Forgive me if I don't explain this fully (I'm far from an expert), but the
reason ^] works in telnet is because it is a tty. Telnet calls an ioctl on
its stdout that causes ^] to have special meaning, and later make telnet
return from a select() to hand out the telnet> prompt. ioctl doesn't work on
any files, just "character special files" according to the manpage. When you
use popen the ioctl fails because you're not calling it on a terminal,
you're calling it on a regular pipe. 

So basically if you want that behavior you need to put it through a
terminal, because the ioctl is what makes that happen and the ioctl requires
a terminal.

On Tue, Jun 22, 2004 at 02:52:59PM +0900, Hal Fulton wrote:
> When I invoke telnet with PTY.spawn, I can easily send it the
> "attention" character ^] resulting in a telnet> prompt.
> 
> When I invoke it with Open3.popen3, this doesn't work.
> 
> Can someone tell me why?
> 
> 
> Thanks,
> Hal
> 
>