emacs: M-x
9 Running Commands by Name
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Every Emacs command has a name that you can use to run it. For
convenience, many commands also have key bindings. You can run those
commands by typing the keys, or run them by name. Most Emacs commands
have no key bindings, so the only way to run them is by name. (
Key Bindings, for how to set up key bindings.)
By convention, a command name consists of one or more words,
separated by hyphens; for example, ‘auto-fill-mode’ or ‘manual-entry’.
Command names mostly use complete English words to make them easier to
remember.
To run a command by name, start with ‘M-x’, type the command name,
then terminate it with <RET>. ‘M-x’ uses the minibuffer to read the
command name. The string ‘M-x’ appears at the beginning of the
minibuffer as a “prompt” to remind you to enter a command name to be
run. <RET> exits the minibuffer and runs the command.
Minibuffer, for more information on the minibuffer.
You can use completion to enter the command name. For example, to
invoke the command ‘forward-char’, you can type
M-x forward-char <RET>
or
M-x forw <TAB> c <RET>
Note that ‘forward-char’ is the same command that you invoke with the
key ‘C-f’. The existence of a key binding does not stop you from
running the command by name.
When ‘M-x’ completes on commands, it ignores the commands that are
declared “obsolete”; for these, you will have to type their full name.
Obsolete commands are those for which newer, better alternatives exist,
and which are slated for removal in some future Emacs release.
To cancel the ‘M-x’ and not run a command, type ‘C-g’ instead of
entering the command name. This takes you back to command level.
To pass a numeric argument to the command you are invoking with
‘M-x’, specify the numeric argument before ‘M-x’. The argument value
appears in the prompt while the command name is being read, and finally
‘M-x’ passes the argument to that command.
When the command you run with ‘M-x’ has a key binding, Emacs mentions
this in the echo area after running the command. For example, if you
type ‘M-x forward-word’, the message says that you can run the same
command by typing ‘M-f’. You can turn off these messages by setting the
variable ‘suggest-key-bindings’ to ‘nil’. The value of
‘suggest-key-bindings’ can also be a number, in which case Emacs will
show the binding for that many seconds before removing it from display.
The default behavior is to display the binding for 2 seconds.
Commands that don’t have key bindings, can still be invoked after
typing less than their full name at the ‘M-x’ prompt. Emacs mentions
such shorthands in the echo area if they are significantly shorter than
the full command name. The setting of ‘suggest-key-bindings’ affects
these hints as well.
In this manual, when we speak of running a command by name, we often
omit the <RET> that terminates the name. Thus we might say ‘M-x
auto-fill-mode’ rather than ‘M-x auto-fill-mode <RET>’. We mention the
<RET> only for emphasis, such as when the command is followed by
arguments.
‘M-x’ works by running the command ‘execute-extended-command’, which
is responsible for reading the name of another command and invoking it.
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