settimeofday(2) - NetBSD Manual Pages

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GETTIMEOFDAY(2)           NetBSD System Calls Manual           GETTIMEOFDAY(2)


NAME

     gettimeofday, settimeofday -- get/set date and time


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/time.h>

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

     int
     settimeofday(const struct timeval * restrict tp,
         const void * restrict tzp);


DESCRIPTION

     Note: time zone information is no longer provided by this interface.  See
     localtime(3) for information on how to retrieve it.

     The system's notion of the current UTC time 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, the
     time will not be returned or set.  Despite being declared void *, the
     objects pointed to by tzp shall be of type struct timezone.

     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 is provided only for source compatibility.  It is
     ignored by settimeofday(), and gettimeofday() will always return zeroes.

     If the calling user is not the super-user, then the settimeofday() func-
     tion in the standard C library will try to use the clockctl(4) device if
     present, thus making possible for non privileged users to set the system
     time.  If clockctl(4) is not present or not accessible, then
     settimeofday() reverts to the settimeofday() system call, which is
     restricted to the super user.


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.


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, or the specified time was less than the current
                        time, which was not permitted at the current security
                        level.


SEE ALSO

     date(1), adjtime(2), ctime(3), localtime(3), clockctl(4), timed(8)


HISTORY

     The gettimeofday() function call appeared in 4.2BSD.  The tzp argument
     was deprecated in 4.4BSD (and many other systems).

NetBSD 3.1                     November 14, 2024                    NetBSD 3.1