1.\" Copyright (c) 2005 David Xu <[email protected]> 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 September 11, 2000 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.Ft int 41.Fo timer_create 42.Fa "clockid_t clockid" "struct sigevent *restrict evp" 43.Fa "timer_t *restrict timerid" 44.Fc 45.Sh DESCRIPTION 46The 47.Fn timer_create 48system call creates a per-process timer using the specified clock, 49.Fa clock_id , 50as the timing base. 51The 52.Fn timer_create 53system call returns, in the location referenced by 54.Fa timerid , 55a timer ID of type 56.Vt timer_t 57used to identify the timer in timer requests. 58This timer ID is unique within the calling process until the timer is deleted. 59The particular clock, 60.Fa clock_id , 61is defined in 62.In time.h . 63The timer whose ID is returned is in a disarmed state upon return from 64.Fn timer_create . 65.Pp 66The 67.Fa evp 68argument, if 69.Pf non- Dv NULL , 70points to a 71.Vt sigevent 72structure. 73This structure, 74allocated by the application, defines the asynchronous notification to occur 75when the timer expires. 76If the 77.Fa evp 78argument is 79.Dv NULL , 80the effect is as if the 81.Fa evp 82argument pointed to a 83.Vt sigevent 84structure with the 85.Va sigev_notify 86member having the value 87.Dv SIGEV_SIGNAL , 88the 89.Va sigev_signo 90having a default signal number, and the 91.Va sigev_value 92member having 93the value of the timer ID. 94.Pp 95The implementations supports a 96.Fa clock_id 97of 98.Dv CLOCK_REALTIME 99or 100.Dv CLOCK_MONOTONIC . 101.Pp 102If 103.Fa evp->sigev_sigev_notify 104is 105.Dv SIGEV_THREAD 106and 107.Fa sev->sigev_notify_attributes 108is not 109.Dv NULL , 110if the attribute pointed to by 111.Fa sev->sigev_notify_attributes 112has 113a thread stack address specified by a call to 114.Fn pthread_attr_setstack 115or 116.Fn pthread_attr_setstackaddr , 117the results are unspecified if the signal is generated more than once. 118.Sh RETURN VALUES 119If the call succeeds, 120.Fn timer_create 121returns zero and updates the location referenced by 122.Fa timerid 123to a 124.Vt timer_t , 125which can be passed to the per-process timer calls. 126If an error 127occurs, the system call returns a value of \-1 128and the global variable 129.Va errno 130is set to indicate the 131error. 132The value of 133.Fa timerid 134is undefined if an error occurs. 135.Sh ERRORS 136The 137.Fn timer_create 138system call 139will fail if: 140.Bl -tag -width Er 141.It Bq Er EAGAIN 142The calling process has already created all of the timers it is allowed by 143this implementation. 144.It Bq Er EINVAL 145The specified clock ID is not supported. 146.It Bq Er EFAULT 147Any arguments point outside the allocated address space or there is a 148memory protection fault. 149.El 150.Sh SEE ALSO 151.Xr clock_getres 2 , 152.Xr timer_delete 2 , 153.Xr timer_getoverun 2 , 154.Xr siginfo 3 155.Sh STANDARDS 156The 157.Fn timer_create 158system call conforms to 159.St -p1003.1-2004 160.Sh HISTORY 161Support for 162.Tn POSIX 163per-process timer first appeared in 164.Fx 7.0 . 165