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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.bugs.4bsd
Subject: Re: sendmail and others print bogus `Not a typewriter' errors
Message-ID: <8210@mimsy.UUCP>
Date: Thu, 27-Aug-87 19:55:58 EDT
Article-I.D.: mimsy.8210
Posted: Thu Aug 27 19:55:58 1987
Date-Received: Sat, 29-Aug-87 12:13:54 EDT
References: <8192@mimsy.UUCP> <6348@brl-smoke.ARPA>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 21

In article <6348@brl-smoke.ARPA> gwyn@brl-smoke.ARPA (Doug Gwyn ) writes:
>... The real problem is programmers who invoke perror() when errno is
>not guaranteed to be set up correctly to indicate an error cause.

Agreed.  Yet I think more section-3 routines should take care with
errno; in particular, those routines that can fail due to failing
system calls should arrange to set errno always upon failing.  For
instance,

	if ((f = fopen(tmp, "w")) == NULL) {
		perror("cannot create temp file");
		...

is technically wrong, but most often produces what is desired.  It
should always produce what is desired, or there should be a better
mechanism.  (A global error number is rather grotty.)  Restoring
errno inside isatty() is not a proper fix, but may help reduce
confusion until we get one.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris