extern crate clap; use clap::{App, Arg}; fn main() { // Args describe a possible valid argument which may be supplied by the user at runtime. There // are three different types of arguments (flags, options, and positional) as well as a fourth // special type of argument, called SubCommands (which will be discussed separately). // // Args are described in the same manner as Apps using the "builder pattern" with multiple // methods describing various settings for the individual arguments. Or by supplying a "usage" // string. Both methods have their pros and cons. // // Arguments can be added to applications in two manners, one at a time with the arg(), and // arg_from_usage() method, or multiple arguments at once via a Vec inside the args() method, // or a single &str describing multiple Args (one per line) supplied to args_from_usage(). // // There are various options which can be set for a given argument, some apply to any of the // three types of arguments, some only apply one or two of the types. *NOTE* if you set // incompatible options on a single argument, clap will panic! at runtime. This is by design, // so that you know right away an error was made by the developer, not the end user. // // # Help and Version // clap automatically generates a help and version flag for you, unless you specify your // own. By default help uses "-h" and "--help", and version uses "-V" and "--version". You can // safely override "-V" and "-h" to your own arguments, and "--help" and "--version" will still // be automatically generated for you. let matches = App::new("MyApp") // All application settings go here... // A simple "Flag" argument example (i.e. "-d") using the builder pattern .arg(Arg::with_name("debug") .help("turn on debugging information") .short("d")) // Two arguments, one "Option" argument (i.e. one that takes a value) such // as "-c some", and one positional argument (i.e. "myapp some_file") .args(&[ Arg::with_name("config") .help("sets the config file to use") .takes_value(true) .short("c") .long("config"), Arg::with_name("input") .help("the input file to use") .index(1) .required(true) ]) // *Note* the following two examples are convenience methods, if you wish // to still get the full configurability of Arg::with_name() and the readability // of arg_from_usage(), you can instantiate a new Arg with Arg::from_usage() and // still be able to set all the additional properties, just like Arg::with_name() // // // One "Flag" using a usage string .arg_from_usage("--license 'display the license file'") // Two args, one "Positional", and one "Option" using a usage string .args_from_usage("[output] 'Supply an output file to use' -i, --int=[IFACE] 'Set an interface to use'") .get_matches(); // Here are some examples of using the arguments defined above. Keep in mind that this is only // an example, and may be somewhat contrived // // First we check if debugging should be on or not println!("Debugging mode is: {}", if matches.is_present("debug") { "ON" } else { "OFF" }); // Next we print the config file we're using, if any was defined with either -c or // --config if let Some(config) = matches.value_of("config") { println!("A config file was passed in: {}", config); } // Let's print the file the user passed in. We can use .unwrap() here becase the arg is // required, and parsing would have failed if the user forgot it println!("Using input file: {}", matches.value_of("input").unwrap()); // We could continue checking for and using arguments in this manner, such as "license", // "output", and "interface". Keep in mind that "output" and "interface" are optional, so you // shouldn't call .unwrap(). Instead, prefer using an 'if let' expression as we did with // "config" }