use std::io::{self, stdout, Write};
use std::env;
use std::process::Command;
use std::path::Path;

fn main() {
    loop {
    print!("$ ");
    io::stdout().flush();
    
    let mut input = String::new();
    io::stdin().read_line(&mut input).unwrap();
    
    let mut parts = input.trim().split_whitespace();
    let command = parts.next().unwrap();
    let args = parts;

    match command {
        "cd" => {
            let new_dir = args.peekable().peek().map_or("/", |x| *x);
            let root = Path::new(new_dir);
            if let Err(e) = env::set_current_dir(&root) {
                eprintln!("{}", e);
            }
        },
        "exit" => return,
        command => {
                let mut child = Command::new(command)
                    .args(args)
                    .spawn();

                match child {
                    Ok(mut child) => { child.wait(); },
                    Err(e) => eprintln!("{}", e),
                };
        }
    }
    }
}