Coloring and theming in Nu

Many parts of Nushell’s interface can have their color customized. All of these can be set in the config.nu configuration file. If you see the hash/hashtag/pound mark # in the config file it means the text after it is commented out.

1. table borders
2. primitive values
3. shapes (this is the command line syntax)
4. prompt
5. LS_COLORS

Table borders

Table borders are controlled by the table_mode setting in config.nu. Here is an example:

> let $config = {
    table_mode: rounded
}

Here are the current options for table_mode:

• rounded # of course, this is the best one 😃
• basic
• compact
• compact_double
• light
• thin
• with_love
• reinforced
• heavy
• none
• other

Color symbologies

• r - normal color red’s abbreviation
• rb - normal color red’s abbreviation with bold attribute
• red - normal color red
• red_bold - normal color red with bold attribute
• "#ff0000" - “#hex” format foreground color red (quotes are required)
• { fg: "#ff0000" bg: "#0000ff" attr: b } - “full #hex” format foreground red in “#hex” format with a background of blue in “#hex” format with an attribute of bold abbreviated.

attributes

normal colors and abbreviations

"#hex" format

The “#hex” format is one way you typically see colors represented. It’s simply the # character followed by 6 characters. The first two are for red, the second two are for green, and the third two are for blue. It’s important that this string be surrounded in quotes, otherwise Nushell thinks it’s a commented out string.

Example: The primary red color is "#ff0000" or "#FF0000". Upper and lower case in letters shouldn’t make a difference.

This "#hex" format allows us to specify 24-bit truecolor tones to different parts of Nushell.

full "#hex" format

The full "#hex" format is a take on the "#hex" format but allows one to specify the foreground, background, and attributes in one line.

Example: { fg: "#ff0000" bg: "#0000ff" attr: b }

• foreground of red in “#hex” format
• background of blue in “#hex” format
• attribute of bold abbreviated

Primitive values

Primitive values are things like int and string. Primitive values and shapes can be set with a variety of color symbologies seen above.

This is the current list of primitives. Not all of these are configurable. The configurable ones are marked with *.

special “primitives” (not really primitives but they exist solely for coloring)

Here’s a small example of changing some of these values.

> let config = {
    color_config: {
        separator: purple
        leading_trailing_space_bg: "#ffffff"
        header: gb
        date: wd
        filesize: c
        row_index: cb
        bool: red
        int: green
        duration: blue_bold
        range: purple
        float: red
        string: white
        nothing: red
        binary: red
        cellpath: cyan
        hints: dark_gray
    }
}

Here’s another small example using multiple color syntaxes with some comments.

> let config = {
    color_config: {
        separator: "#88b719" # this sets only the foreground color like PR #486
        leading_trailing_space_bg: white # this sets only the foreground color in the original style
        header: { # this is like PR #489
            fg: "#B01455", # note, quotes are required on the values with hex colors
            bg: "#ffb900",# note, commas are not required, it could also be all on one line
            attr: bli # note, there are no quotes around this value. it works with or without quotes
        }
        date: "#75507B"
        filesize: "#729fcf"
        row_index: {
            # note, that this is another way to set only the foreground, no need to specify bg and attr
            fg: "#e50914"
        }
    }
}

Shape values

As mentioned above, shape is a term used to indicate the syntax coloring.

Here’s the current list of flat shapes.

Here’s a small example of how to apply color to these items. Anything not specified will receive the default color.

> let $config = {
    color_config: {
        shape_garbage: { fg: "#FFFFFF" bg: "#FF0000" attr: b}
        shape_bool: green
        shape_int: { fg: "#0000ff" attr: b}
    }
}

Prompt configuration and coloring

The Nushell prompt is configurable through these environment variables:

• PROMPT_COMMAND: Code to execute for setting up the prompt (block)
• PROMPT_COMMAND_RIGHT: Code to execute for setting up the RIGHT prompt (block) (see oh-my.nu in nu_scripts)
• PROMPT_INDICATOR = “〉”: The indicator printed after the prompt (by default “>”-like Unicode symbol)
• PROMPT_INDICATOR_VI_INSERT = “: “
• PROMPT_INDICATOR_VI_NORMAL = “v “
• PROMPT_MULTILINE_INDICATOR = “::: “

Example: For a simple prompt one could do this. Note that PROMPT_COMMAND requires a block whereas the others require a string.

> let-env PROMPT_COMMAND = { build-string (date now | date format '%m/%d/%Y %I:%M:%S%.3f') ': ' (pwd | path basename) }

If you don’t like the default PROMPT_INDICATOR you could change it like this.

> let-env PROMPT_INDICATOR = "> "

Coloring of the prompt is controlled by the block in PROMPT_COMMAND where you can write your own custom prompt. We’ve written a slightly fancy one that has git statuses located in the nu_scripts repo (opens new window).

