@c This is part of the Emacs manual.
@c Copyright (C) 1985--1987, 1993--1995, 1997, 2001--2022 Free Software
@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node M-x
@chapter Running Commands by Name

  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.
(@xref{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, @code{auto-fill-mode} or
@code{manual-entry}.  Command names mostly use complete English words
to make them easier to remember.

@kindex M-x
  To run a command by name, start with @kbd{M-x}, type the command
name, then terminate it with @key{RET}.  @kbd{M-x} uses the minibuffer
to read the command name.  The string @samp{M-x} appears at the
beginning of the minibuffer as a @dfn{prompt} to remind you to enter a
command name to be run.  @key{RET} exits the minibuffer and runs the
command.  @xref{Minibuffer}, for more information on the minibuffer.

  You can use completion to enter the command name.  For example,
to invoke the command @code{forward-char}, you can type

@example
M-x forward-char @key{RET}
@end example

@noindent
or

@example
M-x forw @key{TAB} c @key{RET}
@end example

@noindent
Note that @code{forward-char} is the same command that you invoke with
the key @kbd{C-f}.  The existence of a key binding does not stop you
from running the command by name.

@cindex obsolete command
  When @kbd{M-x} completes on commands, it ignores the commands that
are declared @dfn{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.)

@vindex read-extended-command-predicate
  In addition, @kbd{M-x} completion can exclude commands that are not
relevant to, and generally cannot work with, the current buffer's
major mode (@pxref{Major Modes}) and minor modes (@pxref{Minor
Modes}).  By default, no commands are excluded, but you can customize
the option @code{read-extended-command-predicate} to exclude those
irrelevant commands from completion results.

@kindex M-S-x
@kindex M-X
  Conversely, Emacs can exclude all commands except those that are
particularly relevant to the current buffer.  The @kbd{M-S-x} (that's
``meta shift x'') command works just like @kbd{M-x}, but instead of
listing all (or most) of the commands Emacs knows about, it will only
list the commands that have been marked as ``belonging'' to the
current major mode, or any enabled minor modes.

  To cancel the @kbd{M-x} and not run a command, type @kbd{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
@kbd{M-x}, specify the numeric argument before @kbd{M-x}.  The
argument value appears in the prompt while the command name is being
read, and finally @kbd{M-x} passes the argument to that command.  For
example, to pass the numeric argument of 42 to the command
@code{forward-char} you can type @kbd{C-u 42 M-x forward-char
@key{RET}}.

@vindex suggest-key-bindings
  When the command you run with @kbd{M-x} has a key binding, Emacs
mentions this in the echo area after running the command.  For
example, if you type @kbd{M-x forward-word}, the message says that you
can run the same command by typing @kbd{M-f}.  You can turn off these
messages by setting the variable @code{suggest-key-bindings} to
@code{nil}.  The value of @code{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.

Additionally, when @code{suggest-key-bindings} is non-@code{nil}, the
completion list of @kbd{M-x} shows equivalent key bindings for all
commands that have them.

@vindex extended-command-suggest-shorter
  Commands that don't have key bindings, can still be invoked after
typing less than their full name at the @samp{M-x} prompt.  Emacs
mentions such shorthands in the echo area if they are significantly
shorter than the full command name, and
@code{extended-command-suggest-shorter} is non-@code{nil}.  The
setting of @code{suggest-key-bindings} affects these hints as well.

  In this manual, when we speak of running a command by name, we often
omit the @key{RET} that terminates the name.  Thus we might say
@kbd{M-x auto-fill-mode} rather than @w{@kbd{M-x auto-fill-mode
@key{RET}}}.  We mention the @key{RET} only for emphasis, such as when
the command is followed by arguments.

@findex execute-extended-command
  @kbd{M-x} works by running the command
@code{execute-extended-command}, which is responsible for reading the
name of another command and invoking it.
