til/tmux/set-session-specific-environment-variables.md

Set Session-Specific Environment Variables

tmux allows you to manage separate environments for separate projects. For me this usually boils down to arrangements of windows and tabs with different servers running.

tmux can also provide session-specific environment variables. For anything that you use environment variables for.

As an example, let's say I have one project that I always edit with VS Code. And another that uses vim.

My default editor, as configured in my ~/.zshrc file is nvim.

❯ echo $EDITOR
nvim

If I jump into the first project (one), I can set the EDITOR to code like so.

❯ tmux setenv EDITOR code

It won't apply to the current pane, but if I open a new one.

❯ echo $EDITOR
code

I can then jump to the other project (two) to set that one to vim. This time using the tmux command prompt.

<tmux-prefix>:
:setenv EDITOR vim

Again, if I open a new pane, the editor will be set.

❯ echo $EDITOR
vim

All the while, the value of EDITOR is preserved as nvim for everything outside the context of those two tmux sessions.