Date: Sat, 08 Mar 2003 11:32:44 +0200
From: "Eli Zaretskii" <eliz AT elta DOT co DOT il>
Sender: halo1 AT zahav DOT net DOT il
To: rich AT phekda DOT freeserve DOT co DOT uk
Message-Id: <3028-Sat08Mar2003113243+0200-eliz@elta.co.il>
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CC: djgpp-workers AT delorie DOT com
In-reply-to: <3E6938EC.D9BFE2E4@phekda.freeserve.co.uk> (message from Richard
	Dawe on Sat, 08 Mar 2003 00:27:24 +0000)
Subject: Re: New POSIX: pwrite [PATCH]
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> Date: Sat, 08 Mar 2003 00:27:24 +0000
> From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
> 
> DJ Delorie wrote:
> [snip]
> > > +   /* Is this a redirected standard handle: stdout, stderr?
> > > +    * I.e.: are the standard handles pipes? Disallow on pipes. */
> > > +   switch(fd) {
> > > +   case STDOUT_FILENO:
> > > +   case STDERR_FILENO:
> > > +     if (isatty(fd) == 0) {
> > 
> > Why not just call isatty() for all fds?  stderr/stdout aren't the only
> > fds that can be redirected.  Consider that at least stdaux and stdprn
> > are also ttys.
> [snip]
> 
> But is there any easy way we can distinguish between pipes and (regular files,
> character devices)?

Wait a minute, there's something I missed when I looked at that code:
why do we need to disallow pwrite on redirected standard handles?
Redirected standard handles are just normal files on DOS/Windows, so
why should pwrite fail on them?

> With stdin, stdout, stderr we can assume they are pipes

You can't, really.  A redirected standard output could be a disk file,
as in "foo > bar".  What you are thinking about is "foo | bar", but
that doesn't have to be so, and we have no way of distinguishing
between these two possible uses of redirection.

> BTW stdaux and stdprn are not TTYs according to isatty(). Is this a bug?

No, I don't think so.  See my other mail in this thread.