Path: utzoo!utgpu!attcan!uunet!husc6!mailrus!purdue!decwrl!ucbvax!ernie.Berkeley.EDU!jas
From: jas@ernie.Berkeley.EDU (Jim Shankland)
Newsgroups: comp.lang.c
Subject: Re: Delay for a fraction of a second in C
Message-ID: <26678@ucbvax.BERKELEY.EDU>
Date: 3 Nov 88 23:21:11 GMT
References: <1145@orion.cf.uci.edu> <2804@ingr.UUCP>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: jas@ernie.Berkeley.EDU.UUCP (Jim Shankland)
Followup-To: comp.unix.questions
Organization: University of California, Berkeley
Lines: 19

In article <2804@ingr.UUCP> crossgl@ingr.UUCP (Gordon Cross) writes:
>You are not going to be able to do [sub-second sleeps] without coding
>up some kind of "delay loop" yourself....
>Remember that in the UNIX kernal, scheduled wakeups occur at fixed
>one second intervals.  Thus, unless you are using a non standard kernal, sleeps
>of only whole numbers of seconds are possible!

Never trust statements about the UNIX kernel from people who can't even
spell the word.  Kernel timeouts can occur at 1/HZ second intervals, where HZ
is typically 60 or 100.  The kernel CAN provide a system call to let
processes set alarms at that granularity -- BSD and derivatives do
(setitimer).  SysV-flavored systems just don't bother.  (Or is this
fixed in SysVR3?)

-----
Jim Shankland
jas@ernie.berkeley.edu

"The God I believe in isn't short of cash, MISTER!"