From: Daniel Berger <Daniel.Berger@...>
Date: 2005-10-25T05:29:02+09:00
Subject: Re: $stderr.reopen bug?

Tanner Burson wrote:
> Hi,
> I'm working through what seems like it should be a simple operation,
> re-routing STDERR to point elsewhere. I can do the following
> 
> $stderr.reopen("/dev/null")
> 
> which works fine. But what I'd like to do is capture that output, so I
> figured StringIO would be the way to go. According to the docs for IO#reopen
> it can take an IO object as it's only parameter, and use that to re-open,
> but when I do the following
> 
> require 'stringio'
> str_io = StringIO.new
> $stderr.reopen(str_io)
> 
> I get
> 
> TypeError: can't convert StringIO into String
> 
> any ideas? Is the documentation just wrong, and it can only take a string
> arg? Or will it take only a File IO object?

You'll need an IO object because, behind the scenes, IO.reopen grabs the fileno 
from the object and uses the dup2() function (at least, on *nix).

The StringIO#fileno method exists, but returns nil, since there is no 
associated fileno with a StringIO object.  Actually, I don't even think it gets 
that far.  I suspect it's choking on the rb_io_get_io() internal function.

Whether or not this could be made to work with StringIO, I'm not sure.

Regards,

Dan