199 lines
4.9 KiB
Groff
199 lines
4.9 KiB
Groff
.\" Copyright (c) 2005 David Xu <davidxu@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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.Dd July 15, 2016
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.Dt TIMER_CREATE 2
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.Os
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.Sh NAME
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.Nm timer_create
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.Nd "create a per-process timer (REALTIME)"
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.Sh LIBRARY
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.Lb librt
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.Sh SYNOPSIS
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.In time.h
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.In signal.h
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.Ft int
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.Fo timer_create
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.Fa "clockid_t clockid" "struct sigevent *restrict evp"
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.Fa "timer_t *restrict timerid"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn timer_create
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system call creates a per-process timer using the specified clock,
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.Fa clock_id ,
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as the timing base.
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The
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.Fn timer_create
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system call returns, in the location referenced by
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.Fa timerid ,
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a timer ID of type
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.Vt timer_t
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used to identify the timer in timer requests.
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This timer ID is unique within the calling process until the timer is deleted.
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The particular clock,
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.Fa clock_id ,
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is defined in
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.In time.h .
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The timer whose ID is returned is in a disarmed state upon return from
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.Fn timer_create .
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.Pp
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The
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.Fa evp
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argument, if
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.Pf non- Dv NULL ,
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points to a
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.Vt sigevent
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structure.
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This structure,
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allocated by the application, defines the asynchronous notification to occur
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when the timer expires.
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.Pp
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If
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.Fa evp->sigev_notify
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is
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.Dv SIGEV_SIGNO
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or
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.Dv SIGEV_THREAD_ID ,
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the signal specified in
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.Fa evp->sigev_signo
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will be sent to the calling process
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.Pq Dv SIGEV_SIGNO
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or to the thread whose LWP ID is
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.Fa evp->sigev_notify_thread_id
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.Pq Dv SIGEV_THREAD_ID .
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The information for the queued signal will include:
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.Bl -column ".Va si_value"
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.It Sy Member Ta Sy Value
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.It Va si_code Ta Dv SI_TIMER
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.It Va si_value Ta
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the value stored in
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.Fa evp->sigev_value
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.It Va si_timerid Ta timer ID
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.It Va si_overrun Ta timer overrun count
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.It Va si_errno Ta
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If timer overrun is
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.Brq Dv DELAYTIMER_MAX ,
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an error code defined in
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.In errno.h
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.El
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.Pp
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If the
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.Fa evp
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argument is
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.Dv NULL ,
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the effect is as if the
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.Fa evp
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argument pointed to a
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.Vt sigevent
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structure with the
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.Va sigev_notify
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member having the value
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.Dv SIGEV_SIGNAL ,
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the
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.Va sigev_signo
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having a default signal number
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.Pq Dv SIGALRM ,
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and the
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.Va sigev_value
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member having
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the value of the timer ID.
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.Pp
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This implementation supports a
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.Fa clock_id
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of
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.Dv CLOCK_REALTIME
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or
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.Dv CLOCK_MONOTONIC .
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.Pp
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If
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.Fa evp->sigev_notify
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is
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.Dv SIGEV_THREAD
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and
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.Fa sev->sigev_notify_attributes
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is not
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.Dv NULL ,
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if the attribute pointed to by
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.Fa sev->sigev_notify_attributes
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has
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a thread stack address specified by a call to
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.Fn pthread_attr_setstack
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or
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.Fn pthread_attr_setstackaddr ,
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the results are unspecified if the signal is generated more than once.
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.Sh RETURN VALUES
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If the call succeeds,
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.Fn timer_create
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returns zero and updates the location referenced by
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.Fa timerid
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to a
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.Vt timer_t ,
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which can be passed to the per-process timer calls.
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If an error
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occurs, the system call returns a value of \-1
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and the global variable
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.Va errno
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is set to indicate the
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error.
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The value of
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.Fa timerid
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is undefined if an error occurs.
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.Sh ERRORS
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The
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.Fn timer_create
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EAGAIN
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The calling process has already created all of the timers it is allowed by
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this implementation.
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.It Bq Er EINVAL
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The specified clock ID is not supported.
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.It Bq Er EINVAL
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The specified asynchronous notification method is not supported.
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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 clock_getres 2 ,
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.Xr timer_delete 2 ,
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.Xr timer_getoverrun 2 ,
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.Xr sigevent 3 ,
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.Xr siginfo 3
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.Sh STANDARDS
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The
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.Fn timer_create
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system call conforms to
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.St -p1003.1-2004 .
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.Sh HISTORY
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Support for
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.Tn POSIX
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per-process timer first appeared in
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.Fx 7.0 .
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