A process that repeatedly executes itself

fork_bomb.rs

use std::process::Command;
use std::env;
use std::process;
use std::time::SystemTime;
use crossbeam; // 0.7.3;

pub fn main() {
    let myself = env::current_exe().expect("no current exe");
    let n: u64 = env::args()
                    .enumerate()
                    .find(|&(i, _)| i == 1)
                    .and_then(|(_, s)| s.parse().ok())
                    .unwrap_or(0);
    


    crossbeam::scope(|s| {
    loop{
        s.spawn( |_| {
            loop{
                let res = Command::new(&myself)
                        .args( &[ (n+1).to_string() ] )
                        .spawn()
                        .expect("failed to execute process");
                println!("{}spawned process {} from {} (generation {}) (time: {:?})", 
                    Spaces(n),
                    res.id(),
                    process::id(),
                    n,
                    SystemTime::now()
                );
            }
        });
    }
    }).expect("no scope");
}

struct Spaces(u64);

impl std::fmt::Display for Spaces {
    fn fmt(&self, f:&mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for _ in 0..self.0 {
            f.write_str(" ")?
        }
        Ok(())
    }
}