Can Unix sleep in terms of mili/micro?

[Sandeep Mehta]

  james at dlss2.UUCP (James Cummings) writes:

    TAYBENGH%NUSDISCS.BITNET at cunyvm.cuny.edu writes:
      >
      >        Can Unix sleep in terms of mili or mirco second? I am aware that
      >sleep() can only sleep in terms of second. Please specify the Unix Dialect
      >when u reply. Thanks.

	      How 'bout:

      sleep_less_than_sec(x)
      int x;
      {
	      int i;

	      for (i = 0;i <= x;i++)
		      ;
      }

For many (obvious) reasons a dummy loop is not the best idea. Besides
you may not have a real time clock in your UNIX box, e.g., Sun 3's (at
least the ones I use) use the Intersil 7170 "real-time" clock in 100 Hz
periodic mode, giving a resolution of only 10 milliseconds. Using the
clock(3C) function yields CPU time used only up to a 16.667 milliseconds
accuracy.  Sun 3 (SunOS 4.0) getrusage() assumes tick intervals of
20msec, for Sun 4's 10msec. I know that struct timerval' has a "usec"
field but of course the value is hardware dependent.

You might write your own little assembler routine to use a spare counter
or something (not advisable :-)) which will suffer from all the
restrictions of the process that uses it. I know that some folks @
Berkeley have a real-time timer facility for Sun 3's under SunOS and
it's (h'ware + s'ware) pretty cheap.  But then again, is UNIX/SunOS
real-time ?

Don't know if I answered the question either ? 

sandeep
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sxm at philabs.Philips.Com                  	"Jazz is Happiness" - Le Sony'Ra