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From: Ben Morrow on 6 Jul 2010 06:46

Quoth Ilya Zakharevich <nospam-abuse(a)ilyaz.org>:
> On 2010-07-05, Ben Morrow <ben(a)morrow.me.uk> wrote:
> >> > If (the Perl-level) STDERR is currently closed, warn will write its
> >> > output to (the C-level) stderr, which means fd 2.
> >>
> >> It is THIS behaviour which causes unexpected results. Is it
> >> documented anywhere?
>
> > I don't know. I don't think so.
>
> Which does not make the behaviour less puzzling...

Well, it's kind-of a last ditch effort to send the error message
*somewhere* sensible. Perl perhaps ought to prevent you from closing
these three fds altogether (or rather, implicitly reopen them to
/dev/null if you close them) and make sure they stay permanently
attached to their proper filehandles.

> [ I note that I have seen this behaviour explicitly mentioned on p5p
> in 90s. But at that time I did not realize how puzzling this
> behaviour may be. ]
>
> BTW, is there any backdoor way to redirect STDERR to some other fd
> than 2?

Oh, that's easy:

close STDERR; close STDIN;
open STDERR, ">", "/dev/tty";
open STDIN, "<", "/dev/tty";

You now have STDIN on fd 2 and STDERR on fd 0. Since STDERR is now open,
error messages will go out of fd 0.

Ben

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