— Function: commandp object &optional for-call-interactively

This function returns t if object is a command. Otherwise, it returns nil.

Commands include strings and vectors (which are treated as keyboard macros), lambda expressions that contain a top-level interactive form (see Using Interactive), byte-code function objects made from such lambda expressions, autoload objects that are declared as interactive (non-nil fourth argument to autoload), and some primitive functions. Also, a symbol is considered a command if it has a non-nil interactive-form property, or if its function definition satisfies commandp.

If for-call-interactively is non-nil, then commandp returns t only for objects that call-interactively could call—thus, not for keyboard macros.

See documentation in Accessing Documentation, for a realistic example of using commandp.

— Function: call-interactively command &optional record-flag keys

This function calls the interactively callable function command, providing arguments according to its interactive calling specifications. It returns whatever command returns.

If, for instance, you have a function with the following signature:

          (defun foo (begin end)
            (interactive "r")
            ...)

then saying

          (call-interactively 'foo)

will call foo with the region (point and mark) as the arguments.

An error is signaled if command is not a function or if it cannot be called interactively (i.e., is not a command). Note that keyboard macros (strings and vectors) are not accepted, even though they are considered commands, because they are not functions. If command is a symbol, then call-interactively uses its function definition.

If record-flag is non-nil, then this command and its arguments are unconditionally added to the list command-history. Otherwise, the command is added only if it uses the minibuffer to read an argument. See Command History.

The argument keys, if given, should be a vector which specifies the sequence of events to supply if the command inquires which events were used to invoke it. If keys is omitted or nil, the default is the return value of this-command-keys-vector. See Definition of this-command-keys-vector.

— Function: funcall-interactively function &rest arguments

This function works like funcall (see Calling Functions), but it makes the call look like an interactive invocation: a call to called-interactively-p inside function will return t. If function is not a command, it is called without signaling an error.

— Function: command-execute command &optional record-flag keys special

This function executes command. The argument command must satisfy the commandp predicate; i.e., it must be an interactively callable function or a keyboard macro.

A string or vector as command is executed with execute-kbd-macro. A function is passed to call-interactively (see above), along with the record-flag and keys arguments.

If command is a symbol, its function definition is used in its place. A symbol with an autoload definition counts as a command if it was declared to stand for an interactively callable function. Such a definition is handled by loading the specified library and then rechecking the definition of the symbol.

The argument special, if given, means to ignore the prefix argument and not clear it. This is used for executing special events (see Special Events).

— Command: execute-extended-command prefix-argument

This function reads a command name from the minibuffer using completing-read (see Completion). Then it uses command-execute to call the specified command. Whatever that command returns becomes the value of execute-extended-command.

If the command asks for a prefix argument, it receives the value prefix-argument. If execute-extended-command is called interactively, the current raw prefix argument is used for prefix-argument, and thus passed on to whatever command is run.

execute-extended-command is the normal definition of M-x, so it uses the string ‘M-x ’ as a prompt. (It would be better to take the prompt from the events used to invoke execute-extended-command, but that is painful to implement.) A description of the value of the prefix argument, if any, also becomes part of the prompt.

          (execute-extended-command 3)
          ---------- Buffer: Minibuffer ----------
          3 M-x forward-word <RET>
          ---------- Buffer: Minibuffer ----------
               ⇒ t