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From: rsalz@bbn.com (Rich Salz)
Newsgroups: comp.lang.c
Subject: Re: Question on ANSI C compatibility (really return values and errno)
Message-ID: <244@papaya.bbn.com>
Date: Thu, 19-Nov-87 17:23:54 EST
Article-I.D.: papaya.244
Posted: Thu Nov 19 17:23:54 1987
Date-Received: Sun, 22-Nov-87 08:33:35 EST
References: <10224@brl-adm.ARPA> <9272@mimsy.UUCP> <1804@geac.UUCP> <1761@haddock.ISC.COM>
Reply-To: rsalz@bbn.com (Rich Salz)
Organization: BBN Laboratories, Cambridge MA
Lines: 15
Summary: Can't check errno unless syscall fails

>This code is correct, but unavoidably generates a lint warning (though it can
>be silenced with a (void) cast):
>  errno = 0;
>  unlink(fname);
>  if (errno != 0) abort();
Nope.  You're not "allowed" (sic) to check errno unless you know that
the call really failed.  That is:
	if (unlink(fname) < 0 && errno == ENOPERM) perror("Try 'su'"), exit(1);
is legal, albeit gross, code.

I'll now step aside, and watch this degenerate into another isatty()/perror/
"not a typewriter" mudslide...
	/r$
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