Crate clap

Expand description

Command Line Argument Parser for Rust

Quick Links:

Aspirations

Out of the box, users get a polished CLI experience
- Including common argument behavior, help generation, suggested fixes for users, colored output, shell completions, etc
Flexible enough to port your existing CLI interface
- However, we won’t necessarily streamline support for each use case
Reasonable parse performance
Resilient maintainership, including
- Willing to break compatibility rather than batching up breaking changes in large releases
- Leverage feature flags to keep to one active branch
- Being under WG-CLI to increase the bus factor
We follow semver and will wait about 6-9 months between major breaking changes
We will support the last two minor Rust releases (MSRV, currently 1.60.0)

While these aspirations can be at odds with fast build times and low binary size, we will still strive to keep these reasonable for the flexibility you get. Check out the argparse-benchmarks for CLI parsers optimized for other use cases.

Example

Run

$ cargo add clap --features derive

(See also feature flag reference)

Then define your CLI in main.rs:

use clap::Parser;

/// Simple program to greet a person
#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args {
   /// Name of the person to greet
   #[arg(short, long)]
   name: String,

   /// Number of times to greet
   #[arg(short, long, default_value_t = 1)]
   count: u8,
}

fn main() {
   let args = Args::parse();

   for _ in 0..args.count {
       println!("Hello {}!", args.name)
   }
}

And try it out:

$ demo --help
A simple to use, efficient, and full-featured Command Line Argument Parser

Usage: demo[EXE] [OPTIONS] --name <NAME>

Options:
  -n, --name <NAME>    Name of the person to greet
  -c, --count <COUNT>  Number of times to greet [default: 1]
  -h, --help           Print help information
  -V, --version        Print version information

$ demo --name Me
Hello Me!

(version number and .exe extension on windows replaced by placeholders)

See also the derive tutorial and reference

Augment clap:

wild for supporting wildcards (*) on Windows like you do Linux
argfile for loading additional arguments from a file (aka response files)
shadow-rs for generating Command::long_version
clap_mangen for generating man page source (roff)
clap_complete for shell completion support

CLI Helpers

Testing

trycmd: Bulk snapshot testing
snapbox: Specialized snapshot testing
assert_cmd and assert_fs: Customized testing

Documentation:

Command-line Apps for Rust book

Modules

_cookbookunstable-doc

Documentation: Cookbook

_deriveunstable-doc

Documentation: Derive Reference

_faqunstable-doc

Documentation: FAQ

_featuresunstable-doc

Documentation: Feature Flags

_tutorialunstable-doc

Documentation: Builder Tutorial

builder

Define Command line arguments

error

Error reporting

parser

Command line argument parser

Macros

arg

Create an Arg from a usage string.

commandcargo

Allows you to build the Command instance from your Cargo.toml at compile time.

crate_authorscargo

Allows you to pull the authors for the command from your Cargo.toml at compile time in the form: "author1 lastname <author1@example.com>:author2 lastname <author2@example.com>"

crate_descriptioncargo

Allows you to pull the description from your Cargo.toml at compile time.

crate_namecargo

Allows you to pull the name from your Cargo.toml at compile time.

crate_versioncargo

Allows you to pull the version from your Cargo.toml at compile time as MAJOR.MINOR.PATCH_PKGVERSION_PRE

value_parser

Select a ValueParser implementation from the intended type