200 lines
5.2 KiB
Groff
200 lines
5.2 KiB
Groff
.\" $NetBSD: getitimer.2,v 1.28 2011/10/27 16:10:37 christos Exp $
|
|
.\"
|
|
.\" 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. 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 8.3 (Berkeley) 5/16/95
|
|
.\"
|
|
.Dd October 27, 2011
|
|
.Dt GETITIMER 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm getitimer ,
|
|
.Nm setitimer
|
|
.Nd get/set value of interval timer
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/time.h
|
|
.Ft int
|
|
.Fn getitimer "int which" "struct itimerval *value"
|
|
.Ft int
|
|
.Fn setitimer "int which" "const struct itimerval * restrict value" "struct itimerval * restrict 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 not
|
|
.Dv NULL .
|
|
.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
|
|
The
|
|
.Fa which
|
|
parameter specifies the type of the timer:
|
|
.Bl -tag -width "ITIMER_MONOTONIC " -offset indent
|
|
.It Dv ITIMER_REAL
|
|
timer decrements in real time.
|
|
This timer is affected by
|
|
.Xr adjtime 2
|
|
and
|
|
.Xr settimeofday 2 .
|
|
A
|
|
.Dv SIGALRM
|
|
signal is
|
|
delivered when this timer expires.
|
|
.It 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.
|
|
.It 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.
|
|
.It Dv ITIMER_MONOTONIC
|
|
timer decrements in monotonic time.
|
|
This timer is not affected by
|
|
.Xr adjtime 2
|
|
and
|
|
.Xr settimeofday 2 .
|
|
A
|
|
.Dv SIGALRM
|
|
signal is
|
|
delivered when this timer expires.
|
|
.El
|
|
Note that:
|
|
.Bl -bullet -offset indent
|
|
.It
|
|
Time values smaller than the resolution of the
|
|
system clock are rounded up to this resolution
|
|
(typically 10 milliseconds).
|
|
.It
|
|
The interaction between
|
|
.Fn setitimer
|
|
and
|
|
.Xr alarm 3
|
|
or
|
|
.Xr sleep 3
|
|
is unspecified by the specification.
|
|
.El
|
|
.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
|
|
Both functions may fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EFAULT
|
|
The
|
|
.Fa value
|
|
parameter specified a bad address.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa which
|
|
parameter was not a known timer type, or the
|
|
.Fa value
|
|
parameter specified a time that was too large
|
|
to be handled.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr gettimeofday 2 ,
|
|
.Xr select 2 ,
|
|
.Xr sigaction 2 ,
|
|
.Xr itimerval 3 ,
|
|
.Xr timeradd 3
|
|
.Sh STANDARDS
|
|
The functions conform to
|
|
.St -p1003.1-2001 .
|
|
The later
|
|
.St -p1003.1-2008
|
|
revision however marked both as obsolescent,
|
|
recommending the use of
|
|
.Xr timer_gettime 2
|
|
and
|
|
.Xr timer_settime 2
|
|
instead.
|
|
.Sh HISTORY
|
|
The
|
|
.Fn getitimer
|
|
function call appeared in
|
|
.Bx 4.2 .
|
|
The
|
|
.Dv ITIMER_MONOTONIC
|
|
functionality appeared in
|
|
.Nx 6.0 .
|