.

So, once you do the following, you can see the difference in the key bindings:

(setq local-function-key-map (delq '(kp-tab . [9]) local-function-key-map))

;; this is C-i
(global-set-key (kbd "C-i") (lambda () (interactive) (message "C-i"))) 
;; this is <tab> key
(global-set-key (kbd "<tab>") (lambda () (interactive) (message "<tab>")))

Note, each mode sets up the various TAB bindings differently, so you may need to do customization per mode that you care about.

Version Dependency:

The above works for Emacs 23.1. From the NEWS file:

Function key sequences are now mapped using `local-function-key-map’,
a new variable. This inherits from the global variable function-key-map,
which is not used directly any more.

Which means, in versions 22 and earlier, you can get the same effect by using the variable function-key-map. I tested this and found it to work with Emacs 21.

(setq local-function-key-map (delq '(kp-tab . [9]) function-key-map))
(global-set-key (kbd "C-i") 'forward-word)