use std::process::{Child, Command, Stdio};
use std::os::unix::prelude::*;
use std::fs::File;
use std::io;

struct Redirect {
    pager: Child,
}

fn redirect_stdout() -> io::Result<Redirect> {
    let mut pager = Command::new("less")
        .stdin(Stdio::piped())
        .arg("-FR")
        .spawn()?;
    let stdin = pager.stdin.take().unwrap();

    unsafe {
        // redirect our stdout/stderr to the `less` child process
        if libc::dup2(stdin.as_raw_fd(), libc::STDOUT_FILENO) < 0 {
            return Err(io::Error::last_os_error())
        }
        if libc::dup2(stdin.as_raw_fd(), libc::STDERR_FILENO) < 0 {
            return Err(io::Error::last_os_error())
        }
    }
    Ok(Redirect { pager })
}

impl Drop for Redirect {
    fn drop(&mut self) {
        unsafe {
            let null = File::open("/dev/null").unwrap();
            // "close" stdio streams now that our program is done
            assert!(libc::dup2(null.as_raw_fd(), libc::STDIN_FILENO) >= 0);
            assert!(libc::dup2(null.as_raw_fd(), libc::STDOUT_FILENO) >= 0);
            assert!(libc::dup2(null.as_raw_fd(), libc::STDERR_FILENO) >= 0);
        }

        self.pager.wait().unwrap();
    }
}

fn main() {
    let _pager = redirect_stdout().unwrap();

    for i in 0..100 {
        println!("wut: {}", i);
    }
}