Building a Command Line Tool: grep Implementation

This chapter demonstrates Rust concepts through building a grep clone. The project combines:

  • Code organization and module system
  • Collections (vectors, strings)
  • Error handling patterns
  • Traits and lifetimes
  • Testing strategies
  • Closures and iterators (introduced here, detailed in Chapter 13)

Project Overview

We’ll build minigrep - a simplified version of the Unix grep utility that searches files for text patterns. The tool will:

  • Accept command line arguments (query string and file path)
  • Read file contents
  • Filter matching lines
  • Handle errors gracefully
  • Support case-insensitive search via environment variables
  • Write errors to stderr, results to stdout

This implementation showcases Rust’s performance, safety, and cross-platform capabilities for CLI tools, while demonstrating idiomatic patterns for real-world applications.