LS_COLORS colors for the ls command

Nushell will respect and use the LS_COLORS environment variable setting on Mac, Linux, and Windows. This setting allows you to define the color of file types when you do a ls. For instance, you can make directories one color, _.md markdown files another color, _.toml files yet another color, etc. There are a variety of ways to color your file types.

There’s an exhaustive list here (opens new window), which is overkill, but gives you an rudimentary understanding of how to create a ls_colors file that dircolors can turn into a LS_COLORS environment variable.

This (opens new window) is a pretty good introduction to LS_COLORS. I’m sure you can find many more tutorials on the web.

I like the vivid application and currently have it configured in my config.nu like this. You can find vivid here (opens new window).

let-env LS_COLORS = (vivid generate molokai | str trim)

If LS_COLORS is not set, nushell will default to a builtin LS_COLORS setting, based on 8-bit (extended) ANSI colors.

Theming

Theming combines all the coloring above. Here’s a quick example of one we put together quickly to demonstrate the ability to theme. This is a spin on the base16 themes that we see so widespread on the web.

The key to making theming work is to make sure you specify all themes and colors you’re going to use in the config.nu file before you declare the let config = line.

# let's define some colors
let base00 = "#181818" # Default Background
let base01 = "#282828" # Lighter Background (Used for status bars, line number and folding marks)
let base02 = "#383838" # Selection Background
let base03 = "#585858" # Comments, Invisibles, Line Highlighting
let base04 = "#b8b8b8" # Dark Foreground (Used for status bars)
let base05 = "#d8d8d8" # Default Foreground, Caret, Delimiters, Operators
let base06 = "#e8e8e8" # Light Foreground (Not often used)
let base07 = "#f8f8f8" # Light Background (Not often used)
let base08 = "#ab4642" # Variables, XML Tags, Markup Link Text, Markup Lists, Diff Deleted
let base09 = "#dc9656" # Integers, Boolean, Constants, XML Attributes, Markup Link Url
let base0a = "#f7ca88" # Classes, Markup Bold, Search Text Background
let base0b = "#a1b56c" # Strings, Inherited Class, Markup Code, Diff Inserted
let base0c = "#86c1b9" # Support, Regular Expressions, Escape Characters, Markup Quotes
let base0d = "#7cafc2" # Functions, Methods, Attribute IDs, Headings
let base0e = "#ba8baf" # Keywords, Storage, Selector, Markup Italic, Diff Changed
let base0f = "#a16946" # Deprecated, Opening/Closing Embedded Language Tags, e.g. <?php ?>
# we're creating a theme here that uses the colors we defined above.
let base16_theme = {
    separator: $base03
    leading_trailing_space_bg: $base04
    header: $base0b
    date: $base0e
    filesize: $base0d
    row_index: $base0c
    bool: $base08
    int: $base0b
    duration: $base08
    range: $base08
    float: $base08
    string: $base04
    nothing: $base08
    binary: $base08
    cellpath: $base08
    hints: dark_gray
    # shape_garbage: { fg: $base07 bg: $base08 attr: b} # base16 white on red
    # but i like the regular white on red for parse errors
    shape_garbage: { fg: "#FFFFFF" bg: "#FF0000" attr: b}
    shape_bool: $base0d
    shape_int: { fg: $base0e attr: b}
    shape_float: { fg: $base0e attr: b}
    shape_range: { fg: $base0a attr: b}
    shape_internalcall: { fg: $base0c attr: b}
    shape_external: $base0c
    shape_externalarg: { fg: $base0b attr: b}
    shape_literal: $base0d
    shape_operator: $base0a
    shape_signature: { fg: $base0b attr: b}
    shape_string: $base0b
    shape_filepath: $base0d
    shape_globpattern: { fg: $base0d attr: b}
    shape_variable: $base0e
    shape_flag: { fg: $base0d attr: b}
    shape_custom: {attr: b}
}
# now let's apply our regular config settings but also apply the "color_config:" theme that we specified above.
let config = {
  filesize_metric: true
  table_mode: rounded # basic, compact, compact_double, light, thin, with_love, rounded, reinforced, heavy, none, other
  use_ls_colors: true
  color_config: $base16_theme # <-- this is the theme
  use_grid_icons: true
  footer_mode: always #always, never, number_of_rows, auto
  animate_prompt: false
  float_precision: 2
  use_ansi_coloring: true
  filesize_format: "b" # b, kb, kib, mb, mib, gb, gib, tb, tib, pb, pib, eb, eib, zb, zib, auto
  edit_mode: emacs # vi
  max_history_size: 10000
  log_level: error
}

if you want to go full-tilt on theming, you’ll want to theme all the items I mentioned at the very beginning, including LS_COLORS, and the prompt. Good luck!