Script for re-attaching to existing tmux sessions while maintaining window independence, à la `screen -x`

tmux-attach.bash

#!/bin/bash

#
# Re-modified script from
#     https://mutelight.org/practical-tmux
# Which is modified from:
#     http://forums.gentoo.org/viewtopic-t-836006-start-0.html
#
# chmod +x it and put it in your $PATH for easy use; I stuck it in
# ~/.tmux-attach.bash and added an alias for it, do whatever you like.
#

# Works because bash automatically trims by assigning to variables and by
# passing arguments
trim() { echo $1; }

if [[ -z "$1" ]]; then
    echo "Specify session name as the first argument"
    exit
fi

# Only because I often issue `ls` to this script by accident
if [[ "$1" == "ls" ]]; then
    tmux ls
    exit
fi

base_session="$1"
# This actually works without the trim() on all systems except OSX
tmux_nb=$(trim `tmux ls | grep "^$base_session" | wc -l`)
if [[ "$tmux_nb" == "0" ]]; then
    echo "Launching tmux base session $base_session ..."
    tmux new-session -s $base_session
else
    # Make sure we are not already in a tmux session
    if [[ -z "$TMUX" ]]; then
        # Kill defunct sessions first
        old_sessions=$(tmux ls 2>/dev/null | egrep "^[0-9]{14}.*[0-9]+\)$" | cut -f 1 -d:)
        for old_session_id in $old_sessions; do
            tmux kill-session -t $old_session_id
        done

        session_num=$(tmux ls | grep "^$base_session-" | cut -d- -f2 | sort -rn | head -n1)

        if [[ -z "$session_num" ]]; then
            session_num=0
        fi

        session_num=$(($session_num + 1))

        echo "Launching copy of base session $base_session ..."
        # Session is is date and time to prevent conflict
        session_id=$base_session-$session_num
        # Create a new session (without attaching it) and link to base session
        # to share windows
        tmux new-session -d -t $base_session -s $session_id
        # Create a new window in that session
        #tmux new-window
        # Attach to the new session
        tmux attach-session -t $session_id
        # When we detach from it, kill the session
        tmux kill-session -t $session_id
    fi
fi