gettimeofday(2)
NAME
gettimeofday, settimeofday − get/set date and time
SYNTAX
#include <sys/time.h>
gettimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
settimeofday(tp, tzp)
struct timeval *tp;
struct timezone *tzp;
DESCRIPTION
The 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.
The structures pointed to by tp and tzp are defined in <sys/time.h> as:
struct timeval {
u_longtv_sec;/* seconds since Jan. 1, 1970 */
longtv_usec;/* and microseconds */
};
struct timezone {
inttz_minuteswest;/* of Greenwich */
inttz_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 super-user may set the time of day.
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.
DIAGNOSTICS
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.