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.\" @(#)getitimer.2 6.6 (Berkeley) 3/10/91 33.\" 34.Dd March 10, 1991 35.Dt GETITIMER 2 36.Os BSD 4.2 37.Sh NAME 38.Nm getitimer , 39.Nm setitimer 40.Nd get/set value of interval timer 41.Sh SYNOPSIS 42.Fd #include <sys/time.h> 43.Fd #define ITIMER_REAL 0 44.Fd #define ITIMER_VIRTUAL 1 45.Fd #define ITIMER_PROF 2 46.Ft int 47.Fn getitimer "int which" "struct itimerval *value" 48.Ft int 49.Fn setitimer "int which" "struct itimerval *value" "struct itimerval *ovalue" 50.Sh DESCRIPTION 51The system provides each process with three interval timers, 52defined in 53.Ao Pa sys/time.h Ac . 54The 55.Fn getitimer 56call returns the current value for the timer specified in 57.Fa which 58in the structure at 59.Fa value . 60The 61.Fn setitimer 62call sets a timer to the specified 63.Fa value 64(returning the previous value of the timer if 65.Fa ovalue 66is non-nil). 67.Pp 68A timer value is defined by the 69.Fa itimerval 70structure: 71.Bd -literal -offset indent 72struct itimerval { 73 struct timeval it_interval; /* timer interval */ 74 struct timeval it_value; /* current value */ 75}; 76.Ed 77.Pp 78If 79.Fa it_value 80is non-zero, it indicates the time to the next timer expiration. 81If 82.Fa it_interval 83is non-zero, it specifies a value to be used in reloading 84.Fa it_value 85when the timer expires. 86Setting 87.Fa it_value 88to 0 disables a timer. Setting 89.Fa it_interval 90to 0 causes a timer to be disabled after its next expiration (assuming 91.Fa it_value 92is non-zero). 93.Pp 94Time values smaller than the resolution of the 95system clock are rounded up to this resolution 96(typically 10 milliseconds). 97.Pp 98The 99.Dv ITIMER_REAL 100timer decrements in real time. A 101.Dv SIGALRM 102signal is 103delivered when this timer expires. 104.Pp 105The 106.Dv ITIMER_VIRTUAL 107timer decrements in process virtual time. 108It runs only when the process is executing. A 109.Dv SIGVTALRM 110signal 111is delivered when it expires. 112.Pp 113The 114.Dv ITIMER_PROF 115timer decrements both in process virtual time and 116when the system is running on behalf of the process. It is designed 117to be used by interpreters in statistically profiling the execution 118of interpreted programs. 119Each time the 120.Dv ITIMER_PROF 121timer expires, the 122.Dv SIGPROF 123signal is 124delivered. Because this signal may interrupt in-progress 125system calls, programs using this timer must be prepared to 126restart interrupted system calls. 127.Sh NOTES 128Three macros for manipulating time values are defined in 129.Ao Pa sys/time.h Ac . 130.Fa Timerclear 131sets a time value to zero, 132.Fa timerisset 133tests if a time value is non-zero, and 134.Fa timercmp 135compares two time values (beware that >= and <= do not 136work with this macro). 137.Sh RETURN VALUES 138If the calls succeed, a value of 0 is returned. If an error occurs, 139the value -1 is returned, and a more precise error code is placed 140in the global variable 141.Va errno . 142.Sh ERRORS 143.Fn Getitimer 144and 145.Fn setitimer 146will 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 was too large 156to be handled. 157.El 158.Sh SEE ALSO 159.Xr select 2 , 160.Xr sigvec 2 , 161.Xr gettimeofday 2 162.Sh HISTORY 163The 164.Nm 165function call appeared in 166.Bx 4.2 . 167