57.3.1 Examining and Setting Variables
- C-h v var <RET>
- Display the value and documentation of variable var
- 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 70
*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 variable 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 (you can insert the old
value into the minibuffer for editing via M-n). For example,
M-x set-variable <RET> fill-column <RET> 75 <RET>
fill-column to 75.
M-x set-variable is limited to user option variables, but you can
set any variable with a Lisp expression, using the function
Here is a
setq expression to set
(setq fill-column 75)
To execute an expression like this one, go to the ‘*scratch*’
buffer, type in the expression, and then type C-j. See Lisp Interaction.
Setting variables, like all means of customizing Emacs except where
otherwise stated, affects only the current Emacs session. The only
way to alter the variable in future sessions is to put something in
the ~/.emacs file to set it those sessions (see Init File).