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
(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
y-or-n-p use the minibuffer.
This function asks the user a question, expecting input in the minibuffer.
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-] and C-g to quit,
because the question uses the 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 minibuffer, 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 actually uses the minibuffer, but does not allow editing of the answer. The cursor moves to the minibuffer while the question is being asked.
The answers and their meanings, even ‘y’ and ‘n’, are not
hardwired, and are specified by the keymap
(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.
If you bind
help-form (see Help Functions) to
nil value while calling
y-or-n-p, then pressing
help-char causes it to evaluate
help-form and display
help-char is automatically added to prompt.
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 minibuffer,
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 ----------