#commander #git


This crate is used by commander-rust only. Please don't use it!

5 stable releases

1.2.0 Apr 30, 2019
1.1.4 Apr 30, 2019
1.1.3 Apr 25, 2019
1.1.2 Apr 24, 2019
1.0.0 Apr 21, 2019

21 downloads per month
Used in commander-rust

MIT license

824 lines


See example/glance.rs for more details.

#[option(--https, "use https instead of http")]
#[sub_command(connect <address>, "connect to the address")]
fn connect(address: Option<Address>, opts: Opts, global_opts: GlobalOpts) {
    /* .. */

#[sub_command(disconnect <address>, "disconnect the connection")]
fn disconnect(address: Option<Address>) {
    /* .. */

#[option(--proxy <proxy_address>, "use proxy to connect")]
#[command(net, "network tool")]
fn net() { /* .. */}

fn main() {
    execute!(net, [connect, disconnect]);


The current master branch will no longer be supported. And the branch pre-alpha will be the master branch once it's stable.


The current commander_rust in crate.io is no longer supported. Before it becomes stable, github will be used as distribution source. Add it to your dependencies.

git = "https://github.com/MSDimos/commander-rust/"
branch = "pre-alpha"

# or
commander_rust = { git = "https://github.com/MSDimos/commander-rust/", branch = "pre-alpha" }


As I think, developers should devote more time to the realization of functions instead of leaning how to use command line interface (CLI). So a crate of CLI should be easy to use. Specifically, it should have the following advantages:

  • Firstly, it should have less APIs.
  • Secondly, it should be intuitive enough to use. What u see is what u get.
  • Thirdly, it should make full use of the advantages of programming language.

Inspired by Rocket and commander.js, the crate is born.

Design concept

A CLI program consists of CommandSubCommandOptions and Argument

Options is exactly Option, but Rust has used Option already, so I use it as replacement.

The relationships between them are:

  1. One CLI has ONLY ONE Command.
  2. One Command has ZERO or MORE SubCommands.
  3. Command and SubCommand have ZERO or MORE Options.
  4. SubCommand and Options can accept ZERO or MORE Argument.

For instance, see examples below:

command <require_argument> <optional_argument> --option
command sub_command <require_argument> <optional_argument> --option

attribute macros


Defining options using #[option]. Syntax shows below:

#[option([-s], --long-name <arg1> [arg2], "description about this option")]

Note, options of command are global options, it means sub-command can access them.

fn test() {
    // input
    // paht/of/example test --global-option

fn test_sub(opts: Opts) {
    // input:
    // path/of/example test test_sub --global-option --local-option

Options without arguments are also called flag or switch (Ha, not Nintendo Switch).

restriction of #[option]

All options should be defined above command or sub_command.
All options defined below command or sub_command will be ignored. See example below:

// valid
#[option(--display, "display something")]
#[option(-v, --version, "display version")]
#[sub_command(cmd_name, "this is a sub_command")]
fn sub_cmd_fn() {} 

// these below are all invalid

#[sub_command(cmd_name, "this is a sub_command")]
#[option(--display, "display something")]
#[option(-v, --version, "display version")]
fn sub_cmd_fn1() {} 

#[option(--display, "display something")]
#[sub_command(cmd_name, "this is a sub_command")]
#[option(-v, --version, "display version")]
fn sub_cmd_fn2() {} 


fn test() {}

// is equal to
#[option(-v, --version, "print version information")]
#[option(-h, --help, "print help information")]
fn test() {}

restriction of #[default_options]

Once you use #[default_options], other options of this sub_command or command can't use short names -v -h or long names --version --help. See example below:

// Error, `-v` is reserved keyword which is used by `#[default_options]`
#[option(-v, --verbose, "display verbose information")]
// Error, `--help` is reserved keyword which is used by `#[default_options]`
#[option(--help, "need help")]
fn test() {}

#[command] and #[sub_command]

