add get nth line function

src/userlib.rs

@@ -216,6 +216,15 @@ impl UserDBValidation for UserDBLocal {
     }
 }
 
+fn get_nth_line(path: Option<&PathBuf>, n: u32) -> String {
+    let lines = file_to_string(path);
+    let line = lines.lines().nth(n as usize);
+    match line {
+        Some(line) => line.to_owned(),
+        None => "".to_owned(),
+    }
+}
+
 /// Parse a file to a string
 fn file_to_string(path: Option<&PathBuf>) -> String {
     let file = File::open(path.expect("Path cannot be None".into()))