GETTIMEOFDAY(2)GETTIMEOFDAY(2)NAME
gettimeofday, settimeofday - get/set date and time
SYNOPSIS
#include <sys/time.h>
gettimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
settimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
DESCRIPTION
The system's notion of the current Greenwich time and the current time
zone is obtained with the gettimeofday call, and set with the
settimeofday call. The time is expressed in seconds and microseconds
since midnight (0 hour), January 1, 1970. The resolution of the system
clock is hardware dependent, and the time may be updated continuously
or in ``ticks.''
The structures pointed to by tp and tzp are defined in <sys/time.h> as:
struct timeval {
long tv_sec; /* seconds since Jan. 1, 1970 */
long tv_usec; /* and microseconds */
};
struct timezone {
int tz_minuteswest; /* of Greenwich */
int tz_dsttime; /* type of dst correction to apply */
};
The 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. Note, however, that the tzp argument is
ignored on the NeXT computer, which uses the /etc/tzone package
instead.
Only the super-user may set the time of day.
RETURN
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 errno.
ERRORS
The following error codes may be set in errno:
[EFAULT] An argument address referenced invalid memory.
[EPERM] A user other than the super-user attempted to set the
time.
SEE ALSOdate(1), adjtime(2), ctime(3), timed(8)4th Berkeley Distribution May 14, 1986 GETTIMEOFDAY(2)
