structopt 0.3.26

Parse command line argument by defining a struct.


Build status unsafe forbidden

Parse command line arguments by defining a struct. It combines clap with custom derive.


As clap v3 is now out, and the structopt features are integrated into (almost as-is), structopt is now in maintenance mode: no new feature will be added.

Bugs will be fixed, and documentation improvements will be accepted.


Find it on You can also check the examples and the changelog.


Add structopt to your dependencies of your Cargo.toml:

structopt = "0.3"

And then, in your rust file:

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);

Using this example:

$ ./basic
error: The following required arguments were not provided:
    --output <output>

    basic --output <output> --speed <speed>

For more information try --help
$ ./basic --help
basic 0.3.0
Guillaume Pinot <>, others
A basic example

    basic [FLAGS] [OPTIONS] --output <output> [--] [file]...

    -d, --debug      Activate debug mode
    -h, --help       Prints help information
    -V, --version    Prints version information
    -v, --verbose    Verbose mode (-v, -vv, -vvv, etc.)

    -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]

    <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(
    level: [
    files: [

StructOpt rustc version policy

  • Minimum rustc version modification must be specified in the changelog and in the travis configuration.
  • Contributors can increment minimum rustc version without any justification if the new version is required by the latest version of one of StructOpt's dependencies (cargo update will not fail on StructOpt).
  • Contributors can increment minimum rustc version if the library user experience is improved.


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.