Path: utzoo!utgpu!attcan!uunet!auspex!guy
From: guy@auspex.UUCP (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: lint question
Message-ID: <858@auspex.UUCP>
Date: 18 Jan 89 05:40:37 GMT
References: <491@babbage.acc.virginia.edu> <9322@smoke.BRL.MIL> <15024@cisunx.UUCP>
Reply-To: guy@auspex.UUCP (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 27

>Okay, so where does one find out what error codes are returned from these
>stdio functions?  The UNIX (AT&T 3B2) manuals I have say nothing in printf(3S)
>about error codes,

If by "error codes" you mean something like "errno" codes,
"printf"-family routines don't return them, but then *no* UNIX routine I
know of returns one - they all "return" them by setting "errno".  The
section 2 manual pages explicitly list values to which "errno" will be
set (although the lists are quite often incomplete); unfortunately, most
section 3 manual pages don't.  By and large, you can probably expect
that they can return any of the ones "read" or "write" can return
("write" in the case of "printf", for example), and that they *may*
return any of the others. 

If you mean "how can I test to see if they got an error *at all*,"
the AT&T 3B2 S5R3 manual says:

	Each function returns the number of characters transmitted (not
	counting the \0 in the case of "sprintf"), or a negative value
	if an output error is encountered.

in the first paragraph; perhaps earlier documentation didn't say this. 
The dpANS (or is it a pANS now?) says basically the same thing.  Some
older versions of UNIX, and some other versions of UNIX, or environments
within those vesrions, that maintain compatibility with those older
versions, have different return values (0 on success, -1 on error), but
over time those versions will most likely adopt the dpANS conventions.