// Contributing // // New example code: // - Please update the corresponding section in the derive tutorial // - Building: They must be added to `Cargo.toml` with the appropriate `required-features`. // - Testing: Ensure there is a markdown file with [trycmd](https://docs.rs/trycmd) syntax // // See also the general CONTRIBUTING //! # Documentation: Builder Tutorial //! //! 1. [Quick Start](#quick-start) //! 2. [Configuring the Parser](#configuring-the-parser) //! 3. [Adding Arguments](#adding-arguments) //! 1. [Positionals](#positionals) //! 2. [Options](#options) //! 3. [Flags](#flags) //! 4. [Subcommands](#subcommands) //! 5. [Defaults](#defaults) //! 4. Validation //! 1. [Enumerated values](#enumerated-values) //! 2. [Validated values](#validated-values) //! 3. [Argument Relations](#argument-relations) //! 4. [Custom Validation](#custom-validation) //! 5. [Testing](#testing) //! 6. [Next Steps](#next-steps) //! //! See also //! - [FAQ: When should I use the builder vs derive APIs?][crate::_faq#when-should-i-use-the-builder-vs-derive-apis] //! - The [cookbook][crate::_cookbook] for more application-focused examples //! //! ## Quick Start //! //! You can create an application with several arguments using usage strings. //! //! First, ensure `clap` is available: //! ```console //! $ cargo add clap //! ``` //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/01_quick.rs")] //! ``` //! #![doc = include_str!("../examples/tutorial_builder/01_quick.md")] //! //! ## Configuring the Parser //! //! You use [`Command`][crate::Command] to start building a parser. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/02_apps.rs")] //! ``` //! #![doc = include_str!("../examples/tutorial_builder/02_apps.md")] //! //! You can use [`command!()`][crate::command!] to fill these fields in from your `Cargo.toml` //! file. **This requires the [`cargo` feature flag][crate::_features].** //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/02_crate.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/02_crate.md")] //! //! You can use [`Command`][crate::Command] methods to change the application level behavior of //! clap, like [`Command::next_line_help`]. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/02_app_settings.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/02_app_settings.md")] //! //! ## Adding Arguments //! //! ### Positionals //! //! You can have users specify values by their position on the command-line: //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_03_positional.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_03_positional.md")] //! //! Note that the default [`ArgAction`][crate::ArgAction] is [`Set`][crate::ArgAction::Set]. To //! accept multiple values, override the [action][Arg::action] with [`Append`][crate::ArgAction::Append]: //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_03_positional_mult.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_03_positional_mult.md")] //! //! ### Options //! //! You can name your arguments with a flag: //! - Order doesn't matter //! - They can be optional //! - Intent is clearer //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_02_option.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_02_option.md")] //! //! Note that the default [`ArgAction`][crate::ArgAction] is [`Set`][crate::ArgAction::Set]. To //! accept multiple occurrences, override the [action][Arg::action] with [`Append`][crate::ArgAction::Append]: //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_02_option_mult.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_02_option_mult.md")] //! //! ### Flags //! //! Flags can also be switches that can be on/off: //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_01_flag_bool.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_01_flag_bool.md")] //! //! To accept multiple flags, use [`Count`][crate::ArgAction::Count]: //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_01_flag_count.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_01_flag_count.md")] //! //! ### Subcommands //! //! Subcommands are defined as [`Command`][crate::Command]s that get added via //! [`Command::subcommand`][crate::Command::subcommand]. Each instance of a Subcommand can have its //! own version, author(s), Args, and even its own subcommands. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_04_subcommands.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_04_subcommands.md")] //! //! ### Defaults //! //! We've previously showed that arguments can be [`required`][crate::Arg::required] or optional. //! When optional, you work with a `Option` and can `unwrap_or`. Alternatively, you can set //! [`Arg::default_value`][crate::Arg::default_value]. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/03_05_default_values.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/03_05_default_values.md")] //! //! ## Validation //! //! By default, arguments are assumed to be `String`s and only UTF-8 validation is performed. //! //! ### Enumerated values //! //! If you have arguments of specific values you want to test for, you can use the //! [`PossibleValuesParser`][crate::builder::PossibleValuesParser] or [`Arg::value_parser(["val1", //! ...])`][crate::Arg::value_parser] for short. //! //! This allows you specify the valid values for that argument. If the user does not use one of //! those specific values, they will receive a graceful exit with error message informing them //! of the mistake, and what the possible valid values are //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_01_possible.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_01_possible.md")] //! //! When enabling the [`derive` feature][crate::_features], you can use //! [`ValueEnum`][crate::ValueEnum] to take care of the boiler plate for you, giving the same //! results. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_01_enum.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_01_enum.md")] //! //! ### Validated values //! //! More generally, you can validate and parse into any data type with [`Arg::value_parser`]. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_02_parse.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_02_parse.md")] //! //! A [custom parser][TypedValueParser] can be used to improve the error messages or provide additional validation: //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_02_validate.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_02_validate.md")] //! //! See [`Arg::value_parser`][crate::Arg::value_parser] for more details. //! //! ### Argument Relations //! //! You can declare dependencies or conflicts between [`Arg`][crate::Arg]s or even //! [`ArgGroup`][crate::ArgGroup]s. //! //! [`ArgGroup`][crate::ArgGroup]s make it easier to declare relations instead of having to list //! each individually, or when you want a rule to apply "any but not all" arguments. //! //! Perhaps the most common use of [`ArgGroup`][crate::ArgGroup]s is to require one and *only* one //! argument to be present out of a given set. Imagine that you had multiple arguments, and you //! want one of them to be required, but making all of them required isn't feasible because perhaps //! they conflict with each other. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_03_relations.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_03_relations.md")] //! //! ### Custom Validation //! //! As a last resort, you can create custom errors with the basics of clap's formatting. //! //! ```rust #![doc = include_str!("../examples/tutorial_builder/04_04_custom.rs")] //! ``` #![doc = include_str!("../examples/tutorial_builder/04_04_custom.md")] //! //! ## Testing //! //! clap reports most development errors as `debug_assert!`s. Rather than checking every //! subcommand, you should have a test that calls //! [`Command::debug_assert`][crate::Command::debug_assert]: //! ```rust,no_run #![doc = include_str!("../examples/tutorial_builder/05_01_assert.rs")] //! ``` //! //! ## Next Steps //! //! - [Cookbook][crate::_cookbook] for application-focused examples //! - Explore more features in the [API reference][super] //! //! For support, see [Discussions](https://github.com/clap-rs/clap/discussions) #![allow(unused_imports)] use crate::builder::Arg; use crate::builder::ArgGroup; use crate::builder::Command; use crate::builder::PossibleValue; use crate::builder::TypedValueParser;