GETTIMEOFDAY(2) BSD Programmer's Manual GETTIMEOFDAY(2)NAME
gettimeofday, settimeofday - get/set date and time
SYNOPSIS
#include <sys/time.h>
int
gettimeofday(struct timeval *tp, struct timezone *tzp);
int
settimeofday(const struct timeval *tp, const struct timezone *tzp);
DESCRIPTION
Note: timezone is no longer used; this information is kept outside the
kernel.
The system's notion of the current Greenwich time and the current time
zone is obtained with the gettimeofday() call, and set with the set-
timeofday() call. The time is expressed in seconds and microseconds since
the epoch, 00:00:00 seconds at midnight (0 hour), January 1, 1970, Temps
Atomique International (TAI). Leap seconds are counted, violating POSIX
but providing correct time. The resolution of the system clock is
hardware dependent, and the time may be updated continuously or in
"ticks". If tp or tzp is NULL, the associated time information will not
be returned or set.
The structures pointed to by tp and tzp are defined in <sys/time.h> as:
struct timeval {
time_t tv_sec; /* seconds since Jan. 1, 1970, 00:00:00 */
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.
Only the superuser may set the time of day or time zone. If the system
securelevel is greater than 1 (see init(8)), the time may only be ad-
vanced. This limitation is imposed to prevent a malicious superuser from
setting arbitrary time stamps on files. The system time can still be ad-
justed backwards using the adjtime(2) system call even when the system is
secure.
RETURN VALUES
A 0 return value indicates that the call succeeded. A -1 return value in-
dicates 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 superuser attempted to set the time.
SEE ALSOdate(1), adjtime(2), getitimer(2), ctime(3), timed(8)HISTORY
The gettimeofday() function call appeared in 4.2BSD. The tv_sec element
of struct timeval is of type time_t since MirOS #8.
MirOS BSD #10-current May 26, 1995 1
