Interactive vs non-interactive terminal session question

I get the "OK: " prompt when I connect to a remote forum
interactively. Ie, I do something like
ssh [email protected] /bin/zsh -i

Quote:

---

m-net% tty
/dev/ttyp3
m-net% bbs
YAPP 3.1.1 Copyright (c)1995 Armidale Software
Registered to: Arbornet

Welcome to the
June General Conference

Fairwitness: jerryr

First item 1, last 122

Ok: quit

Now leaving June General...

---

However, I don't get the "OK: " prompt when I connect non-
interactively. Ie, I do something like
ssh -T [email protected] /bin/zsh -i

Quote:

---

m-net% tty
not a tty
m-net% bbs
YAPP 3.1.1 Copyright (c)1995 Armidale Software
Registered to: Arbornet

Welcome to the
June General Conference

Fairwitness: jerryr

First item 1, last 122
quit

Now leaving June General...
m-net%

---

The question is why doesn't the "OK: "prompt appear in the non-
interactive session?

Perhaps the "OK:" prompt is printed to standard error (stderr). I could see stderr messages appearing in a real tty but not in a pseudo one (though I'm really just guessing). Here's how you could find out.

Code:

---

$ echo This is printed to stdout
This is printed to stdout
$ echo This is printed to stderr >&2
This is printed to stderr
$

---

If the second message doesn't appear, my guess is probably right. :)

ssh tells the remote session whether the connection is interactive or not. So the other side knows, and might change its behavior accordingly.

It makes no sense to display a prompt in a non-interactive session, since there is nobody there to respond to the prompt. Don't lie about whether your session is interactive ;)