1.\" 2.\" Redistribution and use in source and binary forms, with or without 3.\" modification, are permitted provided that the following conditions 4.\" are met: 5.\" 1. Redistributions of source code must retain the above copyright 6.\" notice(s), this list of conditions and the following disclaimer as 7.\" the first lines of this file unmodified other than the possible 8.\" addition of one or more copyright notices. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice(s), this list of conditions and the following disclaimer in 11.\" the documentation and/or other materials provided with the 12.\" distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 15.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 17.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 18.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 19.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 20.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 21.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 22.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 23.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 24.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd Sep 11, 2000 29.Dt TIMER_SETTIME 2 30.Os 31.Sh NAME 32.Nm timer_getoverrun 33.Nm timer_gettime 34.Nm timer_settime 35.Nd per-process timers (REALTIME) 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In time.h 40.Ft int 41.Fn timer_getoverrun "timer_t timerid" 42.Ft int 43.Fn timer_gettime "timer_t timerid" "struct itimerspec *value" 44.Ft int 45.Fn timer_settime "timer_t timerid" "int flags" "const struct itimerspec *restrict value" "struct itimerspec *restrict ovalue" 46.Sh DESCRIPTION 47The 48.Fn timer_gettime 49function stores the amount of time until the specified timer, 50.Fa timerid , 51expires and the reload value of the timer into the space pointed to by the 52.Fa value 53argument. The it_value member of this structure contains the amount of time 54before the timer expires, or zero if the timer is disarmed. This value is 55returned as the interval until timer expiration, even if the timer was armed 56with absolute time. The it_interval member of value contains the reload 57value last set by 58.Fn timer_settime . 59.Pp 60The 61.Fn timer_settime 62function sets the time until the next expiration of the timer specified 63by 64.Fa timerid 65from the it_value member of the value argument and arm the timer if the 66it_value member of value is non-zero. If the specified timer was already 67armed when 68.Fn timer_settime 69is called, this call resets the time until next expiration to the value 70specified. If the it_value member of value is zero, the timer is disarmed. 71If the timer is disarmed, then pending signal is removed. 72.Pp 73If the flag TIMER_ABSTIME is not set in the argument 74.Fa flags , 75.Fn timer_settime 76behaves as if the time until next expiration is set to 77be equal to the interval specified by the it_value member of value. That is, 78the timer expires in it_value nanoseconds from when the call is made. If the 79flag TIMER_ABSTIME is set in the argument flags, 80.Fn timer_settime 81behaves as if the time until next expiration is set to be equal to the 82difference between the absolute time specified by the it_value member of 83value and the current value of the clock associated with 84.Fa timerid . 85That is, the timer expires when the clock reaches the value specified by the 86it_value member of value. If the specified time has already passed, the 87function succeeds and the expiration notification is made. 88.Pp 89The reload value of the timer is set to the value specified by the it_interval 90member of value. When a timer is armed with a non-zero it_interval, a periodic 91(or repetitive) timer is specified. 92.Pp 93Time values that are between two consecutive non-negative integer multiples of 94the resolution of the specified timer is rounded up to the larger multiple of 95the resolution. Quantization error will not cause the timer to expire earlier 96than the rounded time value. 97.Pp 98If the argument ovalue is not NULL, the 99.Fn timer_settime 100function stores, in the location referenced by ovalue, a value representing 101the previous amount of time before the timer would have expired, or zero if the 102timer was disarmed, together with the previous timer reload value. Timers is not 103expire before their scheduled time. 104.Pp 105Only a single signal is queued to the process for a given timer at any point in 106time. When a timer for which a signal is still pending expires, no signal is 107queued, and a timer overrun will occur. When a timer expiration signal is 108accepted by a process, the 109.Fn timer_getoverrun 110function returns the timer expiration overrun count for the specified timer. 111The overrun count returned contains the number of extra timer expirations that 112occurred between the time the signal was generated (queued) and when it was 113accepted, up to but not including an maximum of {DELAYTIMER_MAX}. If the number of 114such extra expirations is greater than or equal to {DELAYTIMER_MAX}, then the 115overrun count is set to {DELAYTIMER_MAX}. The value returned by 116.Fn timer_getoverrun 117applies to the most recent expiration signal acceptance for the timer. If no 118expiration signal has been delivered for the timer, the return value of 119.Fn timer_getoverrun 120is unspecified. 121.Sh RETURN VALUES 122If the 123.Fn timer_getoverrun 124function succeeds, it returns the timer expiration overrun count as explained 125above. 126.Pp 127If the 128.Fn timer_gettime 129or 130.Fn timer_settime 131functions succeed, a value of 0 is returned. 132.Pp 133If an error occurs for any of these functions, the value -1 is returned, and 134errno set to indicate the error. 135.Sh ERRORS 136The 137.Fn timer_settime 138will fail if: 139.Bl -tag -width Er 140.It Bq Er EINVAL 141A value structure specified a nanosecond value less than zero or greater than 142or equal to 1000 million, and the it_value member of that structure did not 143specify zero seconds and nanoseconds. 144.El 145.Pp 146These functions may fail if: 147.Bl -tag -width Er 148.It Bq Er EINVAL 149The 150.Fa timerid 151argument does not correspond to an ID returned by 152.Fn timer_create 153but not yet deleted by 154.Fn timer_delete . 155.El 156.Pp 157The timer_settime() function may fail if: 158.Bl -tag -width Er 159.It Bq Er EINVAL 160The it_interval member of value is not zero and the timer was created with 161notification by creation of a new thread ( sigev_sigev_notify was SIGEV_THREAD) 162and a fixed stack address has been set in the thread attribute pointed to by 163sigev_notify_attributes. 164.El 165.Pp 166The 167.Fn timer_gettime 168and 169.Fn timer_settime 170may fail if: 171.Bl -tag -width Er 172.It Bq Er EFAULT 173Any arguments point outside the allocated address space or there is a 174memory protection fault. 175.El 176.Sh SEE ALSO 177.Xr clock_getres 2 , 178.Xr timer_create 2 179.Sh STANDARDS 180The 181.Fn timer_getoverrun , 182.Fn timer_gettime , 183and 184.Fn timer_settime 185function conform to 186.St -p1003.1-96 . 187