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Diffstat (limited to 'lib/libc/sys/getitimer.2')
| -rw-r--r-- | lib/libc/sys/getitimer.2 | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/lib/libc/sys/getitimer.2 b/lib/libc/sys/getitimer.2 new file mode 100644 index 0000000..ac2e59a --- /dev/null +++ b/lib/libc/sys/getitimer.2 @@ -0,0 +1,166 @@ +.\" Copyright (c) 1983, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)getitimer.2 8.2 (Berkeley) 12/11/93 +.\" +.Dd December 11, 1993 +.Dt GETITIMER 2 +.Os BSD 4.2 +.Sh NAME +.Nm getitimer , +.Nm setitimer +.Nd get/set value of interval timer +.Sh SYNOPSIS +.Fd #include <sys/time.h> +.Fd #define ITIMER_REAL 0 +.Fd #define ITIMER_VIRTUAL 1 +.Fd #define ITIMER_PROF 2 +.Ft int +.Fn getitimer "int which" "struct itimerval *value" +.Ft int +.Fn setitimer "int which" "struct itimerval *value" "struct itimerval *ovalue" +.Sh DESCRIPTION +The system provides each process with three interval timers, +defined in +.Ao Pa sys/time.h Ac . +The +.Fn getitimer +call returns the current value for the timer specified in +.Fa which +in the structure at +.Fa value . +The +.Fn setitimer +call sets a timer to the specified +.Fa value +(returning the previous value of the timer if +.Fa ovalue +is non-nil). +.Pp +A timer value is defined by the +.Fa itimerval +structure: +.Bd -literal -offset indent +struct itimerval { + struct timeval it_interval; /* timer interval */ + struct timeval it_value; /* current value */ +}; +.Ed +.Pp +If +.Fa it_value +is non-zero, it indicates the time to the next timer expiration. +If +.Fa it_interval +is non-zero, it specifies a value to be used in reloading +.Fa it_value +when the timer expires. +Setting +.Fa it_value +to 0 disables a timer. Setting +.Fa it_interval +to 0 causes a timer to be disabled after its next expiration (assuming +.Fa it_value +is non-zero). +.Pp +Time values smaller than the resolution of the +system clock are rounded up to this resolution +(typically 10 milliseconds). +.Pp +The +.Dv ITIMER_REAL +timer decrements in real time. A +.Dv SIGALRM +signal is +delivered when this timer expires. +.Pp +The +.Dv ITIMER_VIRTUAL +timer decrements in process virtual time. +It runs only when the process is executing. A +.Dv SIGVTALRM +signal +is delivered when it expires. +.Pp +The +.Dv ITIMER_PROF +timer decrements both in process virtual time and +when the system is running on behalf of the process. It is designed +to be used by interpreters in statistically profiling the execution +of interpreted programs. +Each time the +.Dv ITIMER_PROF +timer expires, the +.Dv SIGPROF +signal is +delivered. Because this signal may interrupt in-progress +system calls, programs using this timer must be prepared to +restart interrupted system calls. +.Sh NOTES +Three macros for manipulating time values are defined in +.Ao Pa sys/time.h Ac . +.Fa Timerclear +sets a time value to zero, +.Fa timerisset +tests if a time value is non-zero, and +.Fa timercmp +compares two time values (beware that >= and <= do not +work with this macro). +.Sh RETURN VALUES +If the calls succeed, a value of 0 is returned. If an error occurs, +the value -1 is returned, and a more precise error code is placed +in the global variable +.Va errno . +.Sh ERRORS +.Fn Getitimer +and +.Fn setitimer +will fail if: +.Bl -tag -width Er +.It Bq Er EFAULT +The +.Fa value +parameter specified a bad address. +.It Bq Er EINVAL +A +.Fa value +parameter specified a time that was too large +to be handled. +.El +.Sh SEE ALSO +.Xr select 2 , +.Xr sigvec 2 , +.Xr gettimeofday 2 +.Sh HISTORY +The +.Nm +function call appeared in +.Bx 4.2 . |
