1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), this list of conditions and the following disclaimer in 13.\" the documentation and/or other materials provided with the 14.\" distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 20.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 23.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 25.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 26.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27.\" 28.Dd September 6, 2013 29.Dt SIGWAIT 2 30.Os 31.Sh NAME 32.Nm sigwait 33.Nd select a set of signals 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In signal.h 38.Ft int 39.Fn sigwait "const sigset_t * restrict set" "int * restrict sig" 40.Sh DESCRIPTION 41The 42.Fn sigwait 43system call selects a set of signals, specified by 44.Fa set . 45If none of the selected signals are pending, 46.Fn sigwait 47waits until one or more of the selected signals has been generated. 48Then 49.Fn sigwait 50atomically clears one of the selected signals from the set of pending signals 51(for the process or for the current thread) and sets the location pointed to by 52.Fa sig 53to the signal number that was cleared. 54.Pp 55The signals specified by 56.Fa set 57should be blocked at the time of the call to 58.Fn sigwait . 59.Pp 60If more than one thread is using 61.Fn sigwait 62to wait for the same signal, no more than one of these threads will return from 63.Fn sigwait 64with the signal number. 65If more than a single thread is blocked in 66.Fn sigwait 67for a signal when that signal is generated for the process, it is unspecified 68which of the waiting threads returns from 69.Fn sigwait . 70If the signal is generated for a specific thread, as by 71.Fn pthread_kill , 72only that thread will return. 73.Pp 74Should any of the multiple pending signals in the range 75.Dv SIGRTMIN 76to 77.Dv SIGRTMAX 78be 79selected, it will be the lowest numbered one. 80The selection order between realtime 81and non-realtime signals, or between multiple pending non-realtime signals, 82is unspecified. 83.Sh IMPLEMENTATION NOTES 84The 85.Fn sigwait 86function is implemented as a wrapper around the 87.Fn __sys_sigwait 88system call, which retries the call on 89.Er EINTR 90error. 91.Sh RETURN VALUES 92If successful, 93.Fn sigwait 94returns 0 and sets the location pointed to by 95.Fa sig 96to the cleared signal number. 97Otherwise, an error number is returned. 98.Sh ERRORS 99The 100.Fn sigwait 101system call will fail if: 102.Bl -tag -width Er 103.It Bq Er EINVAL 104The 105.Fa set 106argument 107specifies one or more invalid signal numbers. 108.El 109.Sh SEE ALSO 110.Xr sigaction 2 , 111.Xr sigpending 2 , 112.Xr sigqueue 2 , 113.Xr sigsuspend 2 , 114.Xr sigtimedwait 2 , 115.Xr sigwaitinfo 2 , 116.Xr pause 3 , 117.Xr pthread_sigmask 3 118.Sh STANDARDS 119The 120.Fn sigwait 121function conforms to 122.St -p1003.1-96 . 123