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NAME

     sigtimedwait, sigwaitinfo - wait for queued signals (REALTIME)

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <signal.h>

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

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

DESCRIPTION

     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.

RETURN VALUES

     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.

ERRORS

     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
                        signal.

     [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.

SEE ALSO

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

STANDARDS

     The sigtimedwait() and sigwaitinfo() system calls conform to ISO/IEC
     9945-1:1996 (“POSIX.1”).