They have the similar syntax which are shown below:

// sub_command
#[sub_command(sub_cmd_name <arg1> [args], "this is a sub-command")]

// command without app version
// in this case, environment variable `CARGO_PKG_VERSION` (i.e., std::env!("CARGO_PKG_VERSION")) will be used as app version
#[command(cmd_name <arg1> [args], "this is a sub-command")]
// command with app version
#[command("0.0.1-pre-alpha", cmd_name <arg1> [args], "this is a sub-command")]

restriction of #[command] or #[sub_command]

#[command] is only, but #[sub_command] s are not.

procedural macros


Run the cli app. If you don't call it, the cli app will not run.

Syntax is shown as example below:

// Note, these `*_fn_name*` are names of function instead of names of `sub_command` or `command`
execute!(command_fn_name, [sub_command_fn_name1, sub_command_fn_name2, ...])
// if no sub_command needed, provide a `[]`
execute!(command_fn_name, [])

Note: Because of restrictions of Rust, if you want to used procedural macro, you should add attribute #![feature(proc_macro_hygiene)]. See this issuefor more details.

restriction of execute!()

Because of the internal mechanism, all functions which are used in execute!() should be at the same level of modules. It means the example below will raise error:

mod child_mod {
    #[sub_command(test_sub, "test1")]
	pub fn test1() {}

#[command(test_cmd, "test2")]
fn test2() {}

use child_mod::test1;

fn main() {
     // Error, cannot find function `_commander_rust_prefix_test1_commander_rust_suffix_` in this scope
    execute!(test2, [test1]);

Extract arguments

types of arguments

There are four types of arguments. Listed below:

  • required single argument:<arg>
  • required multiply arguments: <..args> or <...args>
  • optional single argument:[arg]
  • optional multiply arguments: [..args] or [...args]

In fact, required multiply arguments is equal to optional multiply arguments.

Note: there are several restrictions:

  1. All optional arguments should be after all required arguments.
// valid
#[option(test <a> <b> [c] [d])]
// invalid
#[option(test <a> [b] <c> [d])]
  1. There can be only one multiply argument, and it can only be used as the last parameter.
// valid
#[otpion(test <a> <..b>)]
// invalid
#[option(test <..a> <b>)]

extract named arguments

See example below.

#[option(--user-name <name>, "login with username")]
#[option(--passwd <passwd>, "login with passwd")]
// all named arguments (e.g. here, <url>) should be used in function signature
#[command(login <url>, "login")]
fn login_fn(url: String) {}

is named argument of option --user-name, <passwd> is named argument of option --passwd. And url is a named argument of command login.

Of course, you can customize the type of named arguments. Any type that implement the trait FromArg or FromArgs can be used as type of named arguments.

What's different between FromArg and FromArgs?

  • FromArg is used for type of named arguments which are single arguments (e.g., <arg> or [arg]).
  • FromArgs is used for type of named arguments which are multiply arguments (e.g., <..arg> or [..arg]).

There are several types that implement the trait FromArg:

  • String and &str
  • Option<T: FromArg>
  • Result<T: FromArg, T::Error>
  • i8 i16 i32 i64 i128 u8 u16 u32 u64 u128
  • &Arg
  • Path and PathBuf

There are several types that implement the trait FromArgs:

  • String
  • Vec<T: FromArg> (not T: FromArgs)
  • Option<T: FromArgs>
  • Result<T: FromArgs, T::Error>
  • &Args

How to implement the two traits above? Let me show u an example.

Now, I define an command with an argument.

