Create a session in the background if it doesn't exist but do not attach in tmux

Question

I've looked at this similar question which asks about creating a tmux session, or attaching if it doesn't exist.

What I'd like to do is a little different: create a tmux session if it doesn't exist, but don't attach. The plan is to create a few different sessions with canonical names, then send commands to them using tmux send. Is there an easy way in tmux or shell scripting to create a session with a specific name only if it doesn't exist?

Answer 1

If you try to create a session with the same name tmux returns an error with exit code 1.

drizzt@liara ~ % tmux new-session -d -s test 
drizzt@liara ~ % tmux new-session -d -s test
duplicate session: test
drizzt@liara ~ % echo $?
1
drizzt@liara ~ % 

If you don't like the duplicate session error you can do something like:

drizzt@liara ~ % tmux has-session -t test || tmux new-session -d -s test