Add not builtin command - tail

.gitignore

@@ -1,2 +1,3 @@
 /target
+/bin
 Cargo.lock

src/tail.rs

@@ -0,0 +1,42 @@
+use std::env;
+use std::fs::File;
+use std::path::Path;
+use std::io::BufReader;
+use std::io::prelude::*;
+
+fn main() -> std::io::Result<()>  {
+    let args: Vec<String> = env::args().collect();
+    let mut num_of_lines: i32 = 10;
+    for arg in 1..args.len() {
+        match args[arg].as_str() {
+            "--help" => {
+                println!("Usage: tail [OPTIONS] FILE");
+                println!("Output the last part of files");
+            },
+            "-n" => {
+                num_of_lines = args[arg+1].parse::<i32>().unwrap();
+            }
+            arg => {
+                if Path::new(arg).exists() {
+                    get_line_at(Path::new(arg), num_of_lines);
+                }
+            }
+        }
+    }
+    Ok(())
+}
+
+fn get_line_at(path: &Path, line_num: i32) -> Result<(),()> {
+    let file = File::open(path).expect("File not found or cannot be opened");
+    let content = BufReader::new(&file);
+    let lines = content.lines();
+    let mut lines_vec: Vec<String> = Vec::new();
+    for line in lines {
+        lines_vec.push(line.unwrap());
+    }
+    let line_num = lines_vec.len() - (line_num as usize);
+    for line in line_num..lines_vec.len() {
+        println!("{}", lines_vec[line]);
+    }
+    Ok(())
+}