Message-ID: <3E0F0CAE.CC28815F@yahoo.com>
From: CBFalconer <cbfalconer AT yahoo DOT com>
Organization: Ched Research
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: Detecting stdin not redirected
References: <3E0EA6CF DOT 51896D97 AT yahoo DOT com> <3E0EDC94 DOT 421FD75E AT phekda DOT freeserve DOT co DOT uk>
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Date: Sun, 29 Dec 2002 14:55:07 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Richard Dawe wrote:
> CBFalconer wrote:
> 
> > With gcc and DJGPP, how can a running program detect that stdin
> > has not been redirected from the keyboard?  How portable is such a
> > method, i.e. will it hold up for Linux?  To allow for use of
> > external terminals, I guess the thing wanted is to detect that
> > stdin is actually a disk file (or a pipe) as opposed to a device.
> [snip]
> 
> Take a look at isatty:
> 
>     info libc alpha isatty

That looks promising, except it needs an int file descriptor. 

After a little research in stdio.h I conclude that "fileno(fp)" is
required.  So I need to work with "if (isatty(fileno(stdin)))" and
that should cover the portability area.  Thanks, that did it.

I want this for a class of filters that normally shut up, but give
help if run with no redirection.

-- 
Chuck F (cbfalconer AT yahoo DOT com) (cbfalconer AT worldnet DOT att DOT net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>  USE worldnet address!