Examining and Setting Variables

C-h v var RET

Display the value and documentation of variable var (describe-variable).

M-x set-variable RET var RET value RET

Change the value of variable var to value.

To examine the value of a single variable, use C-h v (describe-variable), which reads a variable name using the minibuffer, with completion. It displays both the value and the documentation of the variable. For example,

C-h v fill-column RET

displays something like this:

fill-column's value is 75

Documentation:
*Column beyond which automatic line-wrapping should happen.
Automatically becomes buffer-local when set in any fashion.

The star at the beginning of the documentation indicates that this variable is a user option. C-h v is not restricted to user options; it allows any variable name.

The most convenient way to set a specific user option is with M-x set-variable. This reads the variable name with the minibuffer (with completion), and then reads a Lisp expression for the new value using the minibuffer a second time. For example,

M-x set-variable RET fill-column RET 75 RET

sets fill-column to 75.

M-x set-variable is limited to user option variables. You can set any variable with a Lisp expression using the function setq. Here's how to use it to set fill-column:

(setq fill-column 75)

Setting variables, like all means of customizing Emacs except where otherwise stated, affects only the current Emacs session.