How do I set the Emacs fill-column for a specific mode?

Question

I would like to set the fill-column in Emacs to 120 for Clojure-mode, but leave it at the default (80) otherwise.

How can I do this in my .emacs file?

Thanks.

Answer 1

Add a call to set-fill-column to the clojure-mode-hook.

(add-hook 'clojure-mode-hook
          (lambda ()
            (set-fill-column 120)))

As fill-column is buffer local, it won't affect other buffers. In fact, you can invoke M-x set-fill-column RET 120 to set the fill column in any Emacs buffer interactively.

You can check if a variable is buffer local by invoking the help: C-h v fill-column specifies:

Automatically becomes buffer-local when set in any fashion.

Answer 2

fill-column is a buffer-local variable, i.e. it can have unique value in each buffer (if you want). So you can just set it in clojure-mode hook.