popen3 and spawn

[Hal Fulton]

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

 

[Steven Jenkins]

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?

I'd guess it's because the pipe is buffered. Try IO#flush or IO#sync.

Steve

 

[Hal Fulton]

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?

I'd guess it's because the pipe is buffered. Try IO#flush or IO#sync.

A reasonable guess, but it doesn't work for me.


Thanks,
Hal

 

[evanm]

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.