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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 8.3 (Berkeley) 5/16/95 33.\" $FreeBSD: src/lib/libc/sys/getitimer.2,v 1.10.2.6 2001/12/14 18:34:00 ru Exp $ 34.\" 35.Dd May 16, 1995 36.Dt GETITIMER 2 37.Os 38.Sh NAME 39.Nm getitimer , 40.Nm setitimer 41.Nd get/set value of interval timer 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/time.h 46.Fd "#define ITIMER_REAL 0" 47.Fd "#define ITIMER_VIRTUAL 1" 48.Fd "#define ITIMER_PROF 2" 49.Ft int 50.Fn getitimer "int which" "struct itimerval *value" 51.Ft int 52.Fn setitimer "int which" "const struct itimerval *value" "struct itimerval *ovalue" 53.Sh DESCRIPTION 54The system provides each process with three interval timers, 55defined in 56.In sys/time.h . 57The 58.Fn getitimer 59call returns the current value for the timer specified in 60.Fa which 61in the structure at 62.Fa value . 63The 64.Fn setitimer 65call sets a timer to the specified 66.Fa value 67(returning the previous value of the timer if 68.Fa ovalue 69is non-nil). 70.Pp 71A timer value is defined by the 72.Fa itimerval 73structure: 74.Bd -literal -offset indent 75struct itimerval { 76 struct timeval it_interval; /* timer interval */ 77 struct timeval it_value; /* current value */ 78}; 79.Ed 80.Pp 81If 82.Fa it_value 83is non-zero, it indicates the time to the next timer expiration. 84If 85.Fa it_interval 86is non-zero, it specifies a value to be used in reloading 87.Fa it_value 88when the timer expires. 89Setting 90.Fa it_value 91to 0 disables a timer, regardless of the value of 92.Fa it_interval . 93Setting 94.Fa it_interval 95to 0 causes a timer to be disabled after its next expiration (assuming 96.Fa it_value 97is non-zero). 98.Pp 99Time values smaller than the resolution of the 100system clock are rounded up to this resolution 101(typically 10 milliseconds). 102.Pp 103The 104.Dv ITIMER_REAL 105timer decrements in real time. A 106.Dv SIGALRM 107signal is 108delivered when this timer expires. 109.Pp 110The 111.Dv ITIMER_VIRTUAL 112timer decrements in process virtual time. 113It runs only when the process is executing. A 114.Dv SIGVTALRM 115signal 116is delivered when it expires. 117.Pp 118The 119.Dv ITIMER_PROF 120timer decrements both in process virtual time and 121when the system is running on behalf of the process. It is designed 122to be used by interpreters in statistically profiling the execution 123of interpreted programs. 124Each time the 125.Dv ITIMER_PROF 126timer expires, the 127.Dv SIGPROF 128signal is 129delivered. Because this signal may interrupt in-progress 130system calls, programs using this timer must be prepared to 131restart interrupted system calls. 132.Pp 133The maximum number of seconds allowed for 134.Fa it_interval 135and 136.Fa it_value 137in 138.Fn setitimer 139is 100000000. 140.Sh NOTES 141Three macros for manipulating time values are defined in 142.In sys/time.h . 143.Fa Timerclear 144sets a time value to zero, 145.Fa timerisset 146tests if a time value is non-zero, and 147.Fa timercmp 148compares two time values. 149.Sh RETURN VALUES 150.Rv -std 151.Sh ERRORS 152.Fn Getitimer 153and 154.Fn setitimer 155will fail if: 156.Bl -tag -width Er 157.It Bq Er EFAULT 158The 159.Fa value 160parameter specified a bad address. 161.It Bq Er EINVAL 162A 163.Fa value 164parameter specified a time that was too large 165to be handled. 166.El 167.Sh SEE ALSO 168.Xr gettimeofday 2 , 169.Xr select 2 , 170.Xr sigaction 2 , 171.Xr clocks 7 172.Sh HISTORY 173The 174.Fn getitimer 175function call appeared in 176.Bx 4.2 . 177