Pastel

Terminal output styling with intuitive and clean API that doesn't monkey patch String class.

Pastel is minimal and focused to work in all terminal emulators.

screenshot

Pastel provides independent coloring component for TTY toolkit.

Features

Doesn't monkey patch String
Intuitive and expressive API
Minimal and focused to work on all terminal emulators
Auto-detection of color support
Allows nested styles
Performant

Installation

Add this line to your application's Gemfile:

gem "pastel"

And then execute:

$ bundle

Or install it yourself as:

$ gem install pastel

1. Usage
2. Interface
3. Supported Colors
4. Environment
5. Command line

1 Usage

Pastel provides a simple, minimal and intuitive API for styling your strings:

pastel = Pastel.new

puts pastel.red("Unicorns!")

Pastel doesn't print the colored string out, just returns it, you'll have to print it yourself.

You can compose multiple styles through chainable API:

pastel.red.on_green.bold("Unicorns!")

It allows you to combine styled strings with unstyled ones:

pastel.red("Unicorns") + " will rule " + pastel.green("the World!")

It supports variable number of arguments:

pastel.red("Unicorns", "are", "running", "everywhere!")

You can also nest styles as follows:

pastel.red("Unicorns ", pastel.on_green("everywhere!"))

Nesting is smart enough to know where one color ends and another one starts:

pastel.red("Unicorns " + pastel.green("everywhere") + pastel.on_yellow("!"))

You can also nest styles inside blocks:

pastel.red.on_green("Unicorns") {
  green.on_red("will ", "dominate") {
    yellow("the world!")
  }
}

When dealing with multiline strings you can set eachline option(more info see eachline):

pastel = Pastel.new(eachline: "\n")

You can also predefine needed styles and reuse them:

error    = pastel.red.bold.detach
warning  = pastel.yellow.detach

puts error.("Error!")
puts warning.("Warning")

If your output is redirected to a file, you probably don't want Pastel to add color to your text. See https://github.com/piotrmurach/pastel#210-enabled for a way to easily accomplish this.

Pastel has companion library called pastel-cli that allows you to style text in terminal via pastel executable:

$ pastel green "Unicorns & rainbows!"

2 Interface

2.1 Color

pastel.<color>[.<color>...](string, [string...])

Color styles are invoked as method calls with a string argument. A given color can take any number of strings as arguments. Then it returns a colored string which isn't printed out to terminal. You need to print it yourself if you need to. This is done so that you can save it as a string, pass to something else, send it to a file handle and so on.

pastel.red("Unicorns ", pastel.bold.underline("everywhere"), "!")

Please refer to 3. Supported Colors section for full list of supported styles.

2.2 Decorate

This method is a lower level string styling call that takes as the first argument the string to style followed by any number of color attributes, and returns string wrapped in styles.

pastel.decorate("Unicorn", :green, :on_blue, :bold)

This method will be useful in situations where colors are provided as a list of parameters that have been generated dynamically.

2.3 Undecorate

It performs the opposite to decorate method by turning color escape sequences found in the string into a list of hash objects corresponding with the attribute names set by those sequences. Depending on the parsed string, each hash object may contain :foreground, :background, :text and/or :style keys.

pastel.undecorate("\e[32mfoo\e[0m \e[31mbar\e[0m")
# => [{foreground: :green, text: "foo"}, {text: " "}, {foreground: :red, text: "bar"}]

To translate the color name into sequence use lookup

2.4 Detach

The detach method allows to keep all the associated colors with the detached instance for later reference. This method is useful when detached colors are being reused frequently and thus shorthand version is preferred. The detached object can be invoked using call method or it's shorthand .(), as well as array like access []. For example, the following are equivalent examples of detaching colors:

notice = pastel.blue.bold.detach

notice.call("Unicorns running")
notice.("Unicorns running")
notice["Unicorns running"]

2.5 Strip

Strip only color sequence characters from the provided strings and preserve any movement codes or other escape sequences. The return value will be either array of modified strings or a single string. The arguments are not modified.

