settimeofday(2) [netbsd man page]

GETTIMEOFDAY(2) 					      BSD 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 struc-
     ture 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.

     If the calling user is not the super-user, then the settimeofday() function 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 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.

     [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).

BSD
								   May 18, 2010 							       BSD

Check Out this Related Man Page

GETTIMEOFDAY(2) 					      BSD 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 *tp, struct timezone *tzp);

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

DESCRIPTION

     Note: timezone is no longer used; this information is kept outside the kernel.

     The system's notion of the current Greenwich time and the current time zone is obtained with the gettimeofday() system call, and set with the
     settimeofday() system 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 {
	     time_t	     tv_sec;	     /* seconds */
	     suseconds_t     tv_usec;	     /* and microseconds */
     };

     struct timezone {
	     int     tz_minuteswest; /* minutes west of Greenwich */
	     int     tz_dsttime;     /* type of dst correction */
     };

     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.

     Only the super-user may set the time of day or time zone.	If the system is running at securelevel >= 2 (see init(8)), the time may only be
     advanced or retarded by a maximum of one second.  This limitation is imposed to prevent a malicious super-user from setting arbitrary time
     stamps on files.  The system time can be adjusted backwards without restriction using the adjtime(2) system call even when the system is
     secure.

RETURN VALUES

     Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the
     error.

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

HISTORY

     The gettimeofday() system call appeared in 4.2BSD.

BSD
								   May 26, 1995 							       BSD

Linux and UNIX Man Pages

settimeofday(2) [netbsd man page]

Check Out this Related Man Page