diff --git a/minigrep/poem.txt b/minigrep/poem.txt
new file mode 100644
index 0000000..b0fc12f
--- /dev/null
+++ b/minigrep/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!
\ No newline at end of file
diff --git a/minigrep/src/lib.rs b/minigrep/src/lib.rs
new file mode 100644
index 0000000..05bf6f5
--- /dev/null
+++ b/minigrep/src/lib.rs
@@ -0,0 +1,129 @@
+use std::error::Error;
+use std::fs;
+use std::env;
+
+pub struct Config {
+    pub query: String,
+    pub filename: String,
+    pub case_sensitive: bool,
+}
+
+impl Config {
+    pub fn new(args: &[String]) -> Result<Config, &'static str> {
+        if args.len() < 3 {
+            return Err("not enough arguments");
+        }
+        let query = args[1].clone();
+        let filename = args[2].clone();
+
+        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
+    
+        Ok(Config { query, filename, case_sensitive })
+    }
+}
+
+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
+}
+
+fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
+    let mut results = Vec::new();
+    let query = query.to_lowercase();
+
+    for line in contents.lines() {
+        if line.to_lowercase().contains(&query) {
+            results.push(line);
+        }
+    }
+
+    results
+}
+
+pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
+    let contents = fs::read_to_string(config.filename)?;
+
+    let results = if config.case_sensitive {
+        search(&config.query, &contents)
+    } else {
+        search_case_insensitive(&config.query, &contents)
+    };
+
+    for line in results {
+        println!("{}", line);
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn search_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)
+        );
+    }
+
+    #[test]
+    fn run_valid_file() {
+        assert!(run(Config {
+            query: String::from("test"),
+            filename: String::from("poem.txt"),
+        }).is_ok());
+    }
+
+    #[test]
+    fn run_invalid_file() {
+        assert!(run(Config {
+            query: String::from("test"),
+            filename: String::from("134857320592.txt"),
+        }).is_err());
+    }
+
+    #[test]
+    fn config_new_valid() {
+        assert!(Config::new(
+            &vec![
+                String::from("binaryname"),
+                String::from("query"),
+                String::from("filename")]).is_ok());
+    }
+
+    #[test]
+    fn config_new_invalid() {
+        assert!(Config::new(
+            &vec![
+                String::from("only two"),
+                String::from("arguments")]).is_err());
+    }
+}
\ No newline at end of file
diff --git a/minigrep/src/main.rs b/minigrep/src/main.rs
index 8733eaf..d52c4f1 100644
--- a/minigrep/src/main.rs
+++ b/minigrep/src/main.rs
@@ -1,6 +1,18 @@
 use std::env;
+use std::process;
+
+use minigrep::Config;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
-    println!("{:?}", args);
+
+    let config = Config::new(&args).unwrap_or_else(|err| {
+        eprintln!("Problem parsing arguments: {}", err);
+        process::exit(1);
+    });
+
+    if let Err(e) = minigrep::run(config) {
+        eprintln!("Application error: {}", e);
+        process::exit(1);
+    }
 }
\ No newline at end of file