Info Catalog emacs: Variables emacs: Hooks

emacs: Examining

 
 51.2.1 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 variable, use ‘C-h v’
 (‘describe-variable’).  This reads a variable name using the minibuffer,
 with completion, and displays both the value and the documentation of
 the variable.  For example,
 
      C-h v fill-column <RET>
 
 displays something like this:
 
      fill-column is a variable defined in ‘C source code’.
      Its value is 70
 
        Automatically becomes buffer-local when set.
        This variable is safe as a file local variable if its value
        satisfies the predicate ‘integerp’.
 
      Documentation:
      Column beyond which automatic line-wrapping should happen.
      Interactively, you can set the buffer local value using C-x f.
 
      You can customize this variable.
 
 The line that says ‘You can customize the variable’ indicates that this
 variable is a user option.  ‘C-h v’ is not restricted to user options;
 it allows non-customizable variables too.
 
    The most convenient way to set a specific customizable 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>
 
 sets ‘fill-column’ to 75.
 
    ‘M-x set-variable’ is limited to customizable variables, but you can
 set any variable with a Lisp expression like this:
 
      (setq fill-column 75)
 
 To execute such an expression, type ‘M-:’ (‘eval-expression’) and enter
 the expression in the minibuffer (Lisp Eval).  Alternatively, go
 to the ‘*scratch*’ buffer, type in the expression, and then type ‘C-j’
 (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 your
 initialization file (Init File).
 

Info Catalog emacs: Variables emacs: Hooks