This section describes functions used to ask the user a yes-or-no
question. The function
y-or-n-p can be answered with a single
character; it is useful for questions where an inadvertent wrong answer
will not have serious consequences.
yes-or-no-p is suitable for
more momentous questions, since it requires three or four characters to
If either of these functions is called in a command that was invoked
using the mouse—more precisely, if last-nonmenu-event
(see Command Loop Info) is either
nil or a list—then it
uses a dialog box or pop-up menu to ask the question. Otherwise, it
uses keyboard input. You can force use either of the mouse or of keyboard
input by binding last-nonmenu-event to a suitable value around
yes-or-no-p uses the minibuffer and
y-or-n-p does not; but it seems best to describe them together.
This function asks the user a question, expecting input in the echo
area. It returns t if the user types y,
nil if the
user types n. This function also accepts SPC to mean yes
and DEL to mean no. It accepts C-] to quit, like
C-g, because the question might look like a minibuffer and for
that reason the user might try to use C-] to get out. The answer
is a single character, with no RET needed to terminate it. Upper
and lower case are equivalent.
“Asking the question” means printing prompt in the echo area, followed by the string ‘(y or n) ’. If the input is not one of the expected answers (y, n, SPC, DEL, or something that quits), the function responds ‘Please answer y or n.’, and repeats the request.
This function does not actually use the minibuffer, since it does not allow editing of the answer. It actually uses the echo area (see The Echo Area), which uses the same screen space as the minibuffer. The cursor moves to the echo area while the question is being asked.
The answers and their meanings, even ‘y’ and ‘n’, are not
hardwired, and are specified by the keymap query-replace-map
(see Search and Replace). In particular, if the user enters the
scroll-other-window-down (respectively bound to C-l,
C-v, M-v, C-M-v and C-M-S-v in
query-replace-map), this function performs the specified window
recentering or scrolling operation, and poses the question again.
We show successive lines of echo area messages, but only one actually appears on the screen at a time.
y-or-n-p-with-timeoutprompt seconds default
y-or-n-p, except that if the user fails to answer within
seconds seconds, this function stops waiting and returns
default. It works by setting up a timer; see Timers.
The argument seconds should be a number.
This function asks the user a question, expecting input in the
minibuffer. It returns t if the user enters ‘yes’,
nil if the user types ‘no’. The user must type RET to
finalize the response. Upper and lower case are equivalent.
yes-or-no-p starts by displaying prompt in the echo area,
followed by ‘(yes or no) ’. The user must type one of the
expected responses; otherwise, the function responds ‘Please answer
yes or no.’, waits about two seconds and repeats the request.
yes-or-no-p requires more work from the user than
y-or-n-p and is appropriate for more crucial decisions.
Here is an example:
(yes-or-no-p "Do you really want to remove everything? ") ;; After evaluation of the preceding expression, ;; the following prompt appears, ;; with an empty minibuffer:
---------- Buffer: minibuffer ---------- Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ----------
If the user first types y RET, which is invalid because this function demands the entire word ‘yes’, it responds by displaying these prompts, with a brief pause between them:
---------- Buffer: minibuffer ---------- Please answer yes or no. Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ----------