A Tmux Crash Course

I’ve been using Tmux for about six months now and it has become just as essential to my workflow as vim. Pane and window management, copy-mode for navigating output, and session management make it a no-brainer for those who live in the terminal (and especially vim). I’ve compiled a list of tmux commands I use daily to help me work more efficiently.

If a tmux command I mention is bound to a keyboard shortcut by default, I’ll note that in parenthesis.

Session Management

Sessions are useful for completely separating work environments. I have a ‘Work’ session and a ‘Play’ session; in ‘Work’, I keep everything open that I need during my day-to-day development, while in ‘Play’, I keep open current open-source gems or other work I hack on at home.

tmux new -s session_name

creates a new tmux session named session_name

tmux attach -t session_name

attaches to an existing tmux session named session_name

tmux switch -t session_name

switches to an existing session named session_name

tmux list-sessions

lists existing tmux sessions

tmux detach (prefix + d)

detach the currently attached session

Windows

Tmux has a tabbed interface, but it calls its tabs “Windows”. To stay organized, I rename all the windows I use; if I’m hacking on a gem, I’ll name the window that gem’s name. The same thing goes for client applications. That way, I can recognize windows by context and not what application it’s running.

tmux new-window (prefix + c)

create a new window

tmux select-window -t :0-9 (prefix + 0-9)

move to the window based on index

tmux rename-window (prefix + ,)

rename the current window

Panes

Panes take my development time from bland to awesome. They’re the reason I was able to uninstall MacVim and develop solely in iTerm2. I don’t have to switch applications to switch contexts (editing, reading logs, IRB, etc.) - everything I do, I do in a terminal now. People argue that OS X’s Cmd+Tab is just as fast, but I don’t think so.

tmux split-window (prefix + ")

splits the window into two vertical panes

tmux split-window -h (prefix + %)

splits the window into two horizontal panes

tmux swap-pane -[UDLR] (prefix + { or })

swaps pane with another in the specified direction

tmux select-pane -[UDLR]

selects the next pane in the specified direction

tmux select-pane -t :.+

selects the next pane in numerical order

Helpful Tmux commands

tmux list-keys

lists out every bound key and the tmux command it runs

tmux list-commands

lists out every tmux command and its arguments

tmux info

lists out every session, window, pane, its pid, etc.

tmux source-file ~/.tmux.conf

reloads the current tmux configuration (based on a default tmux config)

Must-haves

These are some of my must-haves in my tmux config:

# remap prefix to Control + a
set -g prefix C-a
unbind C-b
bind C-a send-prefix

# force a reload of the config file
unbind r
bind r source-file ~/.tmux.conf

# quick pane cycling
unbind ^A
bind ^A select-pane -t :.+

Workflow

During the day, I’ll work on one or two Rails apps, work on my dotfiles, run irssi, and maybe run vim in another window to take notes for myself. As I mentioned, I run all of this inside one tmux session (named work) and switch between the different windows throughout the day.

When I’m working on any Ruby work specifically, I’ll have a 75%/25% vertical split for vim and a terminal so I can run tests, interact with git, and code. If I run tests or ‘git diff’ and want to see more output than the 25% allots me, I’ll use tmux to swap the panes and then move into copy mode to see whatever I need to see.

Finally, I run iTerm2 in full-screen mode. Switching between OS X apps for an editor and a terminal is for chumps!

Love, hate, & tmux

Many at thoughtbot run their editor+shell combos inside of tmux. Some remote pair program with ssh, vim, and tmux.

Getting started with tmux, these are the questions I’ve had.

How do I get started?

Install tmux, read the documentation, and fire it up.

brew install tmux
man tmux
tmux -u

Can I make the environment look good?

Yes. We have these lines in tmux.conf in thoughtbot/dotfiles:

# improve colors
set -g default-terminal "screen-256color"

# soften status bar color from harsh green to light gray
set -g status-bg '#666666'
set -g status-fg '#aaaaaa'

# remove administrative debris (session name, hostname, time) in status bar
set -g status-left ''
set -g status-right ''

What’s a prefix?

The “prefix” namespaces tmux commands. By default it is Ctrl+b. In our tmux.conf in thoughtbot/dotfiles, we bound it to Ctrl+a:

# act like GNU screen
unbind C-b
set -g prefix C-a

How can I scroll up to see my backtraces?

This was non-obvious to me.

Enter “copy mode”:

prefix+[

Use vim bindings to page up and down:

Ctrl+b
Ctrl+f

How can I copy text?

Add this to your tmux.conf:

# enable copy-paste http://goo.gl/DN82E
# enable RubyMotion http://goo.gl/WDlCy
set -g default-command "reattach-to-user-namespace -l zsh"

How can I make tmux act more like vim?

Add this to your tmux.conf to use vim’s home-row keys for movement between windows and panes:

# act like vim
setw -g mode-keys vi
bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R
bind-key -r C-h select-window -t :-
bind-key -r C-l select-window -t :+

How do I name sessions?

One day I might work on Airbrake. Another day, a client project. I’d like to name my tmux sessions so I can leave one, drop into another, and go back to the original with all my state maintained (files still open in my editor, console/logs I want open, etc.).

Create a new session:

tmux new -s airbrake

Attach to a session:

tmux attach -t airbrake

How do I split and move between windows?

Create a window:

prefix c

Move to window 1:

prefix 1

Move to window 2:

prefix 2

Kill a window:

prefix x

I believe in setting my mouse free but it takes time for muscle memory to make this fast.

How do I reload ~/.tmux.conf?

After editing ~/.tmux.conf, execute this from a shell:

tmux source-file ~/.tmux.conf

Give it a shot

I’ve had a love-hate relationship with tmux in my first week using it, but the brief moments of flow I’ve experienced so far are enough to keep trying it.

Give tmux a shot and if you have any other tips, I’d love to hear them.

Written by Dan Croak.