pastel.strip("\e[1A\e[1m\e[34mbold blue text\e[0m")  # => "\e[1Abold blue text"

2.6 Styles

To get a full list of supported styles with the corresponding color codes do:

pastel.styles

2.7 Lookup

To perform translation of color name into ansi escape code use lookup:

pastel.lookup(:red)   # => "\e[31m"
pastel.lookup(:reset) # => "\e[0m"

2.8 Valid?

Determine whether a color or a list of colors are valid. valid? takes one or more attribute strings or symbols and returns true if all attributes are known and false otherwise.

pastel.valid?(:red, :blue) # => true
pastel.valid?(:unicorn)    # => false

2.9 Colored?

In order to determine if string has color escape codes use colored? like so

pastel.colored?("\e[31mcolorful\e[0m")  # => true

2.10 Enabled?

In order to detect if your terminal supports coloring do:

pastel.enabled?   # => false

In cases when the color support is not provided no styling will be applied to the colored string. Moreover, you can force Pastel to always print out string with coloring switched on:

pastel = Pastel.new(enabled: true)
pastel.enabled?   # => true

If you are outputting to stdout or stderr, and want to suppress color if output is redirected to a file, you can set the enabled attribute dynamically, as in:

stdout_pastel = Pastel.new(enabled: $stdout.tty?)
stderr_pastel = Pastel.new(enabled: $stderr.tty?)

2.11 Eachline

Normally Pastel colors string by putting color codes at the beginning and end of the string, but if you provide eachline option set to some string, that string will be considered the line delimiter. Consequently, each line will be separately colored with escape sequence and reset code at the end. This option is desirable if the output string contains newlines and you're using background colors. Since color code that spans more than one line is often interpreted by terminal as providing background for all the lines that follow. This in turn may cause programs such as pagers to spill the colors throughout the text. In most cases you will want to set eachline to \n character like so:

pastel = Pastel.new(eachline: "\n")
pastel.red("foo\nbar")  # => "\e[31mfoo\e[0m\n\e[31mbar\e[0m"

2.12 Alias Color

In order to setup an alias for standard colors do:

pastel.alias_color(:funky, :red, :bold)

From that point forward, :funky alias can be passed to decorate, valid? with the same meaning as standard colors:

pastel.funky.on_green("unicorn")   # => will use :red, :bold color

This method allows you to give more meaningful names to existing colors.

You can also use the PASTEL_COLORS_ALIASES environment variable (see Environment) to specify aliases.

Note: Aliases are global and affect all callers in the same process.

3 Supported Colors

Pastel works with terminal emulators that support minimum sixteen colors. It provides 16 basic colors and 8 styles with further 16 bright color pairs. The corresponding bright color is obtained by prepending the bright to the normal color name. For example, color red will have bright_red as its pair.

The variant with on_ prefix will style the text background color.

The foreground colors:

black
red
green
yellow
blue
magenta
cyan
white
bright_black
bright_red
bright_green
bright_yellow
bright_blue
bright_magenta
bright_cyan
bright_white

The background colors:

on_black
on_red
on_green
on_yellow
on_blue
on_magenta
on_cyan
on_white
on_bright_black
on_bright_red
on_bright_green
on_bright_yellow
on_bright_blue
on_bright_magenta
on_bright_cyan
on_bright_white

Generic styles:

clear
bold
dim
italic
underline
inverse
hidden
strikethrough

4 Environment

4.1 PASTEL_COLORS_ALIASES

This environment variable allows you to specify custom color aliases at runtime that will be understood by Pastel. The environment variable is read and used when the instance of Pastel is created. You can also use alias_color to create aliases.

Only alphanumeric and _ and . are allowed in the alias names with the following format:

PASTEL_COLORS_ALIASES="newcolor_1=red,newcolor_2=on_green,funky=red.bold"

5. Command line

You can also install pastel-cli to use pastel executable in terminal:

$ pastel green 'Unicorns & rainbows!'

Contributing

Fork it ( https://github.com/piotrmurach/pastel/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

Code of Conduct

Everyone interacting in the Pastel project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.