I haven’t been using tmux since I’m a happy user of iTerm2. Eventhough tmux had been used in servers I used to work with, I preferred avoiding it because of the fallacious assumption that it would be hard to remember all those scary key-shortcuts. I gave it a try today, and totally regret for not learning it earlier.

  1. Why tmux
  2. Installation
  3. Usage
  4. Managing Sessions
  5. Configuration file
tmux window

Why tmux?

tmux is a terminal multiplexer. It enables to run multiple processes in one terminal.

With tmux you can create multiple sessions in a terminal, each session can have multiple windows which can be split into panes. Sessions can be attached/detached to the working terminal. This is heavily useful for multiuser concurrent system-terminals.

Another advantage is that processes running inside tmux sessions can continue even after closing the terminal.


In OSX, tmux can be installed with homebrew.

$ brew install tmux


Typing tmux will start a new session, you can see the session status displayed on the bottom bottom of the window in a green bar.

$ tmux

When you are inside tmux session, every tmux command need to have a prefix. By default it is CTRL+B. For example, commands below does splitting window into vertical panes.


Here is a list of useful commands,

Prefix Command Use
 CTRL+B  Sessions
s list sessions
:new<ENTER> create new session
$ rename session
d detach session
w list windows
f find window
c create window
& kill window
, rename window
n next window
p previous window
% vertical split
" horizontal split
q show pane numbers, if pane number is typed immediately, control is switched to that pane
x kill pane
z toggle zoom pane
<ARROW KEY> switch to pane pointed by arrow key
o swap panes
{ move current pane to left
} move current pane to right
<SPACE BAR> toggle between different pane layouts
t show time
? list shortcuts
: prompt

As mentioned in the last entry of table above, CTRL+B : will give tmux prompt at the bottom of the window, you can enter commands there.

: <command>
Command Use
:setw synchronize-panes synchronize cursor on all panes (repeat same for toggle)
:resize-pane -L resize current pane to left
(Available flags: L, R, T, D for left, right, top, down respectively)
-D 50 resize current pane down by 50 cells
-t 2 -R 30 resize pane number 2 right by 30 cells

Managing sessions

Sessions are by default numbered as 0, 1, 2, .. You can name/rename sessions with strings.

Action Command
create session $ tmux
$ tmux new
$ tmux new -s <session_name>
list sessions $ tmux ls
detach session CTRL+B d
attach session $ tmux a -t <session_name>
kill session $ tmux kill-session -t <session_name>

Configuration file

If you want to save commands entered in tmux prompt to for all of your sessions, it can be saved to configuration file ~/.tmux.conf

Here is an example config file:

# enable mouse actions
set -g mouse on

# change default PREFIX from CTRL+B to CTRL+A
unbind C-b
set -g prefix C-a
bind C-a send-prefix

# split panes using | and -
bind | split-window -h
bind - split-window -v
unbind '"'
unbind %

# reload config file inside session with PREFIX+r
bind r source-file ~/.tmux.conf

# Change theme of pane border
set -g pane-border-fg red
set -g pane-active-border-fg yellow

For more options: man tmux