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SteveNuts

Pressing enter then ~. will gracefully shutdown hung ssh sessions

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More generally, type ~ as an escape sequence.

For example, type ~^Z to put a session in the background.

Similarly, type ~~ to send an escape sequence in an inner session, etc...

...

  There's a program called SSH to get to another CPU.
  Tilde is the escape, it's doubled to send it through,
  And "quit" is tilde-.

I think you know how the rest goes...

What does this reference?

I am not sure, but it looks vaguely familiar. There is a text-based game called adventure game called Dunnet where you come across a CPU card, and do some stuff with it later on. As far as I remember, the game predates SSH, so the game either had Telnet or FTP. My memory fades.

It references "The TELNET Song" by Guy L. Steele (a.k.a The Great Quux). The original is about Telnet, and given the subject of discussion, the reference seemed a natural one to make.

I don't - and in fact I finally got around to creating a HN account in order to ask you. Googling that just leads me back to this discussion. What's it from?

It's parodying "the TELNET song," by Guy L. Steele.

For more information: http://wonderingminstrels.blogspot.com/2004/01/telnet-song-g...

If you have an ACM subscription, the sheet music was published in Communications of the ACM (Volume 27, Issue 4; April 1984): http://dl.acm.org/citation.cfm?id=1035691

Or type ~? for a list of escapes.

I am amazed by the fact that I never accidentally trigger this feature.

Hah, yeah I seem to remember Ctrl-S leaving me flustered for quite a while when I first stumbled on it!

^-Q is your friend!

Yes, it's a good choice of characters.

Specifically, the escape sequence is "\n~", with various options (visible by typing "\n~?"), and if the option is unknown it passes the "\n~{x}" as-is.

The biggest false positive you'll see is "\n~v", when executing bins out of the home dir of a user starting with the letter 'v'.

You'd probably trigger it more often if ~/ didn't conveniently map to ~/ - it's quite cleverly designed in a way. Indeed, most of the two-character combinations you're likely to type starting with ~ map to themselves.

It's annoying when you're adminning users and atually want to type "~user/foo" though.

Sadly it will shutdown only the 'outer' ssh session, so if you ssh to foo, and then from foo ssh to bar, and type ~. then the client->foo session is shut down but the foo->bar session is still around.

You need to type one ~ per session level toy want to reach and terminate. In your example, type ~~. to terminate the inner session, leaving the outer one live.

To kill the inner one you need to escape it: ~~. ~? displays the supported escape sequences.

nice one, never seen that - always used ^D/exit

Those are yet more graceful -- for when the shell is responsive. Use ~. in cases where for some reason you cannot get access to the terminal anymore but remote sshd is responsive.

iirc, enter-~-. isn't anything to do with the remote sshd. Instead, it escapes to the local ssh client (enter-~) that it should close (.). Which is really useful for if the remote sshd blew up, or, more commonly, your connection was broken.

~. (and the other ~ commands) are handled locally, not by the remote sshd. I use it when my network cuts out or something and my ssh session is unrecoverably stuck

Actually the remote sshd does not need to be responsive, because "<cr>~." is interpreted by the local ssh client. Very convenient if the TCP connection is stuck.

You can also type "<cr>~?" for a list of other commands supported by the local ssh client. Among other things, "<cr>~C" opens a command line interpreter on the client side of the ssh client, allowing you to add and remove TCP port forwarding without restarting the connection.

Ahg, I wish it let you scp files into your working directory too. That's be convenient.

Long ago I sent a patch for uploading downloading using this escape sequence, using zmodem like how an old windows SSH client (I forget the name) used to allow uploading/downloading files.

You log in, type "rz<enter>", and then use escape sequence to upload a file. (similar for downloading)

The patch was rejected. Shame. It's very useful when hopping 6 steps to upload a file.[1]

I can't find the patch now, but I'm considering rewriting it as a an `expect` script. My `expect` scripts tend to have trouble with SIGWINCH propagation though, so not optimal. Also you have to remember to wrap with the `expect` script at (and preferably only at) the one "jump" you want to send from/to with the final destination.

[1] No, nothing illegal. Just that some networks mandate SSH jumpgates, and sometimes multi-level.

You can also layer the number of ~'s to skip over intermediary SSH sessions and send the escape to the proper one.

\n~~. will escape the 2nd box you've SSH'd to, not the one it was originated from.

Useful for escaping a screen'd SSH session that you might access through a jumphost.

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