156 lines
4.7 KiB
Groff
156 lines
4.7 KiB
Groff
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.\" $NetBSD: gettimeofday.2,v 1.27 2010/05/18 07:14:18 jruoho Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95
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.\"
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.Dd May 18, 2010
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.Dt GETTIMEOFDAY 2
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.Os
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.Sh NAME
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.Nm gettimeofday ,
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.Nm settimeofday
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.Nd get/set date and time
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/time.h
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.Ft int
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.Fn gettimeofday "struct timeval * restrict tp" "void * restrict tzp"
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.Ft int
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.Fn settimeofday "const struct timeval * restrict tp" "const void * restrict tzp"
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.Sh DESCRIPTION
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.Bf -symbolic
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Note: time zone information is no longer provided by this interface.
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See
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.Xr localtime 3
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for information on how to retrieve it.
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.Ef
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.Pp
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The system's notion of the current UTC time is obtained with the
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.Fn gettimeofday
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call, and set with the
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.Fn settimeofday
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call.
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The time is expressed in seconds and microseconds
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since midnight (0 hour), January 1, 1970.
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The resolution of the system clock is hardware dependent,
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and the time may be updated continuously or in
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.Dq ticks .
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.Pp
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If
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.Fa tp
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is NULL, the time will not be returned or set.
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Despite being declared
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.Fa void * ,
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the objects pointed to by
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.Fa tzp
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shall be of type
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.Fa struct timezone .
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.Pp
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The structures pointed to by
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.Fa tp
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and
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.Fa tzp
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are defined in
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.In sys/time.h .
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The first one is described in
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.Xr timeval 3
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and the latter legacy structure is defined as:
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.Bd -literal -offset indent
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struct timezone {
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int tz_minuteswest; /* of Greenwich */
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int tz_dsttime; /* type of dst correction to apply */
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};
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.Ed
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.Pp
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The
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.Fa timezone
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structure is provided only for source compatibility.
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It is ignored by
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.Fn settimeofday ,
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and
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.Fn gettimeofday
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will always return zeroes.
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.Pp
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If the calling user is not the super-user, then the
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.Fn settimeofday
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function in the standard C library will try to use the
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.Xr clockctl 4
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device if present, thus making possible for non privileged users to
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set the system time.
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If
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.Xr clockctl 4
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is not present or not accessible, then
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.Fn settimeofday
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reverts to the
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.Fn settimeofday
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system call, which is restricted to the super user.
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.\" XXX uncomment when/if this is put into place!
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.\" If the system is running in secure mode (see
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.\" .Xr init 8 ),
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.\" the time may only be advanced.
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.\" This limitation is imposed to prevent a malicious super user
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.\" from setting arbitrary time stamps on files.
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.\" The system time can still be adjusted backwards using the
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.\" .Xr adjtime 2
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.\" system call even when the system is secure.
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.Sh RETURN VALUES
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A return value 0 indicates that the call succeeded.
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A return value \-1 indicates an error occurred, and in this
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case an error code is stored into the global variable
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.Va errno .
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.Sh ERRORS
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The following error codes may be set in
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.Va errno :
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.Bl -tag -width Er
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.It Bq Er EFAULT
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An argument address referenced invalid memory.
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.It Bq Er EPERM
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A user other than the super user attempted to set the time, or the specified
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time was less than the current time, which was not permitted at the current
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security level.
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.El
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.Sh SEE ALSO
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.Xr date 1 ,
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.Xr adjtime 2 ,
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.Xr ctime 3 ,
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.Xr localtime 3 ,
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.Xr clockctl 4 ,
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.Xr timed 8
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.Sh HISTORY
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The
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.Fn gettimeofday
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function call appeared in
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.Bx 4.2 .
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The
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.Fa tzp
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argument was deprecated in
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.Bx 4.4
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(and many other systems).
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