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CLOCK_GETTIME(2)	 DragonFly System Calls Manual	      CLOCK_GETTIME(2)


clock_gettime, clock_settime, clock_getres -- get/set/calibrate date and time


Standard C Library (libc, -lc)


#include <sys/time.h> int clock_gettime(clockid_t clock_id, struct timespec *tp); int clock_settime(clockid_t clock_id, const struct timespec *tp); int clock_getres(clockid_t clock_id, struct timespec *tp);


The clock_gettime() and clock_settime() allow the calling process to retrieve or set the value used by a clock which is specified by clock_id. clock_id can be one of two values: CLOCK_REALTIME for time that incre- ments as a wall clock should and CLOCK_MONOTONIC for time that increments at a static rate in SI seconds. The structure pointed to by tp is defined in <sys/time.h> as: struct timespec { time_t tv_sec; /* seconds */ long tv_nsec; /* and nanoseconds */ }; Only the super-user may set the time of day. If the system securelevel is greater than 1 (see init(8)), the time may only be advanced. This limitation is imposed to prevent a malicious super-user from setting arbitrary time stamps on files. The system time can still be adjusted backwards using the adjtime(2) system call even when the system is secure. The resolution (granularity) of a clock is returned by the clock_getres() call. This value is placed in a (non-NULL) *tp.


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.


The following error codes may be set in errno: [EINVAL] The clock_id was not a valid value. [EFAULT] The *tp argument address referenced invalid memory. [EPERM] A user other than the super-user attempted to set the time.


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


The clock_gettime(), etc. functions conform to IEEE Std 1003.1b-1993 (``POSIX.1''). DragonFly 4.1 May 8, 1997 DragonFly 4.1