11/24/2024 Tmux basics

tmux is a terminal multiplexer.

A practical example

Simply run tmux in your shell : you will enter a session.

Note that, you can still interact with the shell just like before.

So now we can experiment something to illustrate what it feels being in a session :

Let's run a dummy long-running program, like this :

sh -c 'while true; do echo "This is a long-running program"; date ; sleep 5; done'

Let the long program run, but let's find a way to quit our terminal.

I suppose you can for example go and find your terminal icon, and right-click quit on it.

Then, let's open a fresh new instance of our terminal, and run this command :

tmux attach

We are back in the session, and we can see that our long-running program did run continuously during our absence, without any interruption.

Basic concept

When you enter a tmux session, you get a shell that is not bound to your current terminal instance.

Some interesting consequences :

• you can quit your terminal instance without interrupting the session
• you can join the session from another terminal instance with tmux attach
• you can work in the same session on multiple terminal instances.

A common and useful case :

Let's say you are about to run a critical process on a remote machine you're connected with via ssh.

You should ensure that, if your network connection causes the ssh connection to fail, your critical process keeps running safely on the remote machine.

For that, use tmux on the remote machine, and run your critical program inside a session.

Then if, by accident, you get disconnected from the remote machine, you will sooner or later be able to ssh again into it. And by running tmux attach, you'll see that your critical program kept running safely.

Learn to configure tmux rather than the terminal.

You may have seen that tmux comes with a default bar sitting at the bottom of the terminal.

In fact, tmux can offer more than just terminal multiplexing :

• you can create multiple sessions, and switch between them.
• you can open multiple windows in a session
• you can open multiple panes in a window
• you can fully customize the look of a session ( status-bar, window-bar, etc )

By learning a bit of tmux configuration, we get the opportunity to :

• use a lightweight terminal like alacritty and delegate to tmux all the multi-window stuff.
• setup key-bindings, tools, plugins, a lot that a terminal alone cannot provide.

See documentation : Man tmux

Basic commands and key-bindings

tmux ls
tmux attach
tmux detach
tmux kill-session

Pro tip :
on macOS,
go to settings > Keyboard > Modifier Keys,
and remap CapsLock to Ctrl

On the keyboard, Ctrl-B is the default prefix to send commands to tmux.

Ctrl-b + c : create a new window in the session
Ctrl-b + p : go to previous window
Ctrl-b + n : go to next window

In case you want to change this default prefix to e.g Ctrl-A,
create a file named $HOME/.tmux.conf with the following content :

unbind C-b
set-option -g prefix C-a
bind C-a send-prefix

then apply this new configuration :

tmux source ~/.tmux.conf

A simple configuration

TO DO ;)