NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

     #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);

DESCRIPTION    [Toc]    [Back]

     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 four values: CLOCK_REALTIME for  time
that increments
  as  a  wall clock should, CLOCK_VIRTUAL for time that
increments only
     when the CPU is running in user mode on behalf of the  calling process,
     CLOCK_PROF  for time that increments when the CPU is running
in user or
     kernel mode, or CLOCK_MONOTONIC for time that increments  at
a steady rate
     (monotonically).

     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 superuser 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 superuser 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.

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     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 superuser attempted to set
the time.

SEE ALSO    [Toc]    [Back]

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

STANDARDS    [Toc]    [Back]

     The  clock_gettime(),  clock_settime(),  and  clock_setres()
functions conform
 to IEEE Std 1003.1b-1993 (``POSIX'').

OpenBSD      3.6                            May      8,      1997