The Rust Pattern That Finally Made My CLI Tools Fast, Clean, and Maintainable

How I used structopt/clap derive patterns, modules, and error enums to simplify complex tool-building.

Michael Preston

5 min read

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3 days ago

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1. When My CLI Tools Became Too Messy to Maintain

I started writing Rust CLI tools with a simple goal: speed. Rust gave me that instantly. But the moment my tools grew beyond a few subcommands, things fell apart — messy match blocks, scattered parsing logic, inconsistent error handling, and a folder structure that felt more like a junk drawer than an actual codebase.

The breakthrough came when I adopted a pattern combining structopt/clap derive macros, modular command separation, and a single unified error enum. That pairing finally brought clarity, velocity, and long-term maintainability.

Before I cleaned things up, my CLI looked like this:

fn main() {
    let args: Vec<String> = std::env::args().collect();
    match args.get(1).map(|s| s.as_str()) {
        Some("list") => list_files(),
        Some("copy") => copy_file(args.get(2), args.get(3)),
        Some("delete") => delete_file(args.get(2)),
        _ => println!("Unknown command"),
    }
}