gettimeofday.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 77 行

.\" SCCSID: @(#)gettimeofday.2	8.1	9/11/90
.TH gettimeofday 2
.SH Name
gettimeofday, settimeofday \- get or set date and time
.SH Syntax
.nf
.ft B
#include <sys/time.h>
.PP
.ft B
gettimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
.PP
.ft B
settimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
.fi
.SH Description
.NXR "gettimeofday system call"
.NXR "settimeofday system call"
.NXA "gettimeofday system call" "stime system call"
.NXR "time" "getting"
.NXR "time" "setting"
The
.PN gettimeofday
system call
returns the system's notion of the current Greenwich time and
the current time zone.  Time returned is expressed relative
in seconds and microseconds since midnight January 1, 1970.
.PP
The structures pointed to by
.I tp
and
.I tzp
are defined in <sys/time.h>
as:
.PP
.EX
struct timeval {
	long	tv_sec;		/* seconds since Jan. 1, 1970 */
	long	tv_usec;	/* and microseconds */
};
.sp 1
struct timezone {
	int	tz_minuteswest;	/* of Greenwich */
	int	tz_dsttime;	/* type of dst correction to apply */
};
.EE
.PP
The 
.I timezone
structure indicates the local time zone
(measured in minutes of time westward from Greenwich),
and a flag that, if nonzero, indicates that
Daylight Saving time applies locally during
the appropriate part of the year.
.PP
Only the superuser can set the time of day.
.SH Return Values
A 0 return value indicates that the call succeeded.
A \-1 return value indicates an error occurred, and in this
case an error code is stored into the global variable \fIerrno\fP.
.SH Diagnostics
The 
.PN gettimeofday
call fails under the following conditions:
.TP 15
[EFAULT]
An argument address referenced invalid memory.
.TP 15
[EPERM]
A user other than the superuser attempted to set the time.
.SH See Also
date(1), stime(2), ctime(3)