5 files changed, 115 insertions, 0 deletions
diff --git a/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.lock b/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.lock
new file mode 100644
index 000000000..88bf82d16
--- /dev/null
+++ b/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.lock
@@ -0,0 +1,6 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "minigrep"
+version = "0.1.0"
+
diff --git a/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.toml b/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.toml
new file mode 100644
index 000000000..64c2a3f52
--- /dev/null
+++ b/src/doc/book/listings/ch12-an-io-project/listing-12-20/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "minigrep"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/src/doc/book/listings/ch12-an-io-project/listing-12-20/poem.txt b/src/doc/book/listings/ch12-an-io-project/listing-12-20/poem.txt
new file mode 100644
index 000000000..870752731
--- /dev/null
+++ b/src/doc/book/listings/ch12-an-io-project/listing-12-20/poem.txt
@@ -0,0 +1,9 @@
+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!
diff --git a/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/lib.rs b/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/lib.rs
new file mode 100644
index 000000000..a757f7f55
--- /dev/null
+++ b/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/lib.rs
@@ -0,0 +1,76 @@
+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)?;
+
+    for line in search(&config.query, &contents) {
+        println!("{line}");
+    }
+
+    Ok(())
+}
+
+pub fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
+    let mut results = Vec::new();
+
+    for line in contents.lines() {
+        if line.contains(query) {
+            results.push(line);
+        }
+    }
+
+    results
+}
+
+// ANCHOR: here
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn case_sensitive() {
+        let query = "duct";
+        let contents = "\
+Rust:
+safe, fast, productive.
+Pick three.
+Duct tape.";
+
+        assert_eq!(vec!["safe, fast, productive."], search(query, contents));
+    }
+
+    #[test]
+    fn case_insensitive() {
+        let query = "rUsT";
+        let contents = "\
+Rust:
+safe, fast, productive.
+Pick three.
+Trust me.";
+
+        assert_eq!(
+            vec!["Rust:", "Trust me."],
+            search_case_insensitive(query, contents)
+        );
+    }
+}
+// ANCHOR_END: here
diff --git a/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/main.rs b/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/main.rs
new file mode 100644
index 000000000..a4f8a7411
--- /dev/null
+++ b/src/doc/book/listings/ch12-an-io-project/listing-12-20/src/main.rs
@@ -0,0 +1,18 @@
+use std::env;
+use std::process;
+
+use minigrep::Config;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    let config = Config::build(&args).unwrap_or_else(|err| {
+        println!("Problem parsing arguments: {err}");
+        process::exit(1);
+    });
+
+    if let Err(e) = minigrep::run(config) {
+        println!("Application error: {e}");
+        process::exit(1);
+    }
+}