PCLOCK(2)							     PCLOCK(2)

NAME    [Toc]    [Back]

     clock_settime, clock_gettime, clock_getres	- get/set date and time
     (POSIX)

C SYNOPSIS    [Toc]    [Back]

     #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    [Toc]    [Back]

     The clock_settime() function sets the specific clock, clock_id, to	the
     value specified by	tp. Time values	that are between two consecutive nonnegative
 integer multiples	of the resolution of the specified clock are
     truncated down to the smaller multiple of the resolution.

     The clock_gettime() function returns the current value tp for the
     specified clock, clock_id.	Depending on the clocks	resolution, it may be
     possible to obtain	the same time value with consecutive reads of the
     clock.  The time value may	also have a higher precision then the
     resolution	of the clock.

     The resolution of any clock can be	obtained by calling the	clock_getres()
     function. The resolution of the clock will	be returned in res. If res is
     NULL, then	the resolution of the clock will not be	returned.

CLOCKS    [Toc]    [Back]

     Supported clocks for clock_id are

     CLOCK_REALTIME The	system's notion	of the current time is obtained	with
		    this clock.	 The time is expressed in seconds and
		    nanoseconds	since midnight (00:00) Coordinated Universal
		    Time (UTC),	January	1, 1970.  The resolution for of	this
		    clock is never worse than 100 HZ (which equals 10
		    milliseconds).  The	actual resolution of the clock depends
		    on the timer capability of the underlying hardware(see
		    timers(5)).

     CLOCK_SGI_CYCLE
		    This clock allows easy access to the free running hardware
		    counter.  This SGI specific	clock maps the counter into
		    the	application address space and returns the current
		    value. Handling of the counter wraps on machines with
		    small counters is left to the application. To find the
		    number of bit the counter supports the application may
		    call syssgi() with the SGI_CYCLECNTR_SIZE request.	This
		    clock only is usable as a clock_id for the clock_gettime()
		    and	clock_getres() functions. This clock is	SGI specific
		    and	is not portable.





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PCLOCK(2)							     PCLOCK(2)



     CLOCK_SGI_FAST This clock has a higher resolution than CLOCK_REALTIME and
		    is available to privileged users only.  This clock only is
		    usable as a	clock_id. for the clock_getres() and
		    timer_create() functions. This clock is SGI	specific and
		    is not portable.

SEE ALSO    [Toc]    [Back]

     date(1), time(2), stime(2), ctime(3C), gettimeofday(3c),
     settimeofday(3c), and syssgi(2).

DIAGNOSTICS    [Toc]    [Back]

     The clock_settime(), clock_gettime(), and clock_getres() return a value
     of	0 to the calling process if the	operation is successful; otherwise the
     functions shall return a value of -1 and shall set	errno to indicate the
     error

     [EINVAL]	    The	clock_id argument is not a know	clock.

     The clock_settime() call also supports the	following values for errno

     [EINVAL]	    The	tp argument is outside the range for the given
		    clock_id , or the tp argument specified a nanosecond value
		    less then zero  or greater then or equal to	1000 million

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


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