#[command(download <pkg>, "download an package")]
fn connect(pkg: Pkg) {
    match down_load_pkg(&pkg.name, &pkg.version) {
        Ok(_) => println!("success"),
        Err(e) => eprintln!("{}", e),

I don't want to use String, but I use a type named Pkg. I want to decode user's input which is formatted like react=16.13.1. Now, let's define the struct Pkg.

struct Version(u8, u8, u8);

struct Pkg {
    name: String,
    version: Version,

Now, the highlight is coming. Let's implement the trait FromArg, then we can use it.

impl<'a> FromArg<'a> for Pkg {
    type Error = ();

    // see document for more details about `Arg` and `Args`
    fn from_arg(arg: &'a Arg) -> Result<Self, Self::Error> {
        let splits: Vec<&str> = arg.split('=').collect();

        if splits.len() != 2 {
        } else {
            let name = splits[0];
            let vers: Vec<&str> = splits[1].split('.').collect();

            if vers.len() != 3 {
            } else {
                let mut vs = [0, 0, 0];

                for (idx, ver) in vers.into_iter().enumerate() {
                    if let Ok(v) = ver.parse::<u8>() {
                        vs[idx] = v;
                    } else {
                        return Err(());

                Ok(Pkg {
                    name: name.to_string(),
                    version: Version(vs[0], vs[1], vs[2]),

Ha, it's done. Now you can use the cli app like:

$ /path/of/download react=16.13.1

But there are some bugs here. Look the line 8 line 14 line 22 in the code above. It returned the Err. It means sometimes it will crash. Try to input like this:

// Error, parse failed, can't parse input `react=16` as type `Pkg`
$ /path/of/download react

How to catch errors and handle them yourself ? It's easy, do u remember that there are several types which implement the trait FromArg? Option<T: FromArg> and Result<T: FromArg, T::Error> are two of them. So, change the signature of function:

#[command(download <pkg>, "download an package")]
// Or pkg: Result<Pkg, ()>, both are okay
fn connect(pkg: Option<Pkg>) {
	if let Some(pkg) = pkg {
        match down_load_pkg(&pkg.name, &pkg.version) {
            Ok(_) => println!("success"),
            Err(e) => eprintln!("{}", e),
    } else {
        // if you want to do something, do it.
        eprintln!("can't parse package.");

Now, If you input:

// customize error, can't parse package.
$ /path/of/download react

If you want to download multiply packages like:

$ /path/of/download react=16.13.1 react-redux=7.2.0

Change signature of function download like:

#[command(download <pkg>, "download an package")]
// Or pkgs: Vec<Result<Pkg, ()>>, both are okay
fn connect(pkgs: Vec<Option<Pkg>>) {
	if pkgs.is_empty() {
        eprintln!("no packages offered.");
    } else {
        for pkg in pkgs.into_iter() {
            if let Some(pkg) = pkg {
                match down_load_pkg(&pkg.name, &pkg.version) {
                    Ok(_) => printlnr!("success"),
                    Err(e) => eprintln!("{}", e),
            } else {
                // if you want to do something, do it.
                eprintln!("can't parse package.");

Extract options

Opts and GlobalOpts

I offer u two types to get options. One is Opts, the other one is GlobalOpts. By names, you should be able to know the difference between them.

#[option(-f, --force, "force to install even if this package has already installed")]
#[option(-g, --global, "install as a global package")]
#[sub_command(install <pkg>, "install a package")]
fn install_fn(pkg: Result<Pkg, ()>, opts: Opts, global_opts: GlobalOpts) {
   	if opts.contains_key("force") {
        // do something here
    if global_opts.contains_key("verbose") {
        // do something here

extract arguments of options

Like arguments of command, arguments of options have implemented the trait FromArg or FromArgs. See example below:

#[option(--fruit <fruit>)]
fn eat(opts: Opts) {
    // try to get option
    if let Some(Mixed::Single(fruit)) = opts.get("fruit") {
        // "apple" is default value
        let fruit = String::from_arg(fruit).unwrap_or("apple".to_string());
        println!("I eat a(n) {}", fruit);

Code above used type Mixed. Why it? See example below:

#[option(--test <a> <b> <..c>)]

As you can see, <a> and <b> are both sigle arguments. But <..c> is multiply argument.

