use std::fs::File;
use std::io::BufRead;
use std::io::BufReader;
use std::io::Error;
use std::path::Path;

fn main() {
    let path = Path::new("file.txt");
    let line_num = 7usize;
    let line = get_line_at(&path, line_num - 1);
    println!("{}", line.unwrap());
}

fn get_line_at(path: &Path, line_num: usize) -> Result<String, Error> {
    let file = File::open(path).expect("File not found or cannot be opened");
    let content = BufReader::new(&file);
    let mut lines = content.lines();
    lines.nth(line_num).expect("No line found at that position")
}