この本を使用して勉強しています。

本日はコマンドラインから引数を取得する処理。

Clapを使用する方法が紹介されていたが、サンプルが古いのでそのまま使えず、結局公式のサンプルコードを見るハメに。

https://docs.rs/clap/latest/clap/

[dependencies]
clap = { version = "3.1.6", features = ["derive"] }

use clap::Parser;

#[derive(Parser, Debug)]
#[clap(
    name = "My RPM program",
    version = "1.0.0",
    author = "Your name",
    about = "Super awesome sample RPM calculator"
)]
struct Opts {
    #[clap(short, long)]
    verbose: bool,

    #[clap(name = "FILE")]
    formula_file: Option<String>,
}

fn main() {
    let opts = Opts::parse();
    match opts.formula_file {
        Some(file) => println!("File specified: {}", file),
        None => println!("No file specified."),
    }
    println!("Is verbosity specified?: {}", opts.verbose);
}

Clapを適用するには、Cargo.tomlの[dependencies]に一文を追加するだけでOK。

また、テキストではclap::Clapと書かれていたが、最新版ではclap::Parserが正解らしい。

置き換えたのはそれくらいか？

~/rust/samplecli$ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli`
No file specified.
Is verbosity specified?: false

~/rust/samplecli$ cargo run -- input.txt
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli input.txt`
File specified: input.txt
Is verbosity specified?: false

~/rust/samplecli$ cargo run -- -v input.txt
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli -v input.txt`
File specified: input.txt
Is verbosity specified?: true

~/rust/samplecli$ cargo run -- -h
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli -h`
My RPM program 1.0.0
Your name
Super awesome sample RPM calculator

USAGE:
    samplecli [OPTIONS] [FILE]

ARGS:
    <FILE>    

OPTIONS:
    -h, --help       Print help information
    -v, --verbose    
    -V, --version    Print version information

~/rust/samplecli$ cargo run -- -d
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli -d`
error: Found argument '-d' which wasn't expected, or isn't valid in this context

        If you tried to supply `-d` as a value rather than a flag, use `-- -d`

USAGE:
    samplecli [OPTIONS] [FILE]

For more information try --help

~/rust/samplecli$ cargo run -- input.txt input2.txt
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/samplecli input.txt input2.txt`
error: Found argument 'input2.txt' which wasn't expected, or isn't valid in this context

USAGE:
    samplecli [OPTIONS] [FILE]

For more information try --help