cat 実装

Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+clap = { version = "4.5.4", features = ["derive"] }

Makefile

@@ -0,0 +1,11 @@
+.PHONY: all
+all:
+	cargo build
+
+.PHONY: fmt
+fmt:
+	cargo fmt
+
+.PHONY: lint
+lint:
+	cargo clippy

README.md

@@ -2,3 +2,37 @@
 
 zztkm tool box.
 
+Rust の練習がてら Linux コマンドを再実装したり、自分がほしいコマンドを実装したりしています。
+
+## Usage
+
+```bash
+# 引数がない場合は標準入力から読み取ります
+$ cat README.md | cargo run -- cat                                                                                   at 01:46:25
+    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.02s
+     Running `target/debug/ztb cat`
+# ztb
+
+zztkm tool box.
+
+# 引数ありの場合
+$ cargo run -- cat README.md Makefile                                                                                at 01:48:46
+    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.01s
+     Running `target/debug/ztb cat README.md Makefile`
+# ztb
+
+zztkm tool box.
+
+.PHONY: all
+all:
+	cargo build
+
+.PHONY: fmt
+fmt:
+	cargo fmt
+
+.PHONY: lint
+lint:
+	cargo clippy
+```
+

src/main.rs

@@ -1,3 +1,50 @@
+use clap::{Parser, Subcommand};
+use std::io::{Read, Write};
+
+#[derive(Parser)]
+struct Cli {
+    #[command(subcommand)]
+    command: Commands,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    Cat { files: Option<Vec<String>> },
+}
+
 fn main() {
-    println!("Hello, world!");
+    let cli = Cli::parse();
+
+    match &cli.command {
+        Commands::Cat { files } => {
+            if let Some(files) = files {
+                // stdout のロックを取得
+                let stdout = std::io::stdout();
+                let mut stdout = stdout.lock();
+
+                // files を入力順に stdout に出力する
+                // 最後のファイルは改行をしない
+                let mut iter = files.iter().peekable();
+                while let Some(file) = iter.next() {
+                    let content = std::fs::read_to_string(file).unwrap();
+                    if iter.peek().is_none() {
+                        write!(&mut stdout, "{}", content).unwrap();
+                    } else {
+                        writeln!(&mut stdout, "{}", content).unwrap();
+                    }
+                }
+            } else {
+                // files の指定がない場合は標準入力から読み取る
+                let mut buffer = String::new();
+                let stdin = std::io::stdin();
+                let mut stdin = stdin.lock();
+                stdin.read_to_string(&mut buffer).unwrap();
+
+                // 標準出力に書き込む
+                let stdout = std::io::stdout();
+                let mut stdout = stdout.lock();
+                write!(&mut stdout, "{}", buffer).unwrap();
+            }
+        }
+    }
 }