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SIGTIMEDWAIT(2)		  FreeBSD System Calls Manual	       SIGTIMEDWAIT(2)

     sigtimedwait, sigwaitinfo -- wait for queued signals (REALTIME)

     Standard C	Library	(libc, -lc)

     #include <signal.h>

     sigtimedwait(const	sigset_t *restrict set,	siginfo_t *restrict info,
	 const struct timespec *restrict timeout);

     sigwaitinfo(const sigset_t	* restrict set,	siginfo_t * restrict info);

     The sigtimedwait()	system call is equivalent to sigwaitinfo() except that
     if	none of	the signals specified by set are pending, sigtimedwait() waits
     for the time interval specified in	the timespec structure referenced by
     timeout.  If the timespec structure pointed to by timeout is zero-valued
     and if none of the	signals	specified by set are pending, then
     sigtimedwait() returns immediately	with an	error.	If timeout is the NULL
     pointer, sigtimedwait() blocks indefinitely.  CLOCK_MONOTONIC clock is
     used to measure the time interval specified by the	timeout	argument.

     The sigwaitinfo() system call selects the pending signal from the set
     specified by set.	Should any of multiple pending signals in the range
     SIGRTMIN to SIGRTMAX be selected, it shall	be the lowest numbered one.
     The selection order between realtime and non-realtime signals, or between
     multiple pending non-realtime signals, is unspecified.  If	no signal in
     set is pending at the time	of the call, the calling thread	is suspended
     until one or more signals in set become pending or	until it is inter-
     rupted by an unblocked, caught signal.

     The sigwaitinfo() system call is equivalent to the	sigwait() system call
     if	the info argument is NULL.  If the info	argument is non-NULL, the
     sigwaitinfo() function is equivalent to sigwait(),	except that the	se-
     lected signal number shall	be stored in the si_signo member, and the
     cause of the signal shall be stored in the	si_code	member.	 Besides this,
     the sigwaitinfo() and sigtimedwait() system calls may return EINTR	if in-
     terrupted by signal, which	is not allowed for the sigwait() function.

     If	any value is queued to the selected signal, the	first such queued
     value is dequeued and, if the info	argument is non-NULL, the value	is
     stored in the si_value member of info.  The system	resource used to queue
     the signal	is released and	returned to the	system for other use.  If no
     value is queued, the content of the si_value member is zero-valued.  If
     no	further	signals	are queued for the selected signal, the	pending	indi-
     cation for	that signal is reset.

     Upon successful completion	(that is, one of the signals specified by set
     is	pending	or is generated) sigwaitinfo() and sigtimedwait() return the
     selected signal number.  Otherwise, the functions return a	value of -1
     and set the global	variable errno to indicate the error.

     The sigtimedwait()	system call will fail if:

     [EAGAIN]		No signal specified by set was generated within	the
			specified timeout period.

     The sigtimedwait()	and sigwaitinfo() system calls fail if:

     [EINTR]		The wait was interrupted by an unblocked, caught sig-

     The sigtimedwait()	system call may	also fail if:

     [EINVAL]		The timeout argument specified a tv_nsec value less
			than zero or greater than or equal to 1000 million.
			Kernel only checks for this error if no	signal is
			pending	in set and it is necessary to wait.

     sigaction(2), sigpending(2), sigqueue(2), sigsuspend(2), sigwait(2),
     pause(3), pthread_sigmask(3), siginfo(3)

     The sigtimedwait()	and sigwaitinfo() system calls conform to ISO/IEC
     9945-1:1996 ("POSIX.1").  POSIX leaves the	behavior of sigtimedwait()
     with a NULL timeout pointer unspecified.

FreeBSD	13.0			April 21, 2022			  FreeBSD 13.0


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