Xref: utzoo comp.lang.c:30837 comp.unix.questions:24385
Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!ficc!peter
From: peter@ficc.ferranti.com (Peter da Silva)
Newsgroups: comp.lang.c,comp.unix.questions
Subject: Re: How do you tell if stdin/stdout is a terminal?
Keywords: stdin/stdout, unix, C, redirected I/O
Message-ID: <HT05KS8@xds13.ferranti.com>
Date: 6 Aug 90 20:08:44 GMT
References: <12210@hydra.gatech.EDU>
Reply-To: peter@ficc.ferranti.com (Peter da Silva)
Followup-To: comp.unix.questions
Organization: Xenix Support, FICC
Lines: 22

This is touched on in the latest FAQ for comp.unix.questions, under "how
do I tell if my program is running in the background". It is not a C
problem, but a UNIX problem. However, here are the answers.

In article <12210@hydra.gatech.EDU> gg10@prism.gatech.EDU (GALLOWAY) writes:
> If I have a program named "foo" which can accept standard input if no file
> name exists on the command line, and the user just types "foo", I want to
> display usage.

	if(isatty(fileno(stdin))) {
		usage();
		exit(0);
	}

> It would also be nice, if the output of "foo" was no ASCII to display a
> message like "foo: output must not be terminal".

	if(isatty(fileno(stdout))) {
		user_error();
		usage();
		exit(2);
	}
-- 
Peter da Silva.   `-_-'
+1 713 274 5180.   'U`
<peter@ficc.ferranti.com>