项目实战：命令行工具

[dependencies]
clap = { version = "4", features = ["derive"] }

use clap::Parser;
 
#[derive(Parser)]
#[command(name = "mywc", about = "简易 wc 工具")]
struct Cli {
    /// 要统计的文件路径
    #[arg(required = true)]
    path: String,
 
    /// 是否统计字符数
    #[arg(short, long)]
    chars: bool,
}
 
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let cli = Cli::parse();
    let content = std::fs::read_to_string(&cli.path)?;
 
    let lines = content.lines().count();
    let words = content.split_whitespace().count();
    let chars = content.chars().count();
 
    println!("行数: {}", lines);
    println!("词数: {}", words);
    if cli.chars {
        println!("字符数: {}", chars);
    }
    Ok(())
}

#[derive(clap::Subcommand)]
enum Command {
    /// 统计文件
    Count { path: String },
    /// 显示版本信息
    Version,
}
 
#[derive(Parser)]
struct Cli {
    #[command(subcommand)]
    command: Command,
}

cargo run -- ./README.md --chars
# 行数: 120
# 词数: 800
# 字符数: 5400