Similar to the examples in the previous chapter, we have a parser for arguments. It has the following declaration:

let matches = App::new(crate_name!())
    .version(crate_version!())
    .author(crate_authors!())
    .about(crate_description!())
    .setting(AppSettings::SubcommandRequired)
    .arg(
        Arg::with_name("database")
        .short("d")
        .long("db")
        .value_name("FILE")
        .help("Sets a file name of a database")
        .takes_value(true),
        )
    .subcommand(SubCommand::with_name(CMD_ADD).about("add user to the table")
                .arg(Arg::with_name("NAME")
                     .help("Sets the name of a user")
                     .required(true)
                     .index(1))
                .arg(Arg::with_name("EMAIL")
                     .help("Sets the email of a user")
                     .required(true)
                     .index(2)))
    .subcommand(SubCommand::with_name(CMD_LIST).about("prints a list with users"))
    .get_matches();

We can get --database arguments with a path to a database file. The  add subcommand requires two arguments—NAME with the name of a user, and EMAIL with their email. The list subcommand doesn't require extra arguments and will print a list of users.