Happy tmux

I was recently introduced to the joys of tmux by a colleague, and felt like sharing a bit of what I learned.

What’s tmux?

tmux is a terminal multiplexer, which is a fancy way of saying that tmux manages multiple terminals for you – and it does a couple things for you, very well.

• It provides a ‘window manager’ for terminals – you can view multiple terminals at the same time, with many options for tiling (e.g. vertical and horizontal splits, 4-pane layouts, and so on)

• Persistent sessions, so you can start a session at some time and re-attach to it at a later time. Incredibly useful when working remotely, e.g. when running code on a cluster, or otherwise ‘remote’ device.

How do I install it?

If you’re on a *nix distribution, you can get tmux using your package manager; if you’re on OS X, I suggest using homebrew and performing a simple brew install tmux.

How do I use it?

You can launch tmux just by calling tmux from your shell. After running that, you should see a new shell, but with tmux’s status bar at the bottom. Like vim, tmux provides a lot of modal functionality with a minimal amount of visual feedback; ie, it assumes you know what you’re doing.

When working with tmux, it’s mostly like working in any old plain terminal session – ie, after starting tmux, you’ll just be planted into a shell and you can do things as you normally would. The only difference is the little status bar at the bottom:

However, by typing a special prefix key, you can switch to what I’ll call tmux-mode and start asking tmux to execute some commands.

By default, the prefix key combination is Ctrl + B. If you’re following along, try executing these commands to create a tmux session and then split your ‘window’:

tmux
<Ctrl + B> %

After doing this, you should see you now have two terminals open, in a vertical split. Sweet!

You can then switch back-and-forth between these two terminals with e.g.

<Ctrl + B> <Right>  ## select right pane
<Ctrl + B> <Left>   ## select left pane

What you’re seeing now is, in tmux parlance, is two panes in a single window. This is a bit at odds with how we normally call these; e.g. I would prefer to say we have two windows open with a single tab, but it is what it is.

Let’s try creating a new window (tab) and navigating back and forth:

<Ctrl + B> c ## 'c' for create
<Ctrl + B> n ## 'n' for next
<Ctrl + B> p ## 'p' for previous

You can also list the set of all available windows with <Ctrl + B> w – this gives you a list of all available windows and select one from there.

Now, we have a good ‘sense’ for how tmux works:

1. Type the prefix key,
2. Press a second key to perform from tmux action.

There’s a lot of utility in having an editor open in one pane, documentation in another, and perhaps an active console in another.

There’s plenty more to learn as far as tmux keybindings and functionality goes, but I’ll leave most of that to your Google-fu, as well as some links that I found particularly helpful:

• Practical tmux
• Tools I use: tmux

And, if you’re on OS X, follow this link to get tmux to use the system clipboard.

What’s in my .tmux.conf?

tmux is similar to Emacs in that you’re generally encouraged to configure it to your own taste.

Alternatives: GNU screen

You might be familiar with screen: tmux is a (newer) alternative with a much saner configuration language, but there are still many who swear by screen. In my (uneducated) opinion, unless you’re already very comfortable with screen, you’re better off learning and using tmux. If you’re curious, there was a lively debate on Hacker News.