gettimeofday(2)
Name
gettimeofday, settimeofday − get or 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 {
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 superuser can set the time of day.
Return Values
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 gettimeofday call fails under the following conditions:
[EFAULT] An argument address referenced invalid memory.
[EPERM] A user other than the superuser attempted to set the time.