Read a file line by line

use std::fs::File;
use std::io::{self, BufRead, BufReader};
use std::path::Path;

fn read_lines<P>(path: P) -> io::Result<Vec<String>>
where
    P: AsRef<Path>,
{
    let file = File::open(path)?;
    let reader = BufReader::new(file);
    reader.lines().collect()
}

fn main() -> io::Result<()> {
    for (n, line) in read_lines("input.txt")?.iter().enumerate() {
        println!("{:>4}: {}", n + 1, line);
    }
    Ok(())
}