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Status bar and styling {#status-bar}

The status bar, or status line, serves as a customizable taskbar in the bottom of tmux. It is comprised of 3 sections. The status fields on either side of the status line are customizable. The center field is a list of windows.

The status-left and status-right option can be configured with variables.

It's configurable through the .tmux.conf file and modifiable live through using $ tmux set-option.

I> Finding your current status line settings I> I> {language=shell, line-numbers=off} I> $ tmux show-options -g | grep status

Window status symbols

This window list is between the left and right status bar regions.

tmux indicates status of a window through symbols. See below:

Symbol Meaning
* Denotes the current window.
- Marks the last window (previously selected).
# Window is monitored and activity has been detected.
! A bell has occurred in the window.
~ The window has been silent for the monitor-silence interval.
M The window contains the marked pane.
Z The window's active pane is zoomed.

Reminder: A pane can be zoomed via Prefix + z. To unzoom, press Prefix + z or move left / right / up / down panes.

Date and time

status-left and status-right accept variables for the date.

This happens via piping the status templates through format_expand_time in format.c, which routes right into strftime(3) from time.h.

A full list of variables can be found in the documentation for strftime(3). This can be viewed through $ man strftime on Unix-like systems.

Shell command output

You can also call applications, such as tmux-mem-cpu-load, conky, and powerline.

For this example, we'll use tmux-mem-cpu-load. This works on Unix-like systems like FreeBSD, Linux distributions, and macOS.

To build from source, you must have CMake and git, which are available through your package manager. You must have a C++ compiler. On macOS, install Xcode CLI Utilities. You can do this by going to Applications -> Utilities, launching and typing $ xcode-select --install. macOS can use Homebrew to install the CMake and git package. Major Linux distributions package CMake, clang, and git.

Before this step, you can cd into any directory you're ok keeping code in.

{language=shell, line-numbers=off} $ git clone $ cd tmux-mem-cpu-load $ mkdir ./build $ cd ./build $ cmake .. $ make

# macOS, no sudo required
$ make install

# Linux, BSD will require sudo / root to install
$ sudo make install

If successful, you should see the output below:

{language=shell, line-numbers=off} [100%] Built target tmux-mem-cpu-load Install the project... -- Install configuration: "MinSizeRel" -- Installing: /usr/local/bin/tmux-mem-cpu-load

You can remove the source code you cloned from the computer. The compiled application is installed.

You can now add #(tmux-mem-cpu-load) to your status-left or status-right option. In the "Dressed up" example below, I use status-left and also theme it to be green:


So to apply it to your theme, you need to double check what you already have. You may have information on there you want to keep.

{language=shell, line-numbers=off} $ tmux show-option -g status-right status-right " "#{=21:pane_title}" %H:%M %d-%b-%y"

Copy what you had in response (or change, rearrange as you see fit) then add the #(tmux-mem-cpu-load) to it. You can apply the new status line in your current tmux session via $ tmux set-option -g status-right:

{language=shell, line-numbers=off} $ tmux set-option -g status-right '"#{=21:pane_title}" #(tmux-mem-cpu-load) %H:%M %d-%b-%y'

Also, note how I switched out the double quotes on either side of the option with single quotes. This is required, since there are double quotes inside.

You can do this with anything, for instance, try adding uptime. This could be done by adding #(uptime) to your status line. Typically the output is pretty long, so trim it down by doing something like this:

`#(uptime | cut -f 4-5 -d " " | cut -f 1 -d ",")``

In the next section, we go into how you can style (color) tmux.


The colors available to tmux are:

  • black, red, green, yellow, blue, magenta, cyan, white.
  • bright colors, such as brightred, brightgreen, brightyellow, brightblue, brightmagenta, brightcyan.
  • colour0 through colour255 from the 256-color set.
  • default
  • hexadecimal RGB code like #000000, #FFFFFF, similar to HTML colors.

Status line

You can use [bg=color] and [fg=color] to adjust the text color and background within for status line text. This works on status-left and status-right.

Let's say you want to style the background:

Command: $ tmux set-option status-style fg=white,bg=black

In config: status-style fg=white,bg=black

In the examples at the end of the chapter, you will see complete examples of how colors can be used.

Clock styling

You can style the color of the tmux clock via:

{lang="text", line-numbers=off} set-option -g clock-mode-colour white

Reminder: Clock mode can be opened with $ tmux clock-mode or Prefix + t. Pressing any key will exit clock mode.

