Rust Echo Command Implementation

Question

I'm just starting out in Rust and I find the concept of ownership confusing so I wrote an implementation of the echo command. I would like to know if I could have set the initial value on the echo variable any better or just any general improvements.

use std::env;

fn main() {
    let args: Vec<String> = env::args().collect();

    let mut echo: String;
    if let Some(string) = args.get(1) {
        echo = string.to_string();
    } else {
        return;
    }

    for arg in &args[2..] {
        echo.push(' ');
        echo.push_str(arg.as_str());
    }
    echo.push('\n');

    println!("{}", echo);
}

Answer 1

I would not say I am any more proficient but I would make these changes if I wrote it.

• skip(1) first arg.
• join(" ") instead of iterate though args.

You do not need a mutable value.

use std::env;

fn main() {
    let args: Vec<String> = env::args().skip(1).collect();

    if args.len() == 0 {
        println!("");
    } else {
        println!("{}", args.join(" "));
    }
}

I would do one more thing and send to stdout since your mimicking echo, but maybe much for this answer.

Answer 2

1. Use Iterator::skip instead of collecting the arguments into a Vec and then skipping over it.

2. This implementation should not have any allocation, whatsoever. Neither collecting the arguments or building an output string is needed.

use std::env;

fn main() {
    let mut args = env::args().skip(1);

    if let Some(arg) = args.next() {
        print!("{}", arg);

        for arg in args {
            print!(" {}", arg);
        }
    }

    println!();
}