1.\" $NetBSD: getitimer.2,v 1.26 2011/05/02 17:14:20 jruoho Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)getitimer.2 8.3 (Berkeley) 5/16/95 31.\" 32.Dd May 2, 2011 33.Dt GETITIMER 2 34.Os 35.Sh NAME 36.Nm getitimer , 37.Nm setitimer 38.Nd get/set value of interval timer 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/time.h 43.Ft int 44.Fn getitimer "int which" "struct itimerval *value" 45.Ft int 46.Fn setitimer "int which" "const struct itimerval * restrict value" "struct itimerval * restrict ovalue" 47.Sh DESCRIPTION 48The system provides each process with three interval timers, 49defined in 50.Ao Pa sys/time.h Ac . 51The 52.Fn getitimer 53call returns the current value for the timer specified in 54.Fa which 55in the structure at 56.Fa value . 57The 58.Fn setitimer 59call sets a timer to the specified 60.Fa value , 61returning the previous value of the timer if 62.Fa ovalue 63is not 64.Dv NULL . 65.Pp 66A timer value is defined by the 67.Fa itimerval 68structure: 69.Bd -literal -offset indent 70struct itimerval { 71 struct timeval it_interval; /* timer interval */ 72 struct timeval it_value; /* current value */ 73}; 74.Ed 75.Pp 76If 77.Fa it_value 78is non-zero, it indicates the time to the next timer expiration. 79If 80.Fa it_interval 81is non-zero, it specifies a value to be used in reloading 82.Fa it_value 83when the timer expires. 84Setting 85.Fa it_value 86to 0 disables a timer. 87Setting 88.Fa it_interval 89to 0 causes a timer to be disabled after its next expiration (assuming 90.Fa it_value 91is non-zero). 92.Pp 93The 94.Fa which 95parameter specifies the type of the timer: 96.Bl -tag -width "ITIMER_VIRTUAL " -offset indent 97.It Dv ITIMER_REAL 98timer decrements in real time. 99A 100.Dv SIGALRM 101signal is 102delivered when this timer expires. 103.It Dv ITIMER_VIRTUAL 104timer decrements in process virtual time. 105It runs only when the process is executing. 106A 107.Dv SIGVTALRM 108signal 109is delivered when it expires. 110.It Dv ITIMER_PROF 111timer decrements both in process virtual time and 112when the system is running on behalf of the process. 113It is designed to be used by interpreters in statistically profiling 114the execution of interpreted programs. 115Each time the 116.Dv ITIMER_PROF 117timer expires, the 118.Dv SIGPROF 119signal is 120delivered. 121Because this signal may interrupt in-progress 122system calls, programs using this timer must be prepared to 123restart interrupted system calls. 124.El 125Note that: 126.Bl -bullet -offset indent 127.It 128Time values smaller than the resolution of the 129system clock are rounded up to this resolution 130(typically 10 milliseconds). 131.It 132The interaction between 133.Fn setitimer 134and 135.Xr alarm 3 136or 137.Xr sleep 3 138is unspecified by the specification. 139.El 140.Sh RETURN VALUES 141If the calls succeed, a value of 0 is returned. 142If an error occurs, the value \-1 is returned, and a more precise error 143code is placed in the global variable 144.Va errno . 145.Sh ERRORS 146Both functions may fail if: 147.Bl -tag -width Er 148.It Bq Er EFAULT 149The 150.Fa value 151parameter specified a bad address. 152.It Bq Er EINVAL 153A 154.Fa value 155parameter specified a time that was too large 156to be handled. 157.El 158.Sh SEE ALSO 159.Xr gettimeofday 2 , 160.Xr select 2 , 161.Xr sigaction 2 , 162.Xr itimerval 3 , 163.Xr timeradd 3 164.Sh STANDARDS 165The functions conform to 166.St -p1003.1-2001 . 167The later 168.St -p1003.1-2008 169revision however marked both as obsolescent, 170recommending the use of 171.Xr timer_gettime 2 172and 173.Xr timer_settime 2 174instead. 175.Sh HISTORY 176The 177.Fn getitimer 178function call appeared in 179.Bx 4.2 . 180