135 lines
4.3 KiB
Groff
135 lines
4.3 KiB
Groff
.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" $FreeBSD$
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.\"
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.Dd May 26, 1995
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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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.Fd #include <sys/time.h>
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.Ft int
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.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp"
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.Ft int
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.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp"
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.Sh DESCRIPTION
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.Bf -symbolic
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Note: timezone is no longer used; this information is kept outside
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the kernel.
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.Ef
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.Pp
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The system's notion of the current Greenwich time and the current time
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zone 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. The time is expressed in seconds and microseconds
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since midnight (0 hour), January 1, 1970. The resolution of the system
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clock is hardware dependent, and the time may be updated continuously or
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in
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.Dq ticks .
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If
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.Fa tp
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or
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.Fa tzp
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is NULL, the associated time
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information will not be returned or set.
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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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.Ao Pa sys/time.h Ac
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as:
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.Pp
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.Bd -literal
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struct timeval {
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long tv_sec; /* seconds since Jan. 1, 1970 */
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long tv_usec; /* and microseconds */
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};
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struct timezone {
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int tz_minuteswest; /* minutes west of Greenwich */
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int tz_dsttime; /* type of dst correction */
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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 indicates the local time zone
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(measured in minutes of time westward from Greenwich),
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and a flag that, if nonzero, indicates that
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Daylight Saving time applies locally during
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the appropriate part of the year.
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.Pp
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Only the super-user may set the time of day or time zone.
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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 0 return value indicates that the call succeeded.
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A -1 return value 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.
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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 clocks 7 ,
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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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