Rust Command Line Argument Parsers

Clap is the most comprehensive Rust argument-parsing library, offering a derive macro for struct-based parsing, subcommand support, automatic help generation, value validation, shell completion generation, and extensive customization — exactly what you need for a CLI application.

Structopt is a Rust library that lets you define CLI arguments as a struct with a derive macro, providing automatic help generation, subcommand support, and default values, which matches the request for a command-line argument parsing library; however, it may not include built-in shell completion generation or custom error messages as part of its core feature set.

argh is a Rust derive-based argument parsing library that supports struct-based parsing, subcommands, and automatic help generation, which directly fits the search for a Rust CLI argument parser — though its focus on minimal code size means it lacks built-in shell completion generation and has limited error customization compared to more full-featured options.