Create new tmux session from inside a tmux session

Question

I\'m writing a shell script that creates / attaches or switches to a given session, depending on whether one is inside tmux and the session exists.

I\'ve got everything

Answer 1

How to create the script

This script will check if a session exists. If session does not exist create new session and attach to it. If session does exist nothing happens and we attach to that session. Feel free to replace `~/development' with project name.

$ touch ~/development && chmod +x ~/development

# ~/development

tmux has-session -t development
if [ $? != 0 ]
then
  tmux new-session -s development
fi
tmux attach -t development  

New session from terminal

Let's create two detached sessions, list them, attach to one and then from within tmux cycle through sessions.

tmux new -s name -d works from inside tmux because we're creating a new detached session. Otherwise you'll get a nesting error.

$ tmux new -s development -d
$ tmux new -s foo -d
$ tmux ls
> development: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54]
> foo: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54]
$ tmux attach -t
$ tmux ls
> development: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54] (attached)
> foo: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54]

New session from within tmux

We are now inside or better known as attached to our target session. If we try to create a new session while attached it will result in a nesting error.

$ tmux new -s bar
> sessions should be nested with care, unset $TMUX to force

To solve this we create a new detached session. e.g.,

$ tmux new -s bar -d
$ tmux ls
> development: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54] (attached)
> foo: 1 windows (created Wed Jan 13 11:31:38 2016) [204x54]
> bar: 1 windows (created Wed Jan 13 17:19:35 2016) [204x54]

Cycle (switch) Sessions

• Prefix ( previous session
• Prefix ) next session

note: Prefix is Ctrl-bby default. You can bind Prefix to Ctrl-a and in Mac OSX you can change Caps Lock to ctrl system preferences > keyboard > modifier keys

Attach to a session using command mode while inside tmux

Trying to attach to a session without detaching will result in an error.

$ tmux attach -t development
> sessions should be nested with care, unset $TMUX to force

Instead use command mode Prefix : then type attach -t session_name and hit enter.