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sigtimedwait, sigwaitinfo - wait for queued signals (REALTIME)
Standard C Library (libc, -lc)
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, the behavior is unspecified. 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
interrupted 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
selected signal number shall be stored in the si_signo member, and the
cause of the signal shall be stored in the si_code member. 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 indication 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
[EFAULT] Any arguments point outside the allocated address
space or there is a memory protection fault.
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