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//! [![github]](https://github.com/dtolnay/gflags) [![crates-io]](https://crates.io/crates/gflags) [![docs-rs]](https://docs.rs/gflags) //! //! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github //! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust //! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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 //! //! <br> //! //! Command line flag library in the style of [gflags (formerly Google //! Commandline Flags)][gflags]. //! //! [gflags]: https://gflags.github.io/gflags/ //! //! Quoting directly from the C++ gflags documentation, because the concept is //! the same here: //! //! <br> //! //! > --- //! > //! > **Commandline flags** are flags that users specify on the command line //! > when they run an executable. In the command //! > //! > ```text //! > fgrep -l -f /var/tmp/foo johannes brahms //! > ``` //! > //! > `-l` and `-f /var/tmp/foo` are the two commandline flags. (`johannes` and //! > `brahms`, which don't start with a dash, are **commandline arguments**.) //! > //! > Typically, an application lists what flags the user is allowed to pass in, //! > and what arguments they take -- in this example, `-l` takes no argument, //! > and `-f` takes a string (in particular, a filename) as an argument. Users //! > can use a library to help parse the commandline and store the flags in //! > some data structure. //! > //! > Gflags, the commandline flags library used within Google, differs from //! > other libraries, such as `getopt()`, in that flag definitions can be //! > scattered around the source code, and not just listed in one place such as //! > `main()`. In practice, this means that a single source-code file will //! > define and use flags that are meaningful to that file. Any application //! > that links in that file will get the flags, and the gflags library will //! > automatically handle that flag appropriately. //! > //! > There's significant gain in flexibility, and ease of code reuse, due to //! > this technique. //! > //! > --- //! //! <br> //! //! This style of flag registration is better suited for large scale development //! than maintaining a single central list of flags, as the central list would //! become an endless source of merge conflicts in an application developed //! simultaneously by hundreds of developers. //! //! # Defining flags //! //! Flags may be defined from any source file through the [`gflags::define!`] //! macro. There is no central list of all the flags of the application. (That's //! the point and advantage of gflags for large-scale development compared to //! other flags libraries.) //! //! [`gflags::define!`]: macro.define.html //! //! ``` //! gflags::define! { //! /// Include 'advanced' options in the menu listing. //! --big_menu = true //! } //! //! gflags::define! { //! /// Comma-separated list of languages to offer in the 'lang' menu. //! -l, --language <LANG> = "english,french,german" //! } //! # //! # fn main() {} //! ``` //! //! Flags are required to have a long name (like `--verbose`) and may optionally //! have a short name (like `-v`). Flags must have exactly one long name and at //! most one short name; multiple different aliases for the same flag is not //! supported. //! //! Flags of a type other than bool may have an optional value-placeholder like //! `<LANG>`. This is optional and purely cosmetic. It appears in help text. //! //! # Accessing flags //! //! Somewhere early in your application, call [`gflags::parse()`] to parse the //! command line. This call returns a `Vec<&str>` containing everything on the //! command line which is not a flag (these are sometimes known as positional //! arguments) in a vector. //! //! [`gflags::parse()`]: fn.parse.html //! //! After `gflags::parse()` has been called, the value of each flag is available //! in the `.flag` field of the flag's long name. //! //! ``` //! gflags::define! { //! --print-args = false //! } //! //! fn main() { //! let args = gflags::parse(); //! //! if PRINT_ARGS.flag { //! println!("args = {:?}", args); //! } //! } //! ``` //! //! As shown in this snippet, flag names may contain hyphens, in which case the //! variable through which the flag's value can be accessed has underscores in //! place of the hyphens. //! //! Additionally every flag provides a method `.is_present()` to query whether //! that flag was provided on the command line. When using flags for which a //! default value is not provided, be sure to check `.is_present()` because //! accessing `.flag` when not present will cause a panic. Note also that flags //! without a default value must specify their data type, as below. //! //! ``` //! use std::path::Path; //! //! gflags::define! { //! /// Search for patterns from the given file, with one pattern per line. //! -f, --file: &Path //! } //! //! fn main() { //! let patterns = gflags::parse(); //! //! if FILE.is_present() { //! let path = FILE.flag; //! println!