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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: "usleep" routine in HP's
Message-ID: <17374@mimsy.UUCP>
Date: 8 May 89 14:46:05 GMT
References: <23340@shemp.CS.UCLA.EDU> <5740041@hpfcdc.HP.COM> <11215@bloom-beacon.MIT.EDU>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26

>In article <17358@mimsy.UUCP> I wrote:
>>If you have neither a 4.1-style `jobs library' nor 4.2-style signals,
>>you cannot implement sighold, sigpause, and sigrelse reliably.
>>
>>You cannot reliably implement select with anything other than poll().

In article <11215@bloom-beacon.MIT.EDU> adtaiwo@athena.mit.edu
(Ademola Taiwo) writes:
>Wait! That is not true. Emacs has implemented select, but only for
>read fds.

In other words, it has not implemented select.  (You also cannot get
read timeouts to work reliably.)

>There is ecsh, I believe it is the early CSH, correct me if
>I am wrong, but has Bill Joy written all over it. They implemented
>sigrelse, sigset and sigignore. The trick was to keep an array of all
>the available signals and later full around with them.

This is not reliable.

The key word is *reliable*; that was the whole point of the 4.1BSD
jobs library, and later the 4.2BSD reliable signals.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris