tmux/setw

About tmux setw
setw is only meaningful inside a tmux context.
But there are two different ways it can be valid, depending on how you run it.
1. setw is a tmux command, not a shell command
setw is short for:
- ```
set-window-option
```
  It is part of tmux's command language, not your shell's.
  So this:
- ```
setw -g pane-border-style fg=colour238
```
  is not valid in bash, zsh, etc.
  If you type it in a normal terminal that is not inside tmux, you'll get:
- ```
command not found
```
  because your shell has no idea what setw is.
2. When it is valid
- ✅ Inside a tmux session, in command mode
  If you're inside tmux:
  - Press:
    - prefix + :
  - Type:
    - setw -g pane-border-style fg=colour238
  - Hit Enter
    That runs the command in tmux's command interpreter.
- ✅ Outside tmux, if you prefix with tmux
  You can also run it from a normal shell like this:
  - tmux setw -g pane-border-style fg=colour238
    In this form:
  - tmux = client program
  - setw = subcommand passed to the tmux server
    tmux sends it to the running server and executes it.
3. Where it is not valid
- ❌ Plain shell (unqualified)
  This will never work:
  - setw -g pane-border-style ...
    unless:
  - you're inside prefix + : command mode in tmux.
4. Rule of thumb
- Inside tmux command mode: ✅ setw ...
- Normal shell: ✅ tmux setw ...
- Normal shell without tmux: ❌ setw ...
- Inside tmux pane as shell command: ❌ unless prefixed

5. Mental model

Think of tmux like git:

git commit     # works
commit         # doesn't

Same pattern:

6. Practical advice
If you're experimenting:
- Inside tmux live: → prefix : then type setw ...
- Writing config or scripts: → use tmux setw ...