128 lines
3.7 KiB
Groff
128 lines
3.7 KiB
Groff
.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 24, 2011
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.Dt SIGWAIT 2
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.Os
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.Sh NAME
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.Nm sigwait
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.Nd select a set of signals
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In signal.h
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.Ft int
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.Fn sigwait "const sigset_t * restrict set" "int * restrict sig"
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.Sh DESCRIPTION
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The
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.Fn sigwait
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system call selects a set of signals, specified by
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.Fa set .
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If none of the selected signals are pending,
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.Fn sigwait
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waits until one or more of the selected signals has been generated.
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Then
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.Fn sigwait
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atomically clears one of the selected signals from the set of pending signals
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for the process and sets the location pointed to by
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.Fa sig
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to the signal number that was cleared.
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.Pp
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The signals specified by
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.Fa set
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should be blocked at the time of the call to
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.Fn sigwait .
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.Pp
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If more than one thread is using
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.Fn sigwait
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to wait for the same signal, no more than one of these threads will return from
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.Fn sigwait
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with the signal number.
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If more than a single thread is blocked in
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.Fn sigwait
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for a signal when that signal is generated for the process, it is unspecified
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which of the waiting threads returns from
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.Fn sigwait .
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If the signal is generated for a specific thread, as by
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.Fn pthread_kill ,
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only that thread will return.
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.Pp
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Should any of the multiple pending signals in the range
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.Dv SIGRTMIN
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to
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.Dv SIGRTMAX
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be
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selected, it will be the lowest numbered one.
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The selection order between realtime
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and non-realtime signals, or between multiple pending non-realtime signals,
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is unspecified.
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.Sh IMPLEMENTATION NOTES
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The
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.Fn sigwait
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function is implemented as a wrapper around the
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.Fn __sys_sigwait
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system call, which retries the call on
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.Er EINTR
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error.
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.Sh RETURN VALUES
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If successful,
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.Fn sigwait
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returns 0 and sets the location pointed to by
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.Fa sig
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to the cleared signal number.
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Otherwise, an error number is returned.
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.Sh ERRORS
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The
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.Fn sigwait
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa set
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argument
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specifies one or more invalid signal numbers.
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.It Bq Er EFAULT
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Any arguments point outside the allocated address space or there is a
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memory protection fault.
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.El
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr sigpending 2 ,
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.Xr sigqueue 2 ,
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.Xr sigsuspend 2 ,
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.Xr sigtimedwait 2 ,
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.Xr sigwaitinfo 2 ,
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.Xr pause 3 ,
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.Xr pthread_sigmask 3
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.Sh STANDARDS
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The
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.Fn sigwait
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function conforms to
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.St -p1003.1-96 .
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