gettimeofday(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>.  The
     first one is described in timeval(3) and the latter legacy structure is
     defined as:

           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.

     The settimeofday() system call is available only for the super-user.  If
     the calling user is not the super-user, the system call will fail, and
     the settimeofday() function in the standard C library will try to use the
     clockctl(4) device if present, thus making it possible for non privileged
     users to set the system time.  If clockctl(4) is not present or not
     accessible, then settimeofday() returns EPERM.


RETURN VALUES

     A return value 0 indicates that the call succeeded.  A return value -1
     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.

     [EINVAL]           settimeofday(): tp.tv_sec is outside the range
                        [0..2^36] or tp.tv_usec is outside the range
                        [0..999,999].

     [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 10.99                   October 16, 2022                   NetBSD 10.99