1.\" Copyright (c) 2005 David Xu <davidxu@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 July 15, 2016 29.Dt TIMER_CREATE 2 30.Os 31.Sh NAME 32.Nm timer_create 33.Nd "create a per-process timer (REALTIME)" 34.Sh LIBRARY 35.Lb librt 36.Sh SYNOPSIS 37.In time.h 38.In signal.h 39.Ft int 40.Fo timer_create 41.Fa "clockid_t clockid" "struct sigevent *restrict evp" 42.Fa "timer_t *restrict timerid" 43.Fc 44.Sh DESCRIPTION 45The 46.Fn timer_create 47system call creates a per-process timer using the specified clock, 48.Fa clock_id , 49as the timing base. 50The 51.Fn timer_create 52system call returns, in the location referenced by 53.Fa timerid , 54a timer ID of type 55.Vt timer_t 56used to identify the timer in timer requests. 57This timer ID is unique within the calling process until the timer is deleted. 58The particular clock, 59.Fa clock_id , 60is defined in 61.In time.h . 62The timer whose ID is returned is in a disarmed state upon return from 63.Fn timer_create . 64.Pp 65The 66.Fa evp 67argument, if 68.Pf non- Dv NULL , 69points to a 70.Vt sigevent 71structure. 72This structure, 73allocated by the application, defines the asynchronous notification to occur 74when the timer expires. 75.Pp 76If 77.Fa evp->sigev_notify 78is 79.Dv SIGEV_SIGNO 80or 81.Dv SIGEV_THREAD_ID , 82the signal specified in 83.Fa evp->sigev_signo 84will be sent to the calling process 85.Pq Dv SIGEV_SIGNO 86or to the thread whose LWP ID is 87.Fa evp->sigev_notify_thread_id 88.Pq Dv SIGEV_THREAD_ID . 89The information for the queued signal will include: 90.Bl -column ".Va si_value" 91.It Sy Member Ta Sy Value 92.It Va si_code Ta Dv SI_TIMER 93.It Va si_value Ta 94the value stored in 95.Fa evp->sigev_value 96.It Va si_timerid Ta timer ID 97.It Va si_overrun Ta timer overrun count 98.It Va si_errno Ta 99If timer overrun is 100.Brq Dv DELAYTIMER_MAX , 101an error code defined in 102.In errno.h 103.El 104.Pp 105If the 106.Fa evp 107argument is 108.Dv NULL , 109the effect is as if the 110.Fa evp 111argument pointed to a 112.Vt sigevent 113structure with the 114.Va sigev_notify 115member having the value 116.Dv SIGEV_SIGNAL , 117the 118.Va sigev_signo 119having a default signal number 120.Pq Dv SIGALRM , 121and the 122.Va sigev_value 123member having 124the value of the timer ID. 125.Pp 126This implementation supports a 127.Fa clock_id 128of 129.Dv CLOCK_REALTIME 130or 131.Dv CLOCK_MONOTONIC . 132.Pp 133If 134.Fa evp->sigev_notify 135is 136.Dv SIGEV_THREAD 137and 138.Fa sev->sigev_notify_attributes 139is not 140.Dv NULL , 141if the attribute pointed to by 142.Fa sev->sigev_notify_attributes 143has 144a thread stack address specified by a call to 145.Fn pthread_attr_setstack 146or 147.Fn pthread_attr_setstackaddr , 148the results are unspecified if the signal is generated more than once. 149.Sh RETURN VALUES 150If the call succeeds, 151.Fn timer_create 152returns zero and updates the location referenced by 153.Fa timerid 154to a 155.Vt timer_t , 156which can be passed to the per-process timer calls. 157If an error 158occurs, the system call returns a value of \-1 159and the global variable 160.Va errno 161is set to indicate the 162error. 163The value of 164.Fa timerid 165is undefined if an error occurs. 166.Sh ERRORS 167The 168.Fn timer_create 169system call 170will fail if: 171.Bl -tag -width Er 172.It Bq Er EAGAIN 173The calling process has already created all of the timers it is allowed by 174this implementation. 175.It Bq Er EINVAL 176The specified clock ID is not supported. 177.It Bq Er EINVAL 178The specified asynchronous notification method is not supported. 179.It Bq Er EFAULT 180Any arguments point outside the allocated address space or there is a 181memory protection fault. 182.El 183.Sh SEE ALSO 184.Xr clock_getres 2 , 185.Xr timer_delete 2 , 186.Xr timer_getoverrun 2 , 187.Xr sigevent 3 , 188.Xr siginfo 3 189.Sh STANDARDS 190The 191.Fn timer_create 192system call conforms to 193.St -p1003.1-2004 . 194.Sh HISTORY 195Support for 196.Tn POSIX 197per-process timer first appeared in 198.Fx 7.0 . 199