When logging in via ssh, automatically start a screen session if one is not running. Otherwise, display a list of available screen sessions, and automatically reconnect to the first available session after a timeout

auto-screen.sh

#! /bin/bash
# when logging in via ssh, automatically start a screen session if one is not
# running. otherwise, display a list of available screen sessions, and
# automatically reconnect to the first available session after a timeout

# Copyright (C) 2011 joh6nn@gmail.com

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

#CONFIG:
screen_opts=""
timeout="${AUTO_SCREEN_TIMEOUT:-10}"

# If not running interactively, don't do anything
[ -z "$PS1" ] && return

#check if we're in a ssh connection
if [ "$SSH_CONNECTION" ]; then
		#check if screen is currently running
		if [ -z "$STY" ]; then


		#get list of screen sessions
		screen_list=$(screen -ls | head -n -2 -)

		#check to make sure list of screen sessions isn't empty
		if [ `echo -e "$screen_list" | egrep -c "[0-9]+\.([a-zA-Z0-9\-]+)?\.[a-zA-Z]*"` -gt 0 ]; then

			#display header from session list (but not the list)
			echo -e "\n$screen_list" | head -n 2 -

			#trim footer from list of screen sessions
			screen_list=$(echo -e "$screen_list" | tail -n +2)

			#display session list with line numbers (it's a menu)
			echo -e "\n$screen_list" | awk 'NR>1 { LINE+=1; printf "\t%d%s\n",LINE,$0; }'
			echo

			# prompt, timeout a/f 10s, read only 1 char, default to most recent session
			# bash builtin read stores user input in $REPLY by default
			read -n 1 -t ${timeout} -p "Pick a # to reconnect to, or N to start new session: "

			if [[ "n" = "$REPLY" ]]; then
				#start a new session, so don't need any options
				#intentional no-op
				screen_opts=$screen_opts
			elif [ -z "$REPLY" ]; then
				#$REPLY is empty, so either we timed out or user hit enter
				#default action is to force-reconnect to the first available screen session
				screen_opts="-D -r"
			else
				#get the Nth entry from the list of screen sessions, and force-reconnect to that session
				REPLY=$(echo -e "$screen_list" | awk -v REPLY=$REPLY 'NR==REPLY { print $1}' )
				screen_opts="-D -r $REPLY"
			fi
		fi

		exec screen $screen_opts
	fi
fi