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GNU Emacs Lisp Reference Manual

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38.4 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 section `The Minibuffer' in The GNU Emacs Manual). Error messages appear in the echo area; see 10.5.3 Errors.

You can write output in the echo area by using the Lisp printing functions with t as the stream (see section 19.5 Output Functions), or as follows:

Function: message string &rest arguments
This function displays a message in the echo area. The argument string is similar to a C language printf control string. See format in 4.6 Conversion of Characters and Strings, 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, or strings among the arguments, have face text properties, these affect the way the message is displayed.

If string is nil, message clears the echo area; if the echo area has been expanded automatically, this brings it back to its normal size. If the minibuffer is active, this brings the minibuffer contents back onto the screen immediately.

Normally, displaying a long message resizes the echo area to display the entire message. But if the variable message-truncate-lines is non-nil, the echo area does not resize, and the message is truncated to fit it, as in Emacs 20 and before.

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

---------- Echo Area ----------
Minibuffer depth is 0.
---------- Echo Area ----------

To automatically display a message in the echo area or in a pop-buffer, depending on its size, use display-message-or-buffer.

Macro: with-temp-message message &rest body
This construct displays a message in the echo area temporarily, during the execution of body. It displays message, executes body, then returns the value of the last body form while restoring the previous echo area contents.

Function: message-or-box string &rest arguments
This function displays a message like message, but may display it in a dialog box instead of the echo area. If this function is called in a command that was invoked using the mouse--more precisely, if last-nonmenu-event (see section 21.4 Information from the Command Loop) is either nil or a list--then it uses a dialog box or pop-up menu to display the message. Otherwise, it uses the echo area. (This is the same criterion that y-or-n-p uses to make a similar decision; see 20.6 Yes-or-No Queries.)

You can force use of the mouse or of the echo area by binding last-nonmenu-event to a suitable value around the call.

Function: message-box string &rest arguments
This function displays a message like message, but uses a dialog box (or a pop-up menu) whenever that is possible. If it is impossible to use a dialog box or pop-up menu, because the terminal does not support them, then message-box uses the echo area, like message.

Function: display-message-or-buffer message &optional buffer-name not-this-window frame
This function displays the message message, which may be either a string or a buffer. If it is shorter than the maximum height of the echo area, as defined by max-mini-window-height, it is displayed in the echo area, using message. Otherwise, display-buffer is used to show it in a pop-up buffer.

Returns either the string shown in the echo area, or when a pop-up buffer is used, the window used to display it.

If message is a string, then the optional argument buffer-name is the name of the buffer used to display it when a pop-up buffer is used, defaulting to `*Message*'. In the case where message is a string and displayed in the echo area, it is not specified whether the contents are inserted into the buffer anyway.

The optional arguments not-this-window and frame are as for display-buffer, and only used if a buffer is displayed.

Function: current-message
This function returns the message currently being displayed in the echo area, or nil if there is none.

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.

Variable: echo-area-clear-hook
This normal hook is run whenever the echo area is cleared--either by (message nil) or for any other reason.

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 or floating point number, 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. (Once echoing begins in a key sequence, all subsequent characters in the same key sequence are echoed immediately.)

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


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