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

auto-tmux.sh

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

# Copyright (C) 2017 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:
tmux_opts=""
timeout="${AUTO_TMUX_TIMEOUT:-10}"

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

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

		#get list of tmux sessions
		tmux_list=$(tmux ls)

		#check to make sure list of tmux sessions isn't empty
		if [ -n ${tmux_list} ]; then

			#display session list (it's a menu)
			echo -e "\n$tmux_list"
			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 attach to, or N to start new session: "

			if [[ "n" = "$REPLY" ]]; then
				#start a new session, so don't need any options
				#intentional no-op
				tmux_opts=$tmux_opts
			elif [ -z "$REPLY" ]; then
				#$REPLY is empty, so either we timed out or user hit enter
				#default action is to attach to the first available tmux session
				tmux_opts="attach"
			else
				#attach to the entry that the user selected
				tmux_opts="attach -t $REPLY"
			fi
		fi

		exec tmux $tmux_opts
	fi
fi