GETTIMEOFDAY(2) | System Calls Manual | GETTIMEOFDAY(2) |
gettimeofday
, settimeofday
—
#include <sys/time.h>
int
gettimeofday
(struct
timeval * restrict tp,
void * restrict tzp);
int
settimeofday
(const
struct timeval * restrict tp,
const void * restrict
tzp);
The system's notion of the current UTC time 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”.
If tp is NULL, the time will not be returned or set. Despite being declared void *, the objects pointed to by tzp shall be of type struct timezone.
The structures pointed to by tp and
tzp are defined in
<sys/time.h>
. The first one
is described in timeval(3)
and the latter legacy structure is defined as:
struct timezone { int tz_minuteswest; /* of Greenwich */ int tz_dsttime; /* type of dst correction to apply */ };
The timezone structure is provided only for
source compatibility. It is ignored by
settimeofday
(), and
gettimeofday
() will always return zeroes.
The settimeofday
() system call is
available only for the super-user. If the calling user is not the
super-user, the system call will fail, and the
settimeofday
() function in the standard C library
will try to use the
clockctl(4) device if
present, thus making it possible for non privileged users to set the system
time. If clockctl(4) is not
present or not accessible, then settimeofday
()
returns EPERM
.
gettimeofday
() function call appeared in
4.2BSD. The tzp argument was
deprecated in 4.4BSD (and many other systems).
December 8, 2015 | NetBSD 9.0 |