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);
}

• Stargateur: Actually this answer cover almost all I could say.
• Genuinebyte: @Stargateur Thanks a lot! I forgot to mention I didn't want to use any external crates so that works really well for me.

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.

• Genuinebyte: I didn't realize env::Args implemented the Iterator trait. It's definitely more elegant than my code, thanks!
• Brandon Clark: Thank you. Honestly there are more cool tricks, I think you can get away with just join no 'if'.
• Shepmaster: @Genuinebyte I didn't realize env::Args implemented the Iterator trait. — where did you think collect was coming from?
• Roland Illig: What if you just omitted the if args.len() == 0 branch completely? That would make the code even shorter.

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!();
}