If you want to get named arguments of --test by using api get, it will return value of type Result<Mixed, ()>.

In this case, for single arguments, Mixed is Mixed::Signle which only contains one input value. For multiply arguments, Mixed is Mixed::Multiply which contains more input value.

You can see document or source code for more details.

advanced usage of options

Repeat: All types of named arguments should implement the trait FromArg(for single argument) or FromArgs(for multiply arguments).

If you offer non-named arguments, the types of them should implement the trait FromApp.

See document for more details about struct App.

Opts and GlobalOpts have already implemented the trait FromApp. There are several types that implement the trait FromApp.

  • Application and &Application(alias App and &App)
  • &Command
  • Result<T: FromApp, T::Error>
  • Option<T: FromApp>

See document for more details about struct Command. It contains all information about you cli app.

If you want to show help or version information, there are three apis of Command you can use:

  1. cmd.println() -- print help information of command
  2. cmd.println_sub("sub_name") -- print help information of the specified sub-command
  3. cmd.println_version() -- print version information
fn npms_fn(cmd: &Command) {

How to implement the trait FromApp. See example below:

enum DangerousThing {

// by implementing the trait `FromApp`, you can do many multiple custom options types
// e.g. here, mutually exclusive options
struct MutexThing(DangerousThing);

impl<'a> FromApp<'a> for MutexThing {
    type Error = String;

    fn from_app(app: &'a Application) -> Result<Self, Self::Error> {
        // You can use `<T as FromApp>::from_app(app)` to convert app to `T`
        if let Ok(opts) = GlobalOpts::from_app(app) {
            if opts.contains_key("cephalosporin") && opts.contains_key("drink-wine") {
                Err(String::from("DANGER!!! DO NOT DO IT! DO NOT take cephalosporin while drinking wine!"))
            } else if opts.contains_key("cephalosporin") {
            } else {
        } else {

// WARN: DO NOT take cephalosporin while drinking wine! It's fatal behavior!!!!!!!!
#[option(--cephalosporin, "take cephalosporin")]
#[option(--drink-wine, "drink wine")]
#[command("0.0.1-fruits-eater", eat <food>, "eat food")]
// Here, do u see it?
// mutex_thing is not named argument, so it should implement the trait `FromApp`.
fn eat_fn(food: String, mutex_thing: Result<MutexThing, String>) {
    match food.as_str() {
        "apple" | "banana" | "pear" | "watermelon" | "orange" => println!("I eat a(n) {}, it's delicious!", food),
        _ => println!("I dislike {}", food),

    match mutex_thing {
        Ok(MutexThing(DangerousThing::Cephalosporin)) => println!("DO NOT drink wine recently!"),
        Ok(MutexThing(DangerousThing::Wine)) => println!("DO NOT take cephalosporin recently!"),
        Ok(MutexThing(DangerousThing::None)) => println!("I want to eat more!"),
        Err(note) => println!("{}", note),


  1. There are three traits you may will use:
Name description
FromArg single named arguments should implement it, e.g., <arg> or [arg]
FromArgs multiply named arguments should implement it, e.g., <..args> or [..args]
FromApp non-named arguments of function signature(if it exists) should implement it.
  1. You can use Opts and GlobalOpts to get options.

  2. You can use &Command to print help and version information by yourself.

  3. Run cli app by calling macro execute!().


You can check examples in folder examples of this crate for full usage of commander_rust.


Because of something that happened to me, I stopped maintaining the previous version of this project for a long time.

After all that, I have time to maintain the project. I am sorry for those people who opened issues, because of refactoring of the project, I can't and needn't to respond them any more. Now, starting from scratch, any useful contribution is welcome.

If you find bug and fix it, please create an Merge Request.

If you have a good idea and implement it, please create an Merge Request.

If you have any questions, please open an issue.

TODO list

  • i18n support?

  • sub-sub*n-sub-commands support?

  • cross modules support?