Up to 12.4

.gitignore

@@ -0,0 +1 @@
+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "minigrep"
+version = "0.1.0"

poem.txt

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+I'm nobody! Who are you?
+Are you nobody, too?
+Then there's a pair of us - don't tell!
+They'd banish us, you know.
+
+How dreary to be somebody!
+How public, like a frog
+To tell your name the livelong day
+To an admiring bog!

src/lib.rs

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+use std::error::Error;
+use std::fs;
+
+pub struct Config {
+    pub query: String,
+    pub file_path: String,
+}
+
+impl Config {
+    pub fn build(args: &[String]) -> Result<Config, &'static str> {
+        if args.len() < 3 {
+            return Err("not enough arguments");
+        }
+
+        let query = args[1].clone();
+        let file_path = args[2].clone();
+
+        Ok(Config { query, file_path })
+    }
+}
+
+pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
+    let contents = fs::read_to_string(config.file_path)?;
+
+    println!("With text:\n{}", contents);
+
+    Ok(())
+}

src/main.rs

@@ -1,3 +1,21 @@
+use std::env;
+use std::process;
+
+use minigrep::Config;
+
 fn main() {
-    println!("Hello, world!");
+    let args: Vec<String> = env::args().collect();
-}
+
+    let config = Config::build(&args).unwrap_or_else(|err| {
+        println!("Problem parsing arguments: {err}");
+        process::exit(1);
+    });
+
+    println!("Searching for {}", config.query);
+    println!("In file {}", config.file_path);
+
+    if let Err(e) = minigrep::run(config) {
+        println!("Application error: {e}");
+        process::exit(1);
+    }
+}