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SIGWAIT(2)                FreeBSD System Calls Manual               SIGWAIT(2)

NAME
     sigwait - select a set of signals

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <signal.h>

     int
     sigwait(const sigset_t * restrict set, int * restrict sig);

DESCRIPTION
     The sigwait() system call selects a set of signals, specified by set.  If
     none of the selected signals are pending, sigwait() waits until one or
     more of the selected signals has been generated.  Then sigwait()
     atomically clears one of the selected signals from the set of pending
     signals (for the process or for the current thread) and sets the location
     pointed to by sig to the signal number that was cleared.

     The signals specified by set should be blocked at the time of the call to
     sigwait().

     If more than one thread is using sigwait() to wait for the same signal,
     no more than one of these threads will return from sigwait() with the
     signal number.  If more than a single thread is blocked in sigwait() for
     a signal when that signal is generated for the process, it is unspecified
     which of the waiting threads returns from sigwait().  If the signal is
     generated for a specific thread, as by pthread_kill(), only that thread
     will return.

     Should any of the multiple pending signals in the range SIGRTMIN to
     SIGRTMAX be selected, it will be the lowest numbered one.  The selection
     order between realtime and non-realtime signals, or between multiple
     pending non-realtime signals, is unspecified.

IMPLEMENTATION NOTES
     The sigwait() function is implemented as a wrapper around the
     __sys_sigwait() system call, which retries the call on EINTR error.

RETURN VALUES
     If successful, sigwait() returns 0 and sets the location pointed to by
     sig to the cleared signal number.  Otherwise, an error number is
     returned.

ERRORS
     The sigwait() system call will fail if:

     [EINVAL]           The set argument specifies one or more invalid signal
                        numbers.

SEE ALSO
     sigaction(2), sigpending(2), sigqueue(2), sigsuspend(2), sigtimedwait(2),
     sigwaitinfo(2), pause(3), pthread_sigmask(3)

STANDARDS
     The sigwait() function conforms to ISO/IEC 9945-1:1996 (``POSIX.1'').

FreeBSD 11.1-RELEASE-p4        September 6, 2013       FreeBSD 11.1-RELEASE-p4
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