Use when building CLI tools. Keywords: CLI, command line, terminal, clap, structopt, argument parsing, subcommand, interactive, TUI, ratatui, crossterm, indicatif, progress bar, colored output, shell completion, config file, environment variable, 命令行, 终端应用, 参数解析
| Domain Rule | Design Constraint | Rust Implication |
|---|---|---|
| User ergonomics | Clear help, errors | clap derive macros |
| Config precedence | CLI > env > file | Layered config loading |
| Exit codes | Non-zero on error | Proper Result handling |
| Stdout/stderr | Data vs errors | eprintln! for errors |
| Interruptible | Handle Ctrl+C | Signal handling |
| Purpose | Crate |
|---|---|
| Argument parsing | clap |
| Interactive prompts | dialoguer |
| Progress bars | indicatif |
| Colored output | colored |
| Terminal UI | ratatui |
| Terminal control | crossterm |
| Console utilities | console |
| Pattern | Purpose | Implementation |
|---|---|---|
| Args struct | Type-safe args | #[derive(Parser)] |
| Subcommands | Command hierarchy | #[derive(Subcommand)] |
| Config layers | Override precedence | CLI > env > file |
| Progress | User feedback | ProgressBar::new(len) |
use clap::{Parser, Subcommand};
#[derive(Parser)]
#[command(name = "myapp", about = "My CLI tool")]
struct Cli {
/// Enable verbose output
#[arg(short, long)]
verbose: bool,
#[command(subcommand)]
command: Commands,
}
#[derive(Subcommand)]
enum Commands {
/// Initialize a new project
Init { name: String },
/// Run the application
Run {
#[arg(short, long)]
port: Option<u16>,
},
}
fn main() -> anyhow::Result<()> {
let cli = Cli::parse();
match cli.command {
Commands::Init { name } => init_project(&name)?,
Commands::Run { port } => run_server(port.unwrap_or(8080))?,
}
Ok(())
}
| Mistake | Domain Violation | Fix |
|---|---|---|
| Errors to stdout | Breaks piping | eprintln! |
| No help text | Poor UX | #[arg(help = "...")] |
| Panic on error | Bad exit code | Result + proper handling |
| No progress for long ops | User uncertainty | indicatif |