10.1.2 Mode Hooks

Every major mode, apart from ‘Fundamental’ mode, defines a mode hook, a customizable list of Lisp functions to run each time the mode is enabled in a buffer.

Each mode hook is named after its major mode, e.g., Fortran mode has fortran-mode-hook. Furthermore, all text-based major modes run text-mode-hook, and many programming language modes (including all those distributed with Emacs) run prog-mode-hook, prior to running their own mode hooks. Hook functions can look at the value of the variable major-mode to see which mode is actually being entered.

Mode hooks are commonly used to enable minor modes. For example, you can put the following lines in your init file to enable ‘Flyspell’ minor mode in all text-based major modes (see Spelling), and ‘ElDoc’ minor mode in Emacs Lisp mode (see Lisp Doc):

(add-hook 'text-mode-hook 'flyspell-mode)
(add-hook 'emacs-lisp-mode-hook 'eldoc-mode)