Procedures to raise, handle and wait for signals.
Sends a signal to the specified process or group of processes.
pid specifies the processes to which the signal is sent:
sig should be specified using a variable corresponding to the Unix symbolic name, e.g.,
Sends a specified signal sig to the current process, where sig is as described for the kill procedure.
Install or report the signal hander for a specified signal.
signum is the signal number, which can be specified using the value
of variables such as
If action is omitted,
sigaction returns a pair: the
CAR is the current
signal hander, which will be either an integer with the value
(default action) or
SIG_IGN (ignore), or the Scheme procedure which
handles the signal, or
#f if a non-Scheme procedure handles the
signal. The CDR contains the current
sigaction flags for the handler.
If action is provided, it is installed as the new handler for
action can be a Scheme procedure taking one argument, or the value of
SIG_DFL (default action) or
SIG_IGN (ignore), or
whatever signal handler was installed before
sigaction was first used.
Flags can optionally be specified for the new handler (
always used if the system provides it, so need not be specified.) The
return value is a pair with information about the old handler as
This interface does not provide access to the "signal blocking" facility. Maybe this is not needed, since the thread support may provide solutions to the problem of consistent access to data structures.
sigactionwas made. The return value is unspecified.
SIGALRMsignal after the specified number of seconds (an integer). It's advisable to install a signal handler for
SIGALRMbeforehand, since the default action is to terminate the process.
The return value indicates the time remaining for the previous alarm, if any. The new value replaces the previous alarm. If there was no previous alarm, the return value is zero.
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