Emacs global-set-key to C-TAB

Question

I'm trying to set a key-binding to Ctrl+TAB in Emacs. I used the following call:

(global-set-key (read-kbd-macro "C-TAB") 'my-func)

However, whenever I use it, I get a

<C-tab> is undefined

error message. Trying to set the binding to "C-tab" results in an error message.

How can I set my binding to C-TAB?

Answer 1

Unlike others have suggested, it is a good idea to use kbd (or read-kbd-macro which is basically the same thing) in case you ever want to use the same configuration files in other versions of Emacs; kbd works across several versions of Emacs and XEmacs, where the internal representation of key sequences are different.

(global-set-key (kbd "<C-tab>") 'my-func)

The input format used by read-kbd-macro is documented in the docstring of edmacro-mode:

• The special words RET, SPC, TAB, DEL, LFD, ESC, and NUL represent special control characters. The words must be written in uppercase.

• A word in angle brackets, e.g., <return>, <down>, or <f1>, represents a function key. (Note that in the standard configuration, the function key <return> and the control key RET are synonymous.) You can use angle brackets on the words RET, SPC, etc., but they are not required there.

This is written somewhat unfortunately; the TAB referred to in the first bullet point is the ASCII character for TAB, and adding the Control modifier does something nonsensical to it. When you press Control-Tab, Emacs sees it (via your windowing system; it will not work in a text terminal) as <tab> with a Control modifier, which you can represent as C-<tab> or <C-tab>.

Answer 2

(global-set-key [C-tab] 'my-func)