clock_gettime(2) - NetBSD Manual Pages

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CLOCK_SETTIME(2)          NetBSD System Calls Manual          CLOCK_SETTIME(2)


NAME

     clock_settime, clock_gettime, clock_getres -- clock and timer functions


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <time.h>

     int
     clock_settime(clockid_t clock_id, const struct timespec *tp);

     int
     clock_gettime(clockid_t clock_id, struct timespec *tp);

     int
     clock_getres(clockid_t clock_id, struct timespec *res);


DESCRIPTION

     The clock_settime() function sets the clock identified by clock_id to the
     absolute time specified by tp.  If the time specified by tp is not a mul-
     tiple of the resolution of the clock, tp is truncated to a multiple of
     the resolution.

     clock_gettime() function stores the time of the clock identified by
     clock_id into the location specified by tp.

     The clock_getres() function stores the resolution of the clock identified
     by clock_id into the location specified by res, unless res is NULL.

     A clock_id of CLOCK_REALTIME identifies the realtime clock for the sys-
     tem.  For this clock, the values specified by clock_settime() and
     obtained by clock_gettime() represent the amount of time (in seconds and
     nanoseconds) since 00:00 Universal Coordinated Time, January 1, 1970.

     A clock_id of CLOCK_MONOTONIC identifies a clock that increases at a
     steady rate (monotonically).  This clock is not affected by calls to
     adjtime(2) and settimeofday(2) and will fail with an EINVAL error if it's
     the clock specified in a call to clock_settime().  The origin of the
     clock is unspecified.

     If the calling user is not the super-user, then the clock_settime() 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
     clock_settime() reverts to the clock_settime() system call, which is
     restricted to the super user.


RETURN VALUES

     A value of 0 is returned on success.  Otherwise, a value of -1 is
     returned and errno is set to indicate the error.


ERRORS

     The clock_settime(), clock_gettime() and clock_getres() functions will
     fail if:

     [EINVAL]           The clock_id argument does not specify a known clock.

     [ENOSYS]           The function is not supported by this implementation.

     The clock_settime() function will fail if:

     [EINVAL]           The tp argument is outside the range for the specified
                        clock, clock_id.

     [EINVAL]           The tp argument specified a nanosecond value less than
                        zero of greater than or equal 1000 million.

     [EINVAL]           The clock_id argument is a clock that can not be
                        adjusted.

     [EPERM]            The calling process does not have the appropriate
                        privilege to set the specified clock, clock_id.

     The clock_gettime() function will fail if:

     [EFAULT]           The tp argument specifies an address that is not a
                        valid part of the process address space.


SEE ALSO

     ctime(3), time(3), clockctl(4)


STANDARDS

     The clock_settime(), clock_gettime() and clock_getres() functions conform
     to IEEE Std 1003.1b-1993 (``POSIX.1'').

NetBSD 5.2                     February 11, 1999                    NetBSD 5.2