1.\" $NetBSD: getitimer.2,v 1.5 1995/02/27 12:33:00 cgd 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)getitimer.2 8.2 (Berkeley) 12/11/93 35.\" 36.Dd December 11, 1993 37.Dt GETITIMER 2 38.Os BSD 4.2 39.Sh NAME 40.Nm getitimer , 41.Nm setitimer 42.Nd get/set value of interval timer 43.Sh SYNOPSIS 44.Fd #include <sys/time.h> 45.Fd #define ITIMER_REAL 0 46.Fd #define ITIMER_VIRTUAL 1 47.Fd #define ITIMER_PROF 2 48.Ft int 49.Fn getitimer "int which" "struct itimerval *value" 50.Ft int 51.Fn setitimer "int which" "struct itimerval *value" "struct itimerval *ovalue" 52.Sh DESCRIPTION 53The system provides each process with three interval timers, 54defined in 55.Ao Pa sys/time.h Ac . 56The 57.Fn getitimer 58call returns the current value for the timer specified in 59.Fa which 60in the structure at 61.Fa value . 62The 63.Fn setitimer 64call sets a timer to the specified 65.Fa value 66(returning the previous value of the timer if 67.Fa ovalue 68is non-nil). 69.Pp 70A timer value is defined by the 71.Fa itimerval 72structure: 73.Bd -literal -offset indent 74struct itimerval { 75 struct timeval it_interval; /* timer interval */ 76 struct timeval it_value; /* current value */ 77}; 78.Ed 79.Pp 80If 81.Fa it_value 82is non-zero, it indicates the time to the next timer expiration. 83If 84.Fa it_interval 85is non-zero, it specifies a value to be used in reloading 86.Fa it_value 87when the timer expires. 88Setting 89.Fa it_value 90to 0 disables a timer. Setting 91.Fa it_interval 92to 0 causes a timer to be disabled after its next expiration (assuming 93.Fa it_value 94is non-zero). 95.Pp 96Time values smaller than the resolution of the 97system clock are rounded up to this resolution 98(typically 10 milliseconds). 99.Pp 100The 101.Dv ITIMER_REAL 102timer decrements in real time. A 103.Dv SIGALRM 104signal is 105delivered when this timer expires. 106.Pp 107The 108.Dv ITIMER_VIRTUAL 109timer decrements in process virtual time. 110It runs only when the process is executing. A 111.Dv SIGVTALRM 112signal 113is delivered when it expires. 114.Pp 115The 116.Dv ITIMER_PROF 117timer decrements both in process virtual time and 118when the system is running on behalf of the process. It is designed 119to be used by interpreters in statistically profiling the execution 120of interpreted programs. 121Each time the 122.Dv ITIMER_PROF 123timer expires, the 124.Dv SIGPROF 125signal is 126delivered. Because this signal may interrupt in-progress 127system calls, programs using this timer must be prepared to 128restart interrupted system calls. 129.Sh NOTES 130Three macros for manipulating time values are defined in 131.Ao Pa sys/time.h Ac . 132.Fa Timerclear 133sets a time value to zero, 134.Fa timerisset 135tests if a time value is non-zero, and 136.Fa timercmp 137compares two time values (beware that >= and <= do not 138work with this macro). 139.Sh RETURN VALUES 140If the calls succeed, a value of 0 is returned. If an error occurs, 141the value -1 is returned, and a more precise error code is placed 142in the global variable 143.Va errno . 144.Sh ERRORS 145.Fn Getitimer 146and 147.Fn setitimer 148will fail if: 149.Bl -tag -width Er 150.It Bq Er EFAULT 151The 152.Fa value 153parameter specified a bad address. 154.It Bq Er EINVAL 155A 156.Fa value 157parameter specified a time that was too large 158to be handled. 159.El 160.Sh SEE ALSO 161.Xr select 2 , 162.Xr sigaction 2 , 163.Xr gettimeofday 2 164.Sh HISTORY 165The 166.Fn getitimer 167function call appeared in 168.Bx 4.2 . 169