I have program that runs for long periods of time and I'd like to interrupt it but not with ctrl-c ctrl-c. I also don't want the system to wait for a keystroke every so often. Instead, if I do press a key, I want it to wrap things up and exit. I found listen and read-char-no-hang but I can't get it to work right. Here's what I tried to do
(let ((f nil))
(loop while (not f) do
(if (listen)
(setf f t)))))
Obviously, this is doing less than a sloth on Xanax as far as finding key=-presses. What am I doing wrong?
CCL has multithreading, I believe. You could try spawning a worker thread in the background and have a control thread doing a blocking read, and then communicating via a special variable. The following works in Lispworks, I don't have CCL available. You'd have to translate the mp:process-run-function to whatever CCL uses to spawn threads:
(defparameter *f* nil)
(defun cmd-loop ()
(setf *f* nil)
(mp:process-run-function "work" () #'do-work) ; Spawn worker
(read-char *terminal-io*) ; Blocking read
(setf *f* t))
(defun do-work ()
(loop while (not *f*)
do
(format t "~a " *f*)
(finish-output)))
(cmd-loop)
The big assumption I'm making here is that CCL multithreading works similarily to LW multithreading, so that both threads can access the shared state variable *f*.