diff --git a/2022/day4/Cargo.lock b/2022/day4/Cargo.lock
new file mode 100644
index 0000000..e92c02c
--- /dev/null
+++ b/2022/day4/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day4"
+version = "0.1.0"
diff --git a/2022/day4/Cargo.toml b/2022/day4/Cargo.toml
new file mode 100644
index 0000000..8842130
--- /dev/null
+++ b/2022/day4/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day4"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/2022/aoc2022/data/day4-input.txt b/2022/day4/input.txt
similarity index 100%
rename from 2022/aoc2022/data/day4-input.txt
rename to 2022/day4/input.txt
diff --git a/2022/aoc2022/src/day4.rs b/2022/day4/src/main.rs
similarity index 89%
rename from 2022/aoc2022/src/day4.rs
rename to 2022/day4/src/main.rs
index 80eef70..0b4cb35 100644
--- a/2022/aoc2022/src/day4.rs
+++ b/2022/day4/src/main.rs
@@ -1,8 +1,7 @@
-use std::io::Result;
+use std::env;
+use std::fs;
 use std::ops::RangeInclusive;
 
-use crate::file::line_reader_for_file;
-
 #[derive(PartialEq, PartialOrd)]
 struct RangeString(String);
 
@@ -55,10 +54,15 @@ impl Assignment {
     }
 }
 
-pub fn main(filename: &str) -> Result<()> {
-    let assignment_counts: (u32, u32, u32) = line_reader_for_file(filename)?
+pub fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    let filename = args.get(1).expect("Missing filename argument");
+
+    let file_contents = fs::read_to_string(&filename).expect("Unable to read file");
+
+    let assignment_counts: (u32, u32, u32) = file_contents.lines()
         .map(|line| -> Assignment {
-            let line = line.unwrap();
             let mut elves = line.split(",").map(|s| RangeString::from(s));
             let assignment = Assignment::from_left_and_right_specifier(
                 elves.next().unwrap(),
@@ -89,6 +93,4 @@ pub fn main(filename: &str) -> Result<()> {
         "Part 2: number of assignments with ranges at least partially overlapping: {}",
         assignment_counts.2
     );
-
-    Ok(())
 }