1.\" Copyright (c) 1983, 1991 The Regents of the University of California. 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, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" from: @(#)getitimer.2 6.6 (Berkeley) 3/10/91 33.\" $Id: getitimer.2,v 1.3 1993/11/25 00:38:54 jtc Exp $ 34.\" 35.Dd March 10, 1991 36.Dt GETITIMER 2 37.Os BSD 4.2 38.Sh NAME 39.Nm getitimer , 40.Nm setitimer 41.Nd get/set value of interval timer 42.Sh SYNOPSIS 43.Fd #include <sys/time.h> 44.Fd #define ITIMER_REAL 0 45.Fd #define ITIMER_VIRTUAL 1 46.Fd #define ITIMER_PROF 2 47.Ft int 48.Fn getitimer "int which" "struct itimerval *value" 49.Ft int 50.Fn setitimer "int which" "struct itimerval *value" "struct itimerval *ovalue" 51.Sh DESCRIPTION 52The system provides each process with three interval timers, 53defined in 54.Ao Pa sys/time.h Ac . 55The 56.Fn getitimer 57call returns the current value for the timer specified in 58.Fa which 59in the structure at 60.Fa value . 61The 62.Fn setitimer 63call sets a timer to the specified 64.Fa value 65(returning the previous value of the timer if 66.Fa ovalue 67is non-nil). 68.Pp 69A timer value is defined by the 70.Fa itimerval 71structure: 72.Bd -literal -offset indent 73struct itimerval { 74 struct timeval it_interval; /* timer interval */ 75 struct timeval it_value; /* current value */ 76}; 77.Ed 78.Pp 79If 80.Fa it_value 81is non-zero, it indicates the time to the next timer expiration. 82If 83.Fa it_interval 84is non-zero, it specifies a value to be used in reloading 85.Fa it_value 86when the timer expires. 87Setting 88.Fa it_value 89to 0 disables a timer. Setting 90.Fa it_interval 91to 0 causes a timer to be disabled after its next expiration (assuming 92.Fa it_value 93is non-zero). 94.Pp 95Time values smaller than the resolution of the 96system clock are rounded up to this resolution 97(typically 10 milliseconds). 98.Pp 99The 100.Dv ITIMER_REAL 101timer decrements in real time. A 102.Dv SIGALRM 103signal is 104delivered when this timer expires. 105.Pp 106The 107.Dv ITIMER_VIRTUAL 108timer decrements in process virtual time. 109It runs only when the process is executing. A 110.Dv SIGVTALRM 111signal 112is delivered when it expires. 113.Pp 114The 115.Dv ITIMER_PROF 116timer decrements both in process virtual time and 117when the system is running on behalf of the process. It is designed 118to be used by interpreters in statistically profiling the execution 119of interpreted programs. 120Each time the 121.Dv ITIMER_PROF 122timer expires, the 123.Dv SIGPROF 124signal is 125delivered. Because this signal may interrupt in-progress 126system calls, programs using this timer must be prepared to 127restart interrupted system calls. 128.Sh NOTES 129Three macros for manipulating time values are defined in 130.Ao Pa sys/time.h Ac . 131.Fa Timerclear 132sets a time value to zero, 133.Fa timerisset 134tests if a time value is non-zero, and 135.Fa timercmp 136compares two time values (beware that >= and <= do not 137work with this macro). 138.Sh RETURN VALUES 139If the calls succeed, a value of 0 is returned. If an error occurs, 140the value -1 is returned, and a more precise error code is placed 141in the global variable 142.Va errno . 143.Sh ERRORS 144.Fn Getitimer 145and 146.Fn setitimer 147will fail if: 148.Bl -tag -width Er 149.It Bq Er EFAULT 150The 151.Fa value 152parameter specified a bad address. 153.It Bq Er EINVAL 154A 155.Fa value 156parameter specified a time was too large 157to be handled. 158.El 159.Sh SEE ALSO 160.Xr select 2 , 161.Xr sigvec 2 , 162.Xr gettimeofday 2 163.Sh HISTORY 164The 165.Fn getitimer 166function call appeared in 167.Bx 4.2 . 168