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-interrupt will be signaled n from the current time.
ticks is supported if SCM is compiled with the
Establishes a response for tick interrupts. Another tick interrupt will
not occur unless
ticks is 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
Returns the number of seconds remaining till the next alarm interrupt.
If secs is 0, any alarm request is canceled. Otherwise an
alarm-interrupt will be signaled secs from the current
time. ALARM is not supported on all systems.
milli-alarm is 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
profile-alarm are similar.
virtual-alarm decrements process execution time rather than real
time, and causes
SIGVTALRM to be signaled.
profile-alarm decrements both process execution time and
system execution time on behalf of the process, and causes
SIGPROF to be signaled.
supported only on systems providing the
setitimer system call.
Establishes a response for
SIGINT (control-C interrupt) and
Program execution will resume if the handler returns. This procedure
(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).