Subcommands in Rust

One binary, several verbs: an enum of subcommands, each with its own args.

use clap::{Parser, Subcommand};

#[derive(Parser)]
struct Cli {
    #[arg(long, global = true)]
    quiet: bool,

    #[command(subcommand)]
    command: Command,
}

#[derive(Subcommand)]
enum Command {
    /// Play a tour step
    Play { lang: String, idx: u32 },
    /// Show your statistics
    Stats {
        #[arg(long, default_value = "week")]
        window: String,
    },
}

fn main() {
    let cli = Cli::parse();
    match cli.command {
        Command::Play { lang, idx } => println!("playing {lang} step {idx}"),
        Command::Stats { window } => println!("stats for the {window}"),
    }
    if !cli.quiet {
        println!("done");
    }
}

How it works

1. #[derive(Subcommand)] on an enum gives one variant per verb.
2. The parent struct holds the global flags.
3. Matching on the enum dispatches the work.

Keywords and builtins used here

• Cli
• Command
• String
• bool
• enum
• fn
• if
• let
• main
• match
• struct
• u32
• use

The run, in numbers

Lines

32

Characters to type

563

Tokens

133

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 80 seconds.

Type this snippet

Step 4 of 5 in Arguments, step 4 of 12 in CLI tools & HTTP clients.

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Subcommands in other languages

• Python