really.rs

use std::{os::unix::prelude::ExitStatusExt, process::ExitCode};

fn main() -> std::io::Result<ExitCode> {
    let (cmd, args) = match std::env::args().nth(1) {
        Some(cmd) => (cmd, std::env::args().skip(2).collect::<Vec<String>>()),
        None => {
            eprintln!(
                "Usage: {} <command> [args...]",
                std::env::args().next().unwrap()
            );
            return Ok(ExitCode::FAILURE);
        }
    };

    let max_sleep = 30;
    let mut sleep = 1;
    loop {
        let mut command = std::process::Command::new(&cmd).args(&args).spawn()?;
        let status = command.wait()?;

        let signal = status.signal();
        let code = status.code();

        match (signal, code) {
            (_, Some(0)) => break,
            (Some(9), _) => {
                eprintln!("{}: terminated by signal 9. Exiting", cmd);
                break;
            }
            (Some(signal), _) => {
                eprintln!("{}: terminated by signal {}. Retrying in {} seconds", cmd, signal, sleep);
            }
            (_, Some(code)) => {
                eprintln!("{}: exited with status {}. Retrying in {} seconds", cmd, code, sleep);
            }
            (None, None) => {
                eprintln!("{}: terminated by unknown means. Retrying in {} seconds", cmd, sleep);
                break;
            }
        }
        std::thread::sleep(std::time::Duration::from_secs(sleep));
        sleep = std::cmp::min(sleep * 2, max_sleep);
    }

    Ok(ExitCode::SUCCESS)
}