rust cli clap

clap for CLI argument parsing with derive macros

Marcus Chen Jan 2026

1 tab

use clap::Parser;

#[derive(Parser, Debug)]
#[command(author, version, about)]
struct Args {
    #[arg(short, long)]
    input: String,

    #[arg(short, long, default_value = "output.txt")]
    output: String,

    #[arg(short, long)]
    verbose: bool,
}

fn main() {
    let args = Args::parse();
    println!("{:?}", args);
}

1 file · rust Explain with highlit

For CLI tools, clap is the de facto standard. Version 4+ supports derive macros, letting you define arguments as a struct with attributes. The library auto-generates help text, validates inputs, and supports subcommands. I annotate fields with #[arg(short, long)] for flags, #[command(subcommand)] for nested commands, and value_parser for type checking. Clap handles --help, --version, and error messages automatically. The resulting code is declarative and self-documenting. For complex CLIs with multiple levels (like git or cargo), clap's subcommand support scales well. The compile-time safety means typos in argument names are caught early, and the generated help is always in sync with the code.