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 .\" $FreeBSD$ 29 .\" 30 .Dd July 15, 2016 31 .Dt TIMER_CREATE 2 32 .Os 33 .Sh NAME 34 .Nm timer_create 35 .Nd "create a per-process timer (REALTIME)" 36 .Sh LIBRARY 37 .Lb librt 38 .Sh SYNOPSIS 39 .In time.h 40 .In signal.h 41 .Ft int 42 .Fo timer_create 43 .Fa "clockid_t clockid" "struct sigevent *restrict evp" 44 .Fa "timer_t *restrict timerid" 45 .Fc 46 .Sh DESCRIPTION 47The 48 .Fn timer_create 49system call creates a per-process timer using the specified clock, 50 .Fa clock_id , 51as the timing base. 52The 53 .Fn timer_create 54system call returns, in the location referenced by 55 .Fa timerid , 56a timer ID of type 57 .Vt timer_t 58used to identify the timer in timer requests. 59This timer ID is unique within the calling process until the timer is deleted. 60The particular clock, 61 .Fa clock_id , 62is defined in 63 .In time.h . 64The timer whose ID is returned is in a disarmed state upon return from 65 .Fn timer_create . 66 .Pp 67The 68 .Fa evp 69argument, if 70 .Pf non- Dv NULL , 71points to a 72 .Vt sigevent 73structure. 74This structure, 75allocated by the application, defines the asynchronous notification to occur 76when the timer expires. 77 .Pp 78If 79 .Fa evp->sigev_notify 80is 81 .Dv SIGEV_SIGNO 82or 83 .Dv SIGEV_THREAD_ID , 84the signal specified in 85 .Fa evp->sigev_signo 86will be sent to the calling process 87 .Pq Dv SIGEV_SIGNO 88or to the thread whose LWP ID is 89 .Fa evp->sigev_notify_thread_id 90 .Pq Dv SIGEV_THREAD_ID . 91The information for the queued signal will include: 92 .Bl -column ".Va si_value" 93 .It Sy Member Ta Sy Value 94 .It Va si_code Ta Dv SI_TIMER 95 .It Va si_value Ta 96the value stored in 97 .Fa evp->sigev_value 98 .It Va si_timerid Ta timer ID 99 .It Va si_overrun Ta timer overrun count 100 .It Va si_errno Ta 101If timer overrun is 102 .Brq Dv DELAYTIMER_MAX , 103an error code defined in 104 .In errno.h 105 .El 106 .Pp 107If the 108 .Fa evp 109argument is 110 .Dv NULL , 111the effect is as if the 112 .Fa evp 113argument pointed to a 114 .Vt sigevent 115structure with the 116 .Va sigev_notify 117member having the value 118 .Dv SIGEV_SIGNAL , 119the 120 .Va sigev_signo 121having a default signal number 122 .Pq Dv SIGALRM , 123and the 124 .Va sigev_value 125member having 126the value of the timer ID. 127 .Pp 128This implementation supports a 129 .Fa clock_id 130of 131 .Dv CLOCK_REALTIME 132or 133 .Dv CLOCK_MONOTONIC . 134 .Pp 135If 136 .Fa evp->sigev_notify 137is 138 .Dv SIGEV_THREAD 139and 140 .Fa sev->sigev_notify_attributes 141is not 142 .Dv NULL , 143if the attribute pointed to by 144 .Fa sev->sigev_notify_attributes 145has 146a thread stack address specified by a call to 147 .Fn pthread_attr_setstack 148or 149 .Fn pthread_attr_setstackaddr , 150the results are unspecified if the signal is generated more than once. 151 .Sh RETURN VALUES 152If the call succeeds, 153 .Fn timer_create 154returns zero and updates the location referenced by 155 .Fa timerid 156to a 157 .Vt timer_t , 158which can be passed to the per-process timer calls. 159If an error 160occurs, the system call returns a value of \-1 161and the global variable 162 .Va errno 163is set to indicate the 164error. 165The value of 166 .Fa timerid 167is undefined if an error occurs. 168 .Sh ERRORS 169The 170 .Fn timer_create 171system call 172will fail if: 173 .Bl -tag -width Er 174 .It Bq Er EAGAIN 175The calling process has already created all of the timers it is allowed by 176this implementation. 177 .It Bq Er EINVAL 178The specified clock ID is not supported. 179 .It Bq Er EINVAL 180The specified asynchronous notification method is not supported. 181 .It Bq Er EFAULT 182Any arguments point outside the allocated address space or there is a 183memory protection fault. 184 .El 185 .Sh SEE ALSO 186 .Xr clock_getres 2 , 187 .Xr timer_delete 2 , 188 .Xr timer_getoverrun 2 , 189 .Xr sigevent 3 , 190 .Xr siginfo 3 191 .Sh STANDARDS 192The 193 .Fn timer_create 194system call conforms to 195 .St -p1003.1-2004 . 196 .Sh HISTORY 197Support for 198 .Tn POSIX 199per-process timer first appeared in 200 .Fx 7.0 . 201