Add Set Session-Specific Environment Variables as a tmux til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1175 TILs and counting..._
+_1176 TILs and counting..._
 
 ---
 
@@ -1061,6 +1061,7 @@ _1175 TILs and counting..._
 - [Remove The Delay On The Escape Key](tmux/remove-the-delay-on-the-escape-key.md)
 - [Rename The Current Session](tmux/rename-the-current-session.md)
 - [Reset An Option Back To Its Default Value](tmux/reset-an-option-back-to-its-default-value.md)
+- [Set Session Specific Environment Variables](tmux/set-session-specific-environment-variables.md)
 - [Show The Current Value For An Option](tmux/show-the-current-value-for-an-option.md)
 - [Swap Split Panes](tmux/swap-split-panes.md)
 - [Switch To A Specific Session And Window](tmux/switch-to-a-specific-session-and-window.md)

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

@@ -0,0 +1,51 @@
+# 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`.
+
+```bash
+❯ echo $EDITOR
+nvim
+```
+
+If I jump into the first project (`one`), I can set the `EDITOR` to `code` like
+so.
+
+```bash
+❯ 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.
+
+
+```bash
+<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.