(lemacs.info)Examining

Examining and Setting Variables
-------------------------------

`C-h v'
`M-x describe-variable'
     Print the value and documentation of a variable.

`M-x set-variable'
     Change the value of a variable.

   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 prints both the value and the
documentation of the variable.

     C-h v fill-column RET

prints something like:

     fill-column's value is 75
     
     Documentation:
     *Column beyond which automatic line-wrapping should happen.
     Automatically becomes local when set in any fashion.

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

   If you know which option you want to set, you can use `M-x
set-variable' to set it.  This prompts for the variable name in the
minibuffer (with completion), and then prompts for 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, as if you had executed the Lisp expression
`(setq fill-column 75)'.

   Setting variables in this way, like all means of customizing Emacs
except where explicitly stated, affects only the current Emacs session.