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hardware clock

Posted on 2000-03-17
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How can I get the hardwarr clock in my c++ program beneath Solaris 2.5.1/2.6? Is there any API? What is the difference between clock_settime(), gettimeofday() and time()? How precicious are them? I want to get to it because I would take it as the time base in my system.Thank you!
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Question by:peak_chen
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by:jlevie
ID: 2630421
Why would you want to get to the hardware clock?
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by:peak_chen
ID: 2630824
Edited text of question.
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by:jlevie
ID: 2631426
I guess I didn't make my query very clear. Why the hardware clock as opposed to gettimeofday(). If the sytem is set up to time sync via NTP (Network Time Protocol), I believe that the system call is usually more accurate as the hardware clock isn't necessarily updated as often. And I'd have to check to be certain, but I think the hardware clock only has a resolution of 1 sec. The system clock does a bit better as it counts clock ticks.
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chris_calabrese earned 45 total points
ID: 2637947
The hardware clock on most modern SPARC systems counts clock ticks since system bootup in (I think) miliseconds.  This isn't very useful and you can only access it from inside the kernel.

clock_settime() and clock_gettime() are the low level timer routines that wrap the hardware clock in a nice API for handling multiple timers, and converting everything to nanoseconds.  This is the closest you can get to the hardware clock under Solaris.

gettimeofday() is similar to cloc_gettime(CLOCK_REALTIME, ), but with maximum resolution of microseconds (not much of an issue in Solaris, where the hardware clock isn't more accurate than this and there's system call overhead, etc. that skews things even more).

time() is similar to gettimeofday(), but with maximum resolution of one second.
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