(lispref.info)Command Loop Info


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Information from the Command Loop
=================================

   The editor command loop sets several Lisp variables to keep status
records for itself and for commands that are run.

 - Variable: last-command
     This variable records the name of the previous command executed by
     the command loop (the one before the current command).  Normally
     the value is a symbol with a function definition, but this is not
     guaranteed.

     The value is set by copying the value of `this-command' when a
     command returns to the command loop, except when the command
     specifies a prefix argument for the following command.

 - Variable: this-command
     This variable records the name of the command now being executed by
     the editor command loop.  Like `last-command', it is normally a
     symbol with a function definition.

     This variable is set by the command loop just before the command
     is run, and its value is copied into `last-command' when the
     command finishes (unless the command specifies a prefix argument
     for the following command).

     Some commands change the value of this variable during their
     execution, simply as a flag for whatever command runs next.  In
     particular, the functions that kill text set `this-command' to
     `kill-region' so that any kill commands immediately following will
     know to append the killed text to the previous kill.

 - Function: this-command-keys
     This function returns a vector containing the key and mouse events
     that invoked the present command, plus any previous commands that
     generated the prefix argument for this command. (Note: this is not
     the same as in FSF Emacs 19, which can return a string.)  *Note
     Input Events::.

     This function copies the vector and the events; it is safe to keep
     and modify them.

          (this-command-keys)
          ;; Now type `C-u C-x C-e'.
               => [#<keypress-event control-U> #<keypress-event control-X> #<keypress-event control-E>]

 - Variable: last-command-event
     This variable is set to the last input event that was read by the
     command loop as part of a command.  The principal use of this
     variable is in `self-insert-command', which uses it to decide which
     character to insert.

     This variable is off limits: you may not set its value or modify
     the event that is its value, as it is destructively modified by
     `read-key-sequence'.  If you want to keep a pointer to this value,
     you must use `copy-event'.

     Note that this variable is an alias for `last-command-char' in FSF
     Emacs 19.

          last-command-event
          ;; Now type `C-u C-x C-e'.
               => #<keypress-event control-E>

 - Variable: last-command-char
     If the value of `last-command-event' is a keyboard event, then this
     is the nearest ASCII equivalent to it.  This the the value that
     `self-insert-command' will put in the buffer.  Remember that there
     is *not* a 1:1 mapping between keyboard events and ASCII
     characters: the set of keyboard events is much larger, so writing
     code that examines this variable to determine what key has been
     typed is bad practice, unless you are certain that it will be one
     of a small set of characters.

     This function exists for compatibility with Emacs version 18.

          last-command-char
          ;; Now type `C-u C-x C-e'.
               => 5

     The value is 5 because that is the ASCII code for `C-e'.

 - Variable: current-mouse-event
     This variable holds the mouse-button event which invoked this
     command, or `nil'.  This is what `(interactive "e")' returns.

 - Variable: echo-keystrokes
     This variable determines how much time should elapse before command
     characters echo.  Its value must be an integer, which specifies the
     number of seconds to wait before echoing.  If the user types a
     prefix key (say `C-x') and then delays this many seconds before
     continuing, the key `C-x' is echoed in the echo area.  Any
     subsequent characters in the same command will be echoed as well.

     If the value is zero, then command input is not echoed.


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