GNU Emacs Lisp Reference Manual

35.4: The Echo Area

The echo area is used for displaying messages made with the message primitive, and for echoing keystrokes. It is not the same as the minibuffer, despite the fact that the minibuffer appears (when active) in the same place on the screen as the echo area. The GNU Emacs Manual specifies the rules for resolving conflicts between the echo area and the minibuffer for use of that screen space (see Minibuffer). Error messages appear in the echo area; see Errors.

You can write output in the echo area by using the Lisp printing functions with t as the stream (see Output Functions), or as follows:

Function: message string &rest arguments

This function displays a one-line message in the echo area. The argument string is similar to a C language printf control string. See format in String Conversion, for the details on the conversion specifications. message returns the constructed string.

In batch mode, message prints the message text on the standard error stream, followed by a newline.

If string is nil, message clears the echo area. If the minibuffer is active, this brings the minibuffer contents back onto the screen immediately.

(message "Minibuffer depth is %d."
         (minibuffer-depth))
 -| Minibuffer depth is 0.
=> "Minibuffer depth is 0."
---------- Echo Area ----------
Minibuffer depth is 0.
---------- Echo Area ----------

Almost all the messages displayed in the echo area are also recorded in the *Messages* buffer.

User Option: message-log-max

This variable specifies how many lines to keep in the *Messages* buffer. The value t means there is no limit on how many lines to keep. The value nil disables message logging entirely. Here's how to display a message and prevent it from being logged:

(let (message-log-max)
  (message ...))

Variable: echo-keystrokes

This variable determines how much time should elapse before command characters echo. Its value must be an integer, which specifies the number of seconds to wait before echoing. If the user types a prefix key (such as C-x) and then delays this many seconds before continuing, the prefix key is echoed in the echo area. Any subsequent characters in the same command will be echoed as well.

If the value is zero, then command input is not echoed.

Variable: cursor-in-echo-area

This variable controls where the cursor appears when a message is displayed in the echo area. If it is non-nil, then the cursor appears at the end of the message. Otherwise, the cursor appears at point---not in the echo area at all.

The value is normally nil; Lisp programs bind it to t for brief periods of time.