How to use env variable in a tmux bind-key map?

I want my bind-key command to make use of a variable.

Here is my .tmux.conf file:

# .tmux.conf bind-key r rename-session $MY_VARIABLE 

How can I set MY_VARIABLE on a session-by-session basis?

Things I have tried that did not work:

• Run export MY_VARIABLE=my_value in bash before pressing C-b r.
• Run tmux setenv MY_VARIABLE my_value in bash before pressing C-b r.

(C-b is my prefix in tmux)

The following (based on this answer) DOES WORK:

Add a line to to .tmux.conf, like this:

# .tmux.conf MY_VARIABLE=my_value bind-key r rename-session $MY_VARIABLE 

Running C-b r the successfully renames the session. But this is less than ideal, because MY_VARIABLE=my_value is hard-coded into the .tmux.conf file; I want a way to change MY_VARIABLE on an ad-hoc basis.

1 Answer

Typically, the way round this is to go through the shell again, eg:

bind-key r run-shell 'tmux rename-session "$MY_VARIABLE"' 

The single quotes stops the variable from being expanding whilst parsing the config file. If you then later say

tmux setenv MY_VARIABLE my_value 

it will set the session environment. When you then type prefix-r the shell forked by run-shell will inherit these session variables, and the shell will be able to replace the variable by the current value for the session.