7 Running Commands by Name
The Emacs commands that are used often or that must be quick to type are
bound to keys--short sequences of characters--for convenient use. Other
Emacs commands that are used more rarely are not bound to keys; to run
them, you must refer to them by name.
A command name consists, by convention, of one or more words,
separated by hyphens: for example, `auto-fill-mode' or `manual-entry'.
The use of English words makes the command name easier to remember than
a key made up of obscure characters, even though it results in more
characters to type. You can run any command by name, even if it can be
run by keys as well.
To run a command by name, start with `M-x', then type the command
name, and finish with <RET>. `M-x' uses the minibuffer to read the
command name. <RET> exits the minibuffer and runs the command.
Emacs uses the minibuffer for reading input for many different
purposes; on this occasion, the string `M-x' is displayed at the
beginning of the minibuffer as a "prompt" to remind you that your input
should be the name of a command to be run. Note: Minibuffer, for
full information on the features of the minibuffer.
You can use completion to enter a command name. For example, to
invoke the command `forward-char', type:
M-x forward-char <RET>
M-x fo <TAB> c <RET>
After you type in `M-x fo TAB' emacs will give you a possible list of
completions from which you can choose. Note that `forward-char' is the
same command that you invoke with the key `C-f'. You can call any
command (interactively callable function) defined in Emacs by its name
using `M-x' regardless of whether or not any keys are bound to it.
If you type `C-g' while Emacs reads the command name, you cancel the
`M-x' command and get out of the minibuffer, ending up at top level.
To pass a numeric argument to a command you are invoking with `M-x',
specify the numeric argument before the `M-x'. `M-x' passes the
argument along to the function that it calls. The argument value
appears in the prompt while the command name is being read.
You can use the command `M-x interactive' to specify a way of
parsing arguments for interactive use of a function. For example,
(defun foo (arg) "Doc string" (interactive "p") ...use arg...)
to make `arg' be the prefix argument when `foo' is called as a
command. The call to `interactive' is actually a declaration rather
than a function; it tells `call-interactively' how to read arguments to
pass to the function. When actually called, `interactive' returns
The argument of INTERACTIVE is usually a string containing a code
letter followed by a prompt. Some code letters do not use I/O to get
the argument and do not need prompts. To prompt for multiple arguments,
you must provide a code letter, its prompt, a newline, and another code
letter, and so forth. If the argument is not a string, it is evaluated
to get a list of arguments to pass to the function. If you do not
provide an argument to `interactive', no arguments are passed when
Available code letters are:
Function name: symbol with a function definition
Name of existing buffer
Name of buffer, possibly nonexistent
Command name: symbol with interactive function definition
Value of point as number (does not do I/O)
Last mouse event
Existing file name
Possibly nonexistent file name
Key sequence (string)
Value of mark as number (does not do I/O)
Number read using minibuffer
Prefix arg converted to number, or if none, do like code `n'
Prefix arg converted to number (does not do I/O)
Prefix arg in raw form (does not do I/O)
Region: point and mark as two numeric arguments, smallest first
(does not do I/O)
Variable name: symbol that is `user-variable-p'
Lisp expression read but not evaluated
Lisp expression read and evaluated
In addition, if the string begins with `*', an error is signaled if
the buffer is read-only. This happens before reading any arguments.
If the string begins with `@', the window the mouse is over is selected
before anything else is done. You may use both `@' and `*'; they are
processed in the order that they appear.
Normally, when describing a command that is run by name, we omit the
<RET> that is needed to terminate the name. Thus we may refer to `M-x
auto-fill-mode' rather than `M-x auto-fill-mode' <RET>. We mention the
<RET> only when it is necessary to emphasize its presence, for example,
when describing a sequence of input that contains a command name and
arguments that follow it.
`M-x' is defined to run the command `execute-extended-command',
which is responsible for reading the name of another command and
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