Persistent SSH

Recently I’ve had issues with dropping network connections or wanting to connect and keep working on the same thing from other systems. Most of you probably already know the answer (screen/tmux). This sounds easy enuogh, but it’s not very automated.

I don’t want to SSH into the system AND start screen AND detach AND reattach. That’s just asking way too much of someone like me.

Here’s the very simple solution. In my ~/.bashrc file I appended this section of code.

ssh() {command ssh "$1" -Xt screen -aAdr -RR work bash}

This makes a function called SSH. Bash always uses a function over a command if the two collide. So running ssh will call this function instead of calling the command(app) /usr/bin/ssh. If you want to not use the function

but use SSH you have two options. The first option is call the function something else. Either s(), sshw(), or something_else().

Recursion can happen. The “command” command is a BASH built-in function if I recall correctly. This command breaks the function calls so it will call /usr/bin/ssh (found from $PATH) rather than ssh(). Simple enough to understand but not so easy to explain. I hope I did OK with that.

The next part of this is the $1. This is the first parameter passed to the ssh command. Example being “ssh foo.com” will insert foo.com in place of $1.

The rest of this is pretty simple. You establish the SSH connection and call screen. If screen is running an instance named work it will attach to that and boot the other connection. If the instance isn’t named doesn’t exist

then it gets created. Then “bash” following is just the command executed on the new instance. I have a similar command that has irssi at the end.

While writing this I was thinking about the need for using ssh to connect to another server. Maybe you want to do something entirely different. The answer is pretty simple. The function is designed so you only pass one

parameter to it. So any additional parameters means you’re doing something different.

To make it simple I just came up with this function instead:

ssh() {
    if [[ "$2" == "" ]]; then
        command ssh "$1" -Xt screen -aAdr -RR work bash
    else
        command ssh $@
    fi
}

If you only pass the server you’re connecting to into the ssh command, it will work with screen. If you pass it with more than one parameter it just runs /usr/bin/ssh with the parameters you used.

This is a simple and effective way to always be using screen/tmux so that connection hiccups are never more than a simple reconnect.