highlite

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highlite is a fast, rule-based CLI highlighter for stdin and files, written in Rust.

It reads text line by line and highlights matches using ANSI colors, making it suitable for large files, streaming input, and Unix-style pipelines.

Features

• High performance: all rules are compiled into a single regex at startup
• Rule-based highlighting using keywords or regular expressions
• Supports preset ANSI colors and 24-bit RGB colors
• YAML configuration with optional recursive includes
• Designed for streaming input (stdin, pipes, large files)
• Minimal memory allocation during processing

Installation

From crates.io

cargo install highlite

From source

git clone https://github.com/sakimidare/highlite.git
cd highlite
cargo build --release

Usage

Highlight stdin:

cat example.c | highlite --config rules.yaml

Highlight a file:

highlite --config rules.yaml --file example.c

Ignore case:

highlite --config rules.yaml --ignore-case < input.txt

If stdin is a TTY, highlite will wait for input until EOF is received.

Configuration

The configuration file is written in YAML.

Basic structure

include:
  - common_optional.yaml

rules:
  - keyword: "TODO"
    color: { type: Yellow }

  - keyword: "//.*|/\\*.*\\*/"
    is_regex: true
    color: { r: 106, g: 153, b: 85 }

Rules

Each rule has the following fields:

• keyword The keyword or regular expression to match.

• is_regex (optional, default: false) Whether keyword should be treated as a regular expression.

• color The highlight color, either a preset name or an RGB value.

Colors

Preset colors

color: { type: Red }

color: { type: Yellow }

color: { type: Blue }

color: { type: Green }

color: { type: Cyan }

color: { type: Magenta }

RGB colors

color: { r: 106, g: 153, b: 85 }

Examples

See examples/cpp_example.yaml.

Design

• All rules are merged into a single regular expression.

• Each rule corresponds to a named capture group.

• Highlighting is performed in a single pass per line.

• Output buffers are reused to minimize allocations.

• This design keeps the implementation simple while maintaining high performance.

Limitations

• No nested highlighting (for example, comments inside strings).

• No cross-line strings or comments (for example: multiline /* */).

• No language-aware parsing; matching is purely regex-based.

• ANSI color output requires a compatible terminal.

License

This project is licensed under the GNU General Public License v3.0.

Contributing

Issues and pull requests are welcome.