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$FreeBSD: head/lib/libc/sys/sigwait.2 225172 2011-08-25 10:00:38Z kib $
.Dd August 24, 2011 .Dt SIGWAIT 2 .Os .Sh NAME .Nm sigwait .Nd select a set of signals .Sh LIBRARY .Lb libc .Sh SYNOPSIS n signal.h .Ft int .Fn sigwait "const sigset_t * restrict set" "int * restrict sig" .Sh DESCRIPTION The .Fn sigwait system call selects a set of signals, specified by .Fa set . If none of the selected signals are pending, .Fn sigwait waits until one or more of the selected signals has been generated. Then .Fn sigwait atomically clears one of the selected signals from the set of pending signals for the process and sets the location pointed to by .Fa sig to the signal number that was cleared.
p The signals specified by .Fa set should be blocked at the time of the call to .Fn sigwait .
p If more than one thread is using .Fn sigwait to wait for the same signal, no more than one of these threads will return from .Fn sigwait with the signal number. If more than a single thread is blocked in .Fn sigwait for a signal when that signal is generated for the process, it is unspecified which of the waiting threads returns from .Fn sigwait . If the signal is generated for a specific thread, as by .Fn pthread_kill , only that thread will return.
p Should any of the multiple pending signals in the range .Dv SIGRTMIN to .Dv 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. .Sh IMPLEMENTATION NOTES The .Fn sigwait function is implemented as a wrapper around the .Fn __sys_sigwait system call, which retries the call on .Er EINTR error. .Sh RETURN VALUES If successful, .Fn sigwait returns 0 and sets the location pointed to by .Fa sig to the cleared signal number. Otherwise, an error number is returned. .Sh ERRORS The .Fn sigwait system call will fail if: l -tag -width Er t Bq Er EINVAL The .Fa set argument specifies one or more invalid signal numbers. t Bq Er EFAULT Any arguments point outside the allocated address space or there is a memory protection fault. .El .Sh SEE ALSO .Xr sigaction 2 , .Xr sigpending 2 , .Xr sigqueue 2 , .Xr sigsuspend 2 , .Xr sigtimedwait 2 , .Xr sigwaitinfo 2 , .Xr pause 3 , .Xr pthread_sigmask 3 .Sh STANDARDS The .Fn sigwait function conforms to .St -p1003.1-96 .