doc/manual/timers.texinfo

   1 @node Timers
   2 @comment  node-name,  next,  previous,  up
   3 @chapter Timers
   4
   5 SBCL supports a system-wide event scheduler implemented on top of
   6 @code{setitimer} that also works with threads but does not require a
   7 separate scheduler thread.
   8
   9 The following example schedules a timer that writes ``Hello, word'' after
  10 two seconds.
  11
  12 @lisp
  13 (schedule-timer (make-timer (lambda ()
  14                               (write-line "Hello, world")
  15                               (force-output)))
  16                 2)
  17 @end lisp
  18
  19 It should be noted that writing timer functions requires special care,
  20 as the dynamic environment in which they run is unpredictable: dynamic
  21 variable bindings, locks held, etc, all depend on whatever code was
  22 running when the timer fired. The following example should serve as
  23 a cautionary tale:
  24
  25 @lisp
  26 (defvar *foo* nil)
  27
  28 (defun show-foo ()
  29   (format t "~&foo=~S~%" *foo*)
  30   (force-output t))
  31
  32 (defun demo ()
  33   (schedule-timer (make-timer #'show-foo) 0.5)
  34   (schedule-timer (make-timer #'show-foo) 1.5)
  35   (let ((*foo* t))
  36     (sleep 1.0))
  37   (let ((*foo* :surprise!))
  38     (sleep 2.0)))
  39 @end lisp
  40
  41 @section Timer Dictionary
  42
  43 @include struct-sb-ext-timer.texinfo
  44 @include fun-sb-ext-make-timer.texinfo
  45 @include fun-sb-ext-timer-name.texinfo
  46 @include fun-sb-ext-timer-scheduled-p.texinfo
  47 @include fun-sb-ext-schedule-timer.texinfo
  48 @include fun-sb-ext-unschedule-timer.texinfo
  49 @include fun-sb-ext-list-all-timers.texinfo