gettimeofday(SSC)              6 January 1993              gettimeofday(SSC)


 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 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 tzp is zero, the time zone information will not be
    returned.

    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 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.  This argument is ignored on UNIX System V.

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

 Return

    A return value of zero indicates that the call succeeded.  A return value
    of -1 indicates that an error occurred, and in this case an error code is
    stored in the global variable errno.

 Errors

    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.

 See also

    date(C), adjtime(SSC), ctime(S), timed(ADMN) and xntpd(ADMN).