Returns the number of ticks remaining till the next tick interrupt. Ticks are an arbitrary unit of evaluation. Ticks can vary greatly in the amount of time they represent.
If n is 0, any ticks request is canceled. Otherwise a
ticks-interruptwill be signaled n from the current time.
ticksis supported if SCM is compiled with the
Establishes a response for tick interrupts. Another tick interrupt will not occur unless
ticksis called again. Program execution will resume if the handler returns. This procedure should (abort) or some other action which does not return if it does not want processing to continue.
Returns the number of seconds remaining till the next alarm interrupt. If secs is 0, any alarm request is canceled. Otherwise an
alarm-interruptwill be signaled secs from the current time. ALARM is not supported on all systems.
milli-alarmis similar to
alarm, except that the first argument millisecs, and the return value are measured in milliseconds rather than seconds. If the optional argument interval is supplied then alarm interrupts will be scheduled every interval milliseconds until turned off by a call to
virtual-alarmdecrements process execution time rather than real time, and causes
SIGVTALRMto be signaled.
profile-alarmdecrements both process execution time and system execution time on behalf of the process, and causes
SIGPROFto be signaled.
profile-alarmare supported only on systems providing the
Establishes a response for
SIGINT(control-C interrupt) and
SIGPROFinterrupts. Program execution will resume if the handler returns. This procedure should
(abort)or some other action which does not return if it does not want processing to continue after it returns.
Interrupt handlers are disabled during execution
To unestablish a response for an interrupt set the handler symbol to
#f. For instance,
(set! user-interrupt #f).
Establishes a response for storage allocation error, file opening error, end of program, SIGHUP (hang up interrupt) and arithmetic errors respectively. This procedure should (abort) or some other action which does not return if it does not want the default error message to also be displayed. If no procedure is defined for hang-up then end-of-program (if defined) will be called.
To unestablish a response for an error set the handler symbol to
#f. For instance,
(set! could-not-open #f).