GETTIMEOFDAY(2)                  System Calls                  GETTIMEOFDAY(2)




NAME

       gettimeofday, settimeofday - get/set date and time


SYNOPSIS

       #include <sys/time.h>

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

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


DESCRIPTION

       The  system's notion of the current Greenwich time and the current time
       zone is obtained with the gettimeofday call, and set with the  settime-
       ofday  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 or tzp is NULL, the associated time information  will
       not be returned or set.

       The structures pointed to by tp and tzp are defined in <sys/time.h> as:

       struct timeval {
            long tv_sec;        /* seconds since Jan. 1, 1970 */
            long tv_usec;  /* and microseconds */
       };

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

       The timezone structure indicates the local time zone (measured in  min-
       utes  of  time  westward  from Greenwich), and a flag that, if nonzero,
       indicates that Daylight Saving time applies locally during  the  appro-
       priate part of the year.

       Only the super-user may set the time of day or time zone.


RETURN

       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.


BUGS

       The GNO implementation does not set or make use of the time zone infor-
       mation pointed to by tzp, nor the tv_usec field.  The gettimeofday call
       always returns zero in the tv_usec field.


SEE ALSO

       date(1), adjtime(2), ctime(3), clocks(7), timed(8)


HISTORY

       The settimeofday function call appeared in 4.2BSD.



GNO                            19 December 1997                GETTIMEOFDAY(2)

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