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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.bugs.4bsd
Subject: Re: sendmail and others print bogus `Not a typewriter' errors
Message-ID: <6348@brl-smoke.ARPA>
Date: Thu, 27-Aug-87 14:59:49 EDT
Article-I.D.: brl-smok.6348
Posted: Thu Aug 27 14:59:49 1987
Date-Received: Sat, 29-Aug-87 10:31:06 EDT
References: <8192@mimsy.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 12

In article <8192@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>	Calls to isatty(), such as those in stdio, can clobber errno,
>	making later perror()s do strange things.

I take issue with this.  By no stretch of the imagination is this a
bug in isatty(); errno may always be set by successful functions, and
isatty() is always successful.

The real problem is programmers who invoke perror() when errno is
not guaranteed to be set up correctly to indicate an error cause.
By installing such a change in isatty(), you're encouraging this
misuse of perror().