("searching for patterns from file: {}", path.display()); //! } else { //! println!("searching for patterns given on command line: {:?}", patterns); //! } //! } //! ``` //! //! # Printing help //! //! There is no built-in `-h` flag for help, but you can define your own and //! call [`gflags::print_help_and_exit()`] to render the documentation of all //! flags. //! //! [`gflags::print_help_and_exit()`]: fn.print_help_and_exit.html //! //! ``` //! gflags::define! { //! -h, --help = false //! } //! //! fn main() { //! gflags::parse(); //! if HELP.flag { //! gflags::print_help_and_exit(0); //! } //! //! /* ... */ //! } //! ``` //! //! For some of the flag definitions shown in this documentation, the help text //! would be rendered as follows. //! //! ```text //! --big_menu //! Include 'advanced' options in the menu listing. //! //! -f, --file //! Search for patterns from the given file, with one pattern per line. //! //! -l, --language <LANG> //! Comma-separated list of languages to offer in the 'lang' menu. //! ``` //! //! The flags are listed in alphabetical order by long name. //! //! You will likely want to print your own content above this including the //! application name, version, author, introductory explanation, and usage //! strings. //! //! # Custom data types //! //! The `gflags::define!` macro is extensible to custom data types by providing //! an impl of [`gflags::custom::Value`] for your type. //! //! [`gflags::custom::Value`]: custom/trait.Value.html //! //! ``` //! use gflags::custom::{Arg, Error, Result, Value}; //! //! gflags::define! { //! --color <WHEN>: Color = Color::Auto //! } //! //! enum Color { //! Never, //! Always, //! Auto, //! } //! //! impl Value for Color { //! fn parse(arg: Arg) -> Result<Self> { //! match arg.get_str() { //! "never" => Ok(Color::Never), //! "always" => Ok(Color::Always), //! "auto" => Ok(Color::Auto), //! _ => Err(Error::new("invalid color")), //! } //! } //! } //! # //! # fn main() {} //! ``` #![doc(html_root_url = "https://docs.rs/gflags/0.3.5")] #![allow(clippy::needless_doctest_main)] macro_rules! eprintln { ($($tt:tt)*) => {{ use std::io::Write; let _ = std::writeln!(std::io::stderr(), $($tt)*); }}; } mod arg; mod atomic; mod dispatch; mod error; mod help; mod name; mod parse; mod state; mod token; mod value; pub mod custom; pub use crate::help::print_help_and_exit; pub use crate::parse::{parse, parse_os}; pub use crate::state::Flag; // Not public API. #[doc(hidden)] pub mod registry; #[doc(hidden)] pub use inventory; #[doc(hidden)] pub use gflags_impl as r#impl; /// Entry point for registering a flag from any source file. /// /// # Examples /// /// Please refer to the [crate level documentation](index.html) for several /// usage examples. /// /// # Grammar /// /// The complete input grammar is as follows. /// /// - Zero or more doc comments: `/// ...`. These are rendered into the /// generated help text. /// /// - Optional visibility specifier like `pub` or `pub(crate)`. This controls /// the scope of code that is allowed to see the value of this flag. By /// default flags have private visibility, which is the default in Rust. /// /// - Optional short name for the flag, like `-v`, followed by a comma. /// /// - Long name for the flag, like `--verbose`. Long name is mandatory. /// /// - Optional value-placeholder in angle brackets, like `<FILE>`. This is /// cosmetic and appears in generated help text. /// /// - Optional value type preceded by colon, like `: &str`. Type is required if /// there is no default value or the default value is not a Rust string or /// boolean or integer literal. /// /// - Optional default value preceded by equal-sign: `= "default"`. /// /// Invocation containing as few of the above as possible: /// /// ``` /// gflags::define! { /// --minimal1: bool /// } /// # /// # fn main() {} /// ``` /// /// Another way to show as few as possible. Either type or default value must be /// specified. /// /// ``` /// gflags::define! { /// --minimal2 = "default value" /// } /// # /// # fn main() {} /// ``` /// /// Showing everything at once: /// /// ``` /// # mod path { /// # pub mod to { /// # pub const DEFAULT: u32 = 0; /// # } /// # } /// # /// gflags::define! { /// /// Documentation! /// pub -m, --maximal <VALUE>: u32 = path::to::DEFAULT /// } /// # /// # fn main() {} /// ``` #[macro_export] macro_rules! define { ($($flag:tt)*) => { gflags::r#impl::define_impl! { $($flag)* } }; }