The main way in which options are set and configured within tmux is through the appropriately named set-option command.

This command can be called on its own to set an option temporarily. However, most of the time, we will use it to set options within a tmux configuration file so each time we launch tmux, the options are set the way we would like.

For a taste of using the set-option command to set an option temporarily, open a terminal window and launch tmux; alternatively, if you've been following along through Chapter 1, Jump Right In, just type the following command in the window:

$ tmux set-option status off

Once you do this, the status bar will disappear! This setting is only temporary, so if you leave it as is, end the session, and restart tmux or create a new session, it will not load this setting. In other words, a status bar will appear.

What you have done is that you've told tmux to set the option status to a value of off. You can use this command to set...

In order to keep the settings around after restarting tmux, we will create a configuration file that will include all the information about what options we want to set and to what values.

Like many other Unix-based utilities, configuring tmux is as simple as creating a file with the name .tmux.conf in your home directory.

However, unlike many other configuration files, a tmux configuration file does not contain some kind of specific configuration language for the program, rather it consists of a series of tmux commands that are run, in order, when tmux starts up. Most of the commands we'll see are simple set-option commands similar to the commands we played with in the previous examples. Let's create and start building our configuration file:

$ cd ~
$ touch .tmux.conf

Open this newly created file in your favorite text editor and we're ready to rock!

As we discovered in Chapter 1, Jump Right In, tmux tries to help developers by providing two sets of key bindings, one each for the two most widespread text editors. If you swing one way or the other, this is likely to be one of the first things you'll want to change to make tmux feel right for you.

The default for tmux is to use the Emacs mode keys, so if you are an Emacs user, you may be all set. tmux also tries to help out and might, based on environment variables, switch to one group or the other by default. To check which mode tmux is currently in, run the following command:

$ tmux show-options -g | grep key

You should get an output that looks something similar to the following command:

$ status-keys emacs

If you are in the mode you'd like to be in, you can do nothing. If you are in the wrong mode though, you would most likely want to add the following couple of lines to your .tmux.conf file, obviously choosing the appropriate editor:

set-option -g status-keys emacs
set...

First, it's worthwhile to note that one of the main benefits of tmux is to obviate the need to reach for your mouse as often as you otherwise would. So, some purists would balk at the notion of enabling mouse modes for tmux.

That said, it is often rather convenient to use the mouse to scroll, select text, resize panes, choose an option from a list, and more. And yes, tmux allows you to do all of that with the mouse. These features are disabled by default so to enable them, we need to add the following lines to our .tmux.conf (either Emacs or vi):

set-window-option -g mouse-mode on
set-option -g mouse-select-window on
set-option -g mouse-select-pane on
set-option -g mouse-resize-pane on

This will enable mouse functionality in all of the ways we described. We haven't yet dealt with panes, but when we touch on that in Chapter 3, Sessions, Windows, and Panes, it will be more apparent how using the mouse to resize them will be incredibly convenient.

We learned a bit about the status bar in the last chapter when we discussed changing the session and window names. This status bar is highly customizable, and it's a great place to start learning about configuring tmux. We can change the status bar colors, what appears on the status bar, the alignment, and much more.

Binding keys will allow you to change the keys and key combinations that tmux will recognize for any command. This also allows us to create new key combinations for existing commands or change the key binding for any existing keys used by tmux. It even lets you assign new key bindings to any command we can dream about.

The commands to which we can bind keys can even prompt for user input. There is no constraint on uniqueness, so we could bind multiple keys to issue the same command or bind no keys for a particular command.

What this all means is that while there is not an existing key combination available to reload the tmux source file, we can make up our own key combination and assign it to the rather lengthy source-file command so we don't have to type the whole thing each time we want to reload the configuration.

First, let's find a good key combination to bind for this command.

Now let's say there is a key binding that you want to remove for some reason. This is very easy; just add an unbind directive to your .tmux.conf file.

Say we wanted to unbind 0 from its default action of selecting window 0 for some reason. To do this, simply add the following code snippet to your configuration:

unbind 0

Note that there is no need to explicitly unbind a key before binding it to something else; every key can only have one binding. So, we find it rather rare to use this bit of utility, but it's nice to know it's there when you need it.

Last time we touched the status bar, we altered its colors, but we did not do anything to change its content. tmux allows us to change a lot of different aspects of the content of the status bar. We won't have an in-depth look at every possible configuration, but will explain the concept and show one example.

So, the status bar has three chunks basically:

Recall our status bar, which appears as shown in the following screenshot:

By default, status-left shows the name of the current session in brackets. We named our session tutorial, so status-left for us is [tutorial].

We can change these. They are just simple strings with some magic character pairs that tmux fills in based on what they mean. For...

Thus far, all of the options we have set had the -g flag. This means that the option applies globally. However, there are three types of options: server options, session options, and window options.

There are also multiple flags that indicate how a given option should affect or be affected. This sounds complex, but it's rather simple.

A server option will apply to any client that connects to tmux. Under the hood, when you type and run the tmux command the first time, tmux creates a server; then, it creates your client and connects to the server it started. This is the magic that allows you to detach your session, reattach it later, and have everything running as you left it because the tmux server keeps chugging in the background. So an option specified with the -s flag will apply to the server, meaning it will affect any clients that attach to it.

A session option will apply to the current session. This means that two clients could connect to the same server and each could have...