Automatically (or more easily) reconnect to a screen session after network interruption

Question

ADDED: This question is now, I believe, subsumed by this one: Using GNU Screen completely transparently and automatically

See also this related question:
https://superuser.com/questions/147873/ssh-sessions-in-xterms-freeze-for-many-minutes-whenever-they-disconnect

Original question:

It would be nice if there were a way to ssh to a machine and immediately reconnect to a specific screen session. You can do this:

laptop> ssh server.com screen -ls 

and it will show a list of screens available on server.com like so [1]:

123.pts-1 456.pts-2 

And then you might try to do this:

laptop> ssh server.com screen -dr pts-2 

but that fails, saying "Must be connected to a terminal." You have to ssh in first and then do the "screen -dr pts-2" on server.com which is no good if you have a flaky connection and get disconnected a lot. You want to be able to resume with a simple "up-arrow enter" on the laptop. (Or perhaps make it even more automatic.)

I have a rihackulous solution to this problem which I'll post as an answer and hope it gets downvoted to oblivion in favor of the Right Way to deal with this.

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Footnotes:

[1] Or, better, if you created the screen sessions with names like "screen -S foo" and "screen -S bar" then you'll get a friendlier list like:

123.foo 456.bar 

and can reconnect with, eg, "screen -dr foo".

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Mini screen tutorial, incorporating the answer to this question:

Login in to server.com and do

screen -S foo  

and then never log out of that session again. To reconnect to it from elsewhere, do

ssh -t server.com screen -dr foo 

To list available screens to reconect to:

screen -ls 

or, of course,

ssh server.com screen -ls 

to check on server.com's available screens remotely.

I now use the following alias (tcsh), based on Jason's answer below, to connect to a named screen if it exists or create and connect otherwise:

alias ssc 'ssh -t \!:1 "screen -S \!:2 -dr || screen -S \!:2"' 

Answer 1

Does the -t option do what you want?

      -t      Force pseudo-tty allocation.  This can be used to execute arbi-              trary screen-based programs on a remote machine, which can be              very useful, e.g. when implementing menu services.  Multiple -t              options force tty allocation, even if ssh has no local tty. 

So:

laptop> ssh -t server.com screen -dr pts-2 

This seems to work in my installation.

Answer 2

This is now subsumed by this: Using GNU Screen completely transparently and automatically

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Here's a script, ssc, that works just like ssh but takes a third argument to specify the screen to reconnect to, or the name of a new screen. I believe this script subsumes everything in the original question.

#!/usr/bin/env perl # Use 'ssc' (this script) instead of 'ssh' to log into a remote machine. # Without a 3rd argument it will list available screens. # Give it a 3rd argument to attach to an existing screen or specify a new #   screen.  Eg, ssc remote.com foo # The numbers in front of the screen tag can usually be ignored. # Screen is a little too clever though in that if there's an existing screen "bar" #   and you say "ssc remote.com b" it will reconnect you to "bar" instead of making #   a new screen "b".  It's like invisible and silent tab-completion.  if(scalar(@ARGV)==0 || scalar(@ARGV) > 2) {   print "USAGE: ssc remote.com [screen name]\n"; } elsif (scalar(@ARGV) == 1) {   $machine = shift;   @screens = split("\n", `ssh $machine screen -ls`);   for(@screens) {     if(/^\s*(\d+)\.(\S+)\s+\(([^\)]*)\)/) {       ($num, $tag, $status) = ($1, $2, $3);       if($status =~ /attached/i) { $att{"$num.$tag"} = 1; }       elsif($status =~ /detached/i) { $att{"$num.$tag"} = 0; }       else { print "Couldn't parse this: $_\n"; }     }   }   print "ATTACHED screens:\n";   for(keys(%att)) { print "  $_\n" if $att{$_}; }   print "DETACHED screens:\n";   for(keys(%att)) { print "  $_\n" unless $att{$_}; } } else {   $machine = shift;   $tag = shift;   system("ssh -t $machine \"screen -S $tag -dr || screen -S $tag\""); }