[dependencies]
structopt = "0.3"

use std::path::PathBuf;
use structopt::StructOpt;
/// A basic example
#[derive(StructOpt, Debug)]
#[structopt(name = "basic")]
struct Opt {
    // A flag, true if used in the command line. Note doc comment will
    // be used for the help message of the flag. The name of the
    // argument will be, by default, based on the name of the field.
    /// Activate debug mode
    #[structopt(short, long)]
    debug: bool,
    // The number of occurrences of the `v/verbose` flag
    /// Verbose mode (-v, -vv, -vvv, etc.)
    #[structopt(short, long, parse(from_occurrences))]
    verbose: u8,
    /// Set speed
    #[structopt(short, long, default_value = "42")]
    speed: f64,
    /// Output file
    #[structopt(short, long, parse(from_os_str))]
    output: PathBuf,
    // the long option will be translated by default to kebab case,
    // i.e. `--nb-cars`.
    /// Number of cars
    #[structopt(short = "c", long)]
    nb_cars: Option<i32>,
    /// admin_level to consider
    #[structopt(short, long)]
    level: Vec<String>,
    /// Files to process
    #[structopt(name = "FILE", parse(from_os_str))]
    files: Vec<PathBuf>,
}
fn main() {
    let opt = Opt::from_args();
    println!("{:#?}", opt);
}

$ ./basic
error: The following required arguments were not provided:
    --output <output>
USAGE:
    basic --output <output> --speed <speed>
For more information try --help
$ ./basic --help
basic 0.3.0
Guillaume Pinot <texitoi@texitoi.eu>, others
A basic example
USAGE:
    basic [FLAGS] [OPTIONS] --output <output> [--] [file]...
FLAGS:
    -d, --debug      Activate debug mode
    -h, --help       Prints help information
    -V, --version    Prints version information
    -v, --verbose    Verbose mode (-v, -vv, -vvv, etc.)
OPTIONS:
    -l, --level <level>...     admin_level to consider
    -c, --nb-cars <nb-cars>    Number of cars
    -o, --output <output>      Output file
    -s, --speed <speed>        Set speed [default: 42]
ARGS:
    <file>...    Files to process
$ ./basic -o foo.txt
Opt {
    debug: false,
    verbose: 0,
    speed: 42.0,
    output: "foo.txt",
    nb_cars: None,
    level: [],
    files: [],
}
$ ./basic -o foo.txt -dvvvs 1337 -l alice -l bob --nb-cars 4 bar.txt baz.txt
Opt {
    debug: true,
    verbose: 3,
    speed: 1337.0,
    output: "foo.txt",
    nb_cars: Some(
        4,
    ),
    level: [
        "alice",
        "bob",
    ],
    files: [
        "bar.txt",
        "baz.txt",
    ],
}