clap/examples/01a_quick_example.rs

use clap::App;

fn main() {
    // This example shows how to create an application with several arguments using usage strings, which can be
    // far less verbose that shown in 01b_QuickExample.rs, but is more readable. The downside is you cannot set
    // the more advanced configuration options using this method (well...actually you can, you'll see ;) )
    //
    // The example below is functionally identical to the 01b_quick_example.rs and 01c_quick_example.rs
    //
    // Create an application with 5 possible arguments (2 auto generated) and 2 subcommands (1 auto generated)
    //    - A config file
    //        + Uses "-c filename" or "--config filename"
    //    - An output file
    //        + A positional argument (i.e. "$ myapp output_filename")
    //    - A debug flag
    //        + Uses "-d" or "--debug"
    //        + Allows multiple occurrences of such as "-dd" (for vary levels of debugging, as an example)
    //    - A help flag (automatically generated by clap)
    //        + Uses "-h" or "--help" (Only autogenerated if you do NOT specify your own "-h" or "--help")
    //    - A version flag (automatically generated by clap)
    //        + Uses "-V" or "--version" (Only autogenerated if you do NOT specify your own "-V" or "--version")
    //    - A subcommand "test" (subcommands behave like their own apps, with their own arguments
    //        + Used by "$ myapp test" with the following arguments
    //            > A list flag
    //                = Uses "-l" (usage is "$ myapp test -l"
    //            > A help flag (automatically generated by clap
    //                = Uses "-h" or "--help" (full usage "$ myapp test -h" or "$ myapp test --help")
    //            > A version flag (automatically generated by clap
    //                = Uses "-V" or "--version" (full usage "$ myapp test -V" or "$ myapp test --version")
    //    - A subcommand "help" (automatically generated by clap because we specified a subcommand of our own)
    //        + Used by "$ myapp help" (same functionality as "-h" or "--help")
    let matches = App::new("MyApp")
        .version("1.0")
        .author("Kevin K. <kbknapp@gmail.com>")
        .about("Does awesome things")
        .license("MIT OR Apache-2.0")
        .arg("-c, --config=[FILE] 'Sets a custom config file'")
        .arg("<output> 'Sets an optional output file'")
        .arg("-d..., --debug... 'Turn debugging information on'")
        .subcommand(
            App::new("test")
                .about("does testing things")
                .arg("-l, --list 'lists test values'"),
        )
        .get_matches();

    // You can check the value provided by positional arguments, or option arguments
    if let Some(o) = matches.value_of("output") {
        println!("Value for output: {}", o);
    }

    if let Some(c) = matches.value_of("config") {
        println!("Value for config: {}", c);
    }

    // You can see how many times a particular flag or argument occurred
    // Note, only flags can have multiple occurrences
    match matches.occurrences_of("debug") {
        0 => println!("Debug mode is off"),
        1 => println!("Debug mode is kind of on"),
        2 => println!("Debug mode is on"),
        _ => println!("Don't be crazy"),
    }

    // You can check for the existence of subcommands, and if found use their
    // matches just as you would the top level app
    if let Some(matches) = matches.subcommand_matches("test") {
        // "$ myapp test" was run
        if matches.is_present("list") {
            // "$ myapp test -l" was run
            println!("Printing testing lists...");
        } else {
            println!("Not printing testing lists...");
        }
    }

    // Continued program logic goes here...
}