Next: Defining Commands, Up: Command Loop
The first thing the command loop must do is read a key sequence, which
is a sequence of events that translates into a command. It does this by
calling the function read-key-sequence. Your Lisp code can also
call this function (see Key Sequence Input). Lisp programs can also
do input at a lower level with read-event (see Reading One Event) or discard pending input with discard-input
(see Event Input Misc).
The key sequence is translated into a command through the currently
active keymaps. See Key Lookup, for information on how this is done.
The result should be a keyboard macro or an interactively callable
function. If the key is M-x, then it reads the name of another
command, which it then calls. This is done by the command
execute-extended-command (see Interactive Call).
To execute a command requires first reading the arguments for it.
This is done by calling command-execute (see Interactive Call). For commands written in Lisp, the interactive
specification says how to read the arguments. This may use the prefix
argument (see Prefix Command Arguments) or may read with prompting
in the minibuffer (see Minibuffers). For example, the command
find-file has an interactive specification which says to
read a file name using the minibuffer. The command's function body does
not use the minibuffer; if you call this command from Lisp code as a
function, you must supply the file name string as an ordinary Lisp
function argument.
If the command is a string or vector (i.e., a keyboard macro) then
execute-kbd-macro is used to execute it. You can call this
function yourself (see Keyboard Macros).
To terminate the execution of a running command, type C-g. This character causes quitting (see Quitting).
The editor command loop runs this normal hook before each command. At that time,
this-commandcontains the command that is about to run, andlast-commanddescribes the previous command. See Command Loop Info.
The editor command loop runs this normal hook after each command (including commands terminated prematurely by quitting or by errors), and also when the command loop is first entered. At that time,
this-commandrefers to the command that just ran, andlast-commandrefers to the command before that.
Quitting is suppressed while running pre-command-hook and
post-command-hook. If an error happens while executing one of
these hooks, it terminates execution of the hook, and clears the hook
variable to nil so as to prevent an infinite loop of errors.
A request coming into the Emacs server (see Emacs Server↗) runs these two hooks just as a keyboard command does.