264 lines
7.2 KiB
Groff
264 lines
7.2 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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.\" $FreeBSD$
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.\"
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.Dd September 11, 2000
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.Dt TIMER_SETTIME 2
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.Os
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.Sh NAME
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.Nm timer_getoverrun ,
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.Nm timer_gettime ,
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.Nm timer_settime
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.Nd "per-process timers (REALTIME)"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In time.h
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.Ft int
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.Fn timer_getoverrun "timer_t timerid"
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.Ft int
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.Fn timer_gettime "timer_t timerid" "struct itimerspec *value"
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.Ft int
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.Fo timer_settime
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.Fa "timer_t timerid" "int flags" "const struct itimerspec *restrict value"
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.Fa "struct itimerspec *restrict ovalue"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn timer_gettime
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system call stores the amount of time until the specified timer,
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.Fa timerid ,
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expires and the reload value of the timer into the space pointed to by the
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.Fa value
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argument.
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The
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.Va it_value
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member of this structure contains the amount of time
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before the timer expires, or zero if the timer is disarmed.
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This value is
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returned as the interval until timer expiration, even if the timer was armed
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with absolute time.
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The
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.Va it_interval
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member of
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.Fa value
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contains the reload
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value last set by
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.Fn timer_settime .
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.Pp
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The
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.Fn timer_settime
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system call sets the time until the next expiration of the timer specified
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by
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.Fa timerid
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from the
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.Va it_value
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member of the
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.Fa value
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argument and arms the timer if the
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.Va it_value
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member of
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.Fa value
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is non-zero.
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If the specified timer was already
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armed when
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.Fn timer_settime
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is called, this call resets the time until next expiration to the value
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specified.
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If the
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.Va it_value
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member of
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.Fa value
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is zero, the timer is disarmed.
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If the timer is disarmed, then pending signal is removed.
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.Pp
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If the flag
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.Dv TIMER_ABSTIME
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is not set in the argument
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.Fa flags ,
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.Fn timer_settime
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behaves as if the time until next expiration is set to
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be equal to the interval specified by the
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.Va it_value
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member of
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.Fa value .
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That is,
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the timer expires in
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.Va it_value
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nanoseconds from when the call is made.
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If the flag
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.Dv TIMER_ABSTIME
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is set in the argument
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.Fa flags ,
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.Fn timer_settime
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behaves as if the time until next expiration is set to be equal to the
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difference between the absolute time specified by the it_value member of
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value and the current value of the clock associated with
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.Fa timerid .
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That is, the timer expires when the clock reaches the value specified by the
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.Va it_value
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member of
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.Fa value .
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If the specified time has already passed, the
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system call succeeds and the expiration notification is made.
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.Pp
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The reload value of the timer is set to the value specified by the
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.Va it_interval
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member of
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.Fa value .
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When a timer is armed with a non-zero
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.Va it_interval ,
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a periodic
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(or repetitive) timer is specified.
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.Pp
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Time values that are between two consecutive non-negative integer multiples of
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the resolution of the specified timer are rounded up to the larger multiple of
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the resolution.
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Quantization error will not cause the timer to expire earlier
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than the rounded time value.
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.Pp
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If the argument
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.Fa ovalue
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is not
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.Dv NULL ,
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the
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.Fn timer_settime
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system call stores, in the location referenced by
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.Fa ovalue ,
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a value representing
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the previous amount of time before the timer would have expired, or zero if the
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timer was disarmed, together with the previous timer reload value.
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Timers do not
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expire before their scheduled time.
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.Pp
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Only a single signal is queued to the process for a given timer at any point in
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time.
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When a timer for which a signal is still pending expires, no signal is
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queued, and a timer overrun will occur.
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When a timer expiration signal is
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accepted by a process, the
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.Fn timer_getoverrun
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system call returns the timer expiration overrun count for the specified timer.
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The overrun count returned contains the number of extra timer expirations that
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occurred between the time the signal was generated (queued) and when it was
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accepted, up to but not including an maximum of
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.Brq Dv DELAYTIMER_MAX .
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If the number of
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such extra expirations is greater than or equal to
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.Brq Dv DELAYTIMER_MAX ,
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then the overrun count is set to
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.Brq Dv DELAYTIMER_MAX .
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The value returned by
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.Fn timer_getoverrun
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applies to the most recent expiration signal acceptance for the timer.
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If no
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expiration signal has been delivered for the timer, the return value of
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.Fn timer_getoverrun
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is unspecified.
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.Sh RETURN VALUES
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If the
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.Fn timer_getoverrun
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system call succeeds, it returns the timer expiration overrun count as explained
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above.
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Otherwise the value \-1 is returned, and the global variable
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.Va errno
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is set to indicate the error.
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.Pp
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.Rv -std timer_gettime timer_settime
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.Sh ERRORS
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The
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.Fn timer_settime
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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 EINVAL
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A
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.Fa value
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structure specified a nanosecond value less than zero or greater than
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or equal to 1000 million, and the
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.Va it_value
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member of that structure did not
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specify zero seconds and nanoseconds.
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.El
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.Pp
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These system calls may 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 timerid
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argument does not correspond to an ID returned by
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.Fn timer_create
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but not yet deleted by
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.Fn timer_delete .
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.El
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.Pp
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The
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.Fn timer_settime
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system call may 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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.Va it_interval
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member of
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.Fa value
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is not zero and the timer was created with
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notification by creation of a new thread
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.Va ( sigev_sigev_notify
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was
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.Dv SIGEV_THREAD )
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and a fixed stack address has been set in the thread attribute pointed to by
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.Va sigev_notify_attributes .
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.El
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.Pp
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The
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.Fn timer_gettime
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and
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.Fn timer_settime
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system calls
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may fail if:
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.Bl -tag -width Er
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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_create 2 ,
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.Xr siginfo 3
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.Sh STANDARDS
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The
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.Fn timer_getoverrun ,
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.Fn timer_gettime ,
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and
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.Fn timer_settime
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system calls conform to
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.St -p1003.1-2004
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.Sh HISTORY
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Support for POSIX per-process timer first appeared in
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.Fx 7.0 .
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