How to Use the Command 'chroma' (with Examples)

Chroma is a versatile and powerful syntax highlighter designed to help developers format and present source code in a visually appealing and readable manner. By detecting the programming language used in a file based on the file extension, Chroma applies distinct color schemes to different code elements such as keywords, variables, and strings, making it easier for programmers to read and understand the code structure. It’s widely used in software development, documentation, and educational materials for enhancing code readability.

Use Case 1: Highlight Source Code from a File with the Python Lexer and Output to stdout

Code:

chroma --lexer python path/to/source_file.py

Motivation:

This use case is ideal when you want to quickly preview or print highlighted Python code directly to the terminal. Developers often need to inspect or share snippets of code with syntax highlighting, allowing others to easily interpret the elements of the code such as functions, classes, and conditions.

Explanation:

• --lexer python: This argument specifies that the Python lexer should be used, telling Chroma to parse and highlight the input code according to Python syntax rules.
• path/to/source_file.py: This indicates the path to the Python source file you want to highlight. Chroma reads this file to process and display it with syntax highlighting.

Example Output:

When you run this command, you will see your Python code in the terminal with different colors representing different syntactical features like keywords, strings, and comments.

Use Case 2: Highlight Source Code from a File with the Go Lexer and Output to an HTML File

Code:

chroma --lexer go --formatter html path/to/source_file.go > path/to/target_file.html

Motivation:

Outputting highlighted code to an HTML file is useful when you want to integrate syntax-highlighted code into a webpage or documentation. This allows viewers to see the source code with consistent syntax highlighting, making it easier to read and aesthetically pleasing on the web.

Explanation:

• --lexer go: Specifies that the Go language lexer should be used, which instructs Chroma to recognize and highlight Go language syntax.
• --formatter html: Sets the output format to HTML, which is appropriate for web publishing or sharing in environments that support HTML formatting.
• path/to/source_file.go: The path to the Go source file containing the code you want to highlight.
• > path/to/target_file.html: Redirects the terminal output to the specified HTML file, saving your highlighted code in this format for future use.

Example Output:

The resulting HTML file displays your Go code with HTML-back formatting, maintaining all syntax elements in well-defined color schemes, making it ready for embedding in a web page.

Use Case 3: Highlight Source Code from stdin with the C++ Lexer and Output to an SVG File, Using the Monokai Style

Code:

command | chroma --lexer c++ --formatter svg --style monokai > path/to/target_file.svg

Motivation:

This use case is beneficial when you want to convert C++ code to a stylized SVG image, perhaps for inclusion in presentations or printed materials. The Monokai style is a popular and visually distinctive theme that enhances the readability and aesthetics of your code.

Explanation:

• command: A placeholder for the shell command that outputs C++ code to stdin, which Chroma will then process.
• --lexer c++: Directs Chroma to use the C++ lexer, allowing it to accurately recognize and highlight C++ code syntax.
• --formatter svg: Specifies that the output format should be SVG, a vector-based image format suitable for high-quality, scalable images.
• --style monokai: Applies the Monokai color style to the output, a widely-used color scheme known for its dark background and vibrant colors.
• > path/to/target_file.svg: Directs the formatted and highlighted output to an SVG file, storing it as an image.

Example Output:

The SVG file contains your C++ code with Monokai-style highlighting, which can be viewed in an SVG-compatible viewer or incorporated into documents and presentations.

Use Case 4: List Available Lexers, Styles, and Formatters

Code:

chroma --list

Motivation:

This command is critical for exploring the capabilities of Chroma, allowing developers to view all available lexers, styles, and formatters. Understanding these options is helpful for selecting the best syntax highlighter configuration based on the programming language and output format you desire.

Explanation:

• --list: This option commands Chroma to display a comprehensive list of all lexers (for language support), styles (color themes), and formatters (output formats) that it supports, providing users with broader insight into Chroma’s functionality.

Example Output:

Running this command will present a list in the terminal showing available lexers for different programming languages, styles for color themes, and formatters for output options, helping you choose the right settings for your highlighting needs.

Conclusion:

Chroma is a flexible and powerful tool for developers who need to apply syntax highlighting to their code in various formats across different programming languages. Each use case proven here illustrates the ease with which Chroma can be adapted to meet specific needs, from direct terminal previews to creating rich-formatted outputs suitable for web or presentation use. By understanding these use cases, developers can maximize their code readability and presentation quality in any environment.