Interactive vs non-interactive terminal session question

This is a discussion on Interactive vs non-interactive terminal session question within the Tech Board forums, part of the Community Boards category; I get the "OK: " prompt when I connect to a remote forum interactively. Ie, I do something like ssh ...

  1. #1
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    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 name@arbornet.org /bin/zsh -i

    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 name@arbornet.org /bin/zsh -i

    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?

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    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.
    dwk

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  3. #3
    Captain Crash brewbuck's Avatar
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    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
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

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