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GETTIMEOFDAY(2)             BSD System Calls Manual            GETTIMEOFDAY(2)

     gettimeofday, settimeofday -- get/set date and time

     #include <sys/time.h>

     gettimeofday(struct timeval *restrict tp, void *restrict tzp);

     settimeofday(const struct timeval *tp, const struct timezone *tzp);

     The system's notion of the current Greenwich time and the current time zone 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 and tzp is non-NULL, nonNULL,
     NULL, gettimeofday() will populate the timezone struct in tzp.  If tp is non-NULL and tzp is NULL, then
     only the timeval struct in tp is populated. If both tp and tzp are NULL, nothing is returned.

     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 */
             suseconds_t  tv_usec;  /* and microseconds */

     struct timezone {
             int     tz_minuteswest; /* of Greenwich */
             int     tz_dsttime;     /* type of dst correction to apply */

     The timeval structure specifies a time value in seconds and microseconds.  The values in timeval are
     opaque types whose length may vary on different machines; depending on them to have any given length
     may lead to errors.

     The timezone structure indicates the local time zone (measured in minutes of time westward from Green-wich), Greenwich),
     wich), 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 or time zone.  If the system securelevel is greater than 1
     (see init(8) ), the time may only be advanced.  This limitation is imposed to prevent a malicious
     super-user from setting arbitrary time stamps on files.  The system time can still be adjusted back-wards backwards
     wards using the adjtime(2) system call even when the system is secure.

     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.

     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.

     #include <sys/time.h>

     gettimeofday(struct timeval *tp, struct timezone *tzp);

     The type of tzp has changed.

     date(1), adjtime(2), ctime(3), compat(5), timed(8)

     The gettimeofday() function call appeared in 4.2BSD.

4th Berkeley Distribution       August 5, 2008       4th Berkeley Distribution

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