Portable versions of SCO Xenix/Unix nap() and rdchk()

[Doug Fields]

I am using the functions nap() and rdchk() in one of my programs.
I was wondering if anyone had any code to emulate these in a portable,
non-cpu intensive way. In case you don't know what these do:

  rdchk(f) - checks to see if a subsequent read would not block... I
             use it as rdchk(0) to see if the user has pressed a key
             yet. Returns 1 if there is input waiting.

  nap(t) - sleeps for t milliseconds. I use this to put a 1/5th of a
           second pause (nap(200)).

If there is no way to get nap() to work the program works just fine with
sleep(1) but it is a lot more slugish. As for rdchk, Apparently you can
use ioctl to set the VTIME and the other parameter to 0 and get a very
cpu-intensive form of rdchk.

Any help is appreiciated. Thanks.

Doug
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