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 January 12, 2009 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. 77If the 78.Fa evp 79argument is 80.Dv NULL , 81the effect is as if the 82.Fa evp 83argument pointed to a 84.Vt sigevent 85structure with the 86.Va sigev_notify 87member having the value 88.Dv SIGEV_SIGNAL , 89the 90.Va sigev_signo 91having a default signal number, and the 92.Va sigev_value 93member having 94the value of the timer ID. 95.Pp 96The implementations supports a 97.Fa clock_id 98of 99.Dv CLOCK_REALTIME 100or 101.Dv CLOCK_MONOTONIC . 102.Pp 103If 104.Fa evp->sigev_notify 105is 106.Dv SIGEV_THREAD 107and 108.Fa sev->sigev_notify_attributes 109is not 110.Dv NULL , 111if the attribute pointed to by 112.Fa sev->sigev_notify_attributes 113has 114a thread stack address specified by a call to 115.Fn pthread_attr_setstack 116or 117.Fn pthread_attr_setstackaddr , 118the results are unspecified if the signal is generated more than once. 119.Sh RETURN VALUES 120If the call succeeds, 121.Fn timer_create 122returns zero and updates the location referenced by 123.Fa timerid 124to a 125.Vt timer_t , 126which can be passed to the per-process timer calls. 127If an error 128occurs, the system call returns a value of \-1 129and the global variable 130.Va errno 131is set to indicate the 132error. 133The value of 134.Fa timerid 135is undefined if an error occurs. 136.Sh ERRORS 137The 138.Fn timer_create 139system call 140will fail if: 141.Bl -tag -width Er 142.It Bq Er EAGAIN 143The calling process has already created all of the timers it is allowed by 144this implementation. 145.It Bq Er EINVAL 146The specified clock ID is not supported. 147.It Bq Er EFAULT 148Any arguments point outside the allocated address space or there is a 149memory protection fault. 150.El 151.Sh SEE ALSO 152.Xr clock_getres 2 , 153.Xr timer_delete 2 , 154.Xr timer_getoverrun 2 , 155.Xr siginfo 3 156.Sh STANDARDS 157The 158.Fn timer_create 159system call conforms to 160.St -p1003.1-2004 . 161.Sh HISTORY 162Support for 163.Tn POSIX 164per-process timer first appeared in 165.Fx 7.0 . 166