GETTIMEOFDAY(3C) Standard C Library Functions GETTIMEOFDAY(3C)
NAME
gettimeofday, settimeofday - get or set the date and time
SYNOPSIS
#include <sys/time.h>
int gettimeofday(
struct timeval *tp,
void *tzp);
int settimeofday(
struct timeval *tp,
void *tzp);
DESCRIPTION
The
gettimeofday() function gets and the
settimeofday() function sets
the system's notion of the current time. The current time is
expressed in elapsed seconds and microseconds since 00:00 Universal
Coordinated Time, January 1, 1970. The resolution of the system clock
is hardware dependent; the time may be updated continuously or in
clock ticks.
The
tp argument points to a
timeval structure, which includes the
following members:
long tv_sec; /* seconds since Jan. 1, 1970 */
long tv_usec; /* and microseconds */
If
tp is a null pointer, the current time information is not returned
or set.
The
TZ environment variable holds time zone information. See
TIMEZONE(5).
The
tzp argument to
gettimeofday() and
settimeofday() is ignored.
Only privileged processes can set the time of day.
RETURN VALUES
Upon successful completion,
0 is returned. Otherwise,
-1 is returned
and
errno is set to indicate the error.
ERRORS
The
settimeofday() function will fail if:
EINVAL The structure pointed to by
tp specifies an invalid time.
EPERM The {
PRIV_SYS_TIME} privilege was not asserted in the
effective set of the calling process.
The
gettimeofday() function will fail for 32-bit interfaces if:
EOVERFLOW The system time has progressed beyond 2038, thus the
size of the
tv_sec member of the
timeval structure
pointed to by
tp is insufficient to hold the current
time in seconds.
USAGE
If the
tv_usec member of
tp is > 500000,
settimeofday() rounds the
seconds upward. If the time needs to be set with better than one
second accuracy, call
settimeofday() for the seconds and then
adjtime(2) for finer accuracy.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------------------+
|Interface Stability |
gettimeofday() is Standard. |
+--------------------+-----------------------------+
|MT-Level | MT-Safe |
+--------------------+-----------------------------+
SEE ALSO
adjtime(2),
ctime(3C),
gethrtime(3C),
TIMEZONE(5),
attributes(7),
privileges(7),
standards(7) August 1, 2003 GETTIMEOFDAY(3C)