Prompt colors

The benefit of wrapping your brain around this styling is you will see it message-command-style, message style and so on.

Let's try this:

{lang="shell", line-numbers=off} $ tmux set-option -ag message-style fg=yellow,blink; set-option -ag message-style bg=black

Top: default scheme for prompt. Bottom: newly-styled.

Styling while using tmux

So, you want to customize your tmux status line before you write the changes to your config file.

Start by grabbing your current status line section you want to edit, for instance:

{lang="text", line-numbers=off} $ tmux show-options -g status-left > status-left "[#S] " $ tmux show-options -g status-right > status-right " "#{=21:pane_title}" %H:%M %d-%b-%y"

Also, you can try to snip off the variable with | cut -d' ' -f2-:

{lang="text", line-numbers=off} $ tmux show-options -g status-left | cut -d' ' -f2- > "[#S] " $ tmux show-options -g status-right | cut -d' ' -f2- > " "#{=21:pane_title}" %H:%M %d-%b-%y"

Then, add the options to your configuration.

To be sure your configuration fully works, you can start it in a different server via tmux -Lrandom, verify the settings, and close it. This is helpful to make sure your config file isn't missing any styling info.

Toggling status line

The tmux status line can be hidden, as well. Turn it off:

{language=shell, line-numbers=off} $ tmux set-option status off

And, turn it on:

{language=shell, line-numbers=off} $ tmux set-option status on

The above is best for scripting, but if you're binding it to a keyboard shortcut, toggling, or reversing the current option, it can be done via omitting the on/off value:

{language=shell, line-numbers=off} $ tmux set-option status

Bind toggling status line to Prefix + q:

{language=shell, line-numbers=off} $ tmux bind-key q set-option status

Example: Default config

This is an example of the default config you see if your tmux configuration has no status styling.

{line-numbers=off} status on status-interval 15 status-justify left status-keys vi status-left "[#S] " status-left-length 10 status-left-style default status-position bottom status-right " "#{=21:pane_title}" %H:%M %d-%b-%y" status-right-length 40 status-right-style default status-style fg=black,bg=green

Example: Dressed up {#status-bar-example-dressed-up}

![](images/09-status-bar/dressed up.png)

{line-numbers=off} status on status-interval 1 status-justify centre status-keys vi status-left "#[fg=green]#H #[fg=black]• #[fg=green,bright]#(uname -r | cut -c 1-6)#[default]" status-left-length 20 status-left-style default status-position bottom status-right "#[fg=green,bg=default,bright]#(tmux-mem-cpu-load) #[fg=red,dim,bg=default]#(uptime | cut -f 4-5 -d " " | cut -f 1 -d ",") #[fg=white,bg=default]%a%l:%M:%S %p#[default] #[fg=blue]%Y-%m-%d" status-right-length 140 status-right-style default status-style fg=colour136,bg=colour235

# default window title colors
set-window-option -g window-status-fg colour244  # base0
set-window-option -g window-status-bg default

# active window title colors
set-window-option -g window-status-current-fg colour166  # orange
set-window-option -g window-status-current-bg default

Configs can print the output of an application. In this example, tmux-mem-cpu-load is providing system statistics in the right-side section of the status line.

To build tmux-mem-cpu-load, you have to install CMake and have a C++ compiler, like clang or GCC.

On Ubuntu, Debian, and Mint machines, you can do this via $ sudo apt-get install cmake build-essential. On macOS w/ brew via $ brew install cmake.


Example: Powerline

The most full-featured solution available for tmux status lines is powerline, which heavily utilizes the shell command outputs, not only to give direct system statistics, but also to generate graphical-like styling.

To get the styling to work correctly, special fonts must be installed. The easiest way to use this is to install powerline fonts, a collection of fixed width coder fonts patched to support Wingdings-like symbols.

Installation instructions are on Read the Docs. For a better idea:

{language=shell, line-numbers=off} $ pip install --user powerline-status psutil

psutil, a required dependency of powerline, is a cross-platform tool to gather system information.

Assure you properly configured python with your PATHs, and try this:

{line-numbers=off} set -g status-interval 2 set -g status-right '#(powerline tmux right)'


Configuring the status line is optional. It can use the output of programs installed on your system to give you specialized information, such as CPU, ram, and I/O usage. By default, you'll at least have a window list and a clock.

In addition, you can customize the colors of the status line, clock, and prompt. By default, it's only a green bar with dark text, so take some time to customize yours, if you want, and save it to your configuration.

In the next chapter, we will go into the command line and scripting features of tmux.

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