Function nc::wait4

pub fn wait4(
    pid: pid_t, 
    wstatus: &mut i32, 
    options: i32, 
    rusage: &mut rusage_t
) -> Result<pid_t, Errno>

Wait for process to change state.

let ret = nc::fork();
match ret {
    Err(errno) => {
        eprintln!("fork() error: {}", nc::strerror(errno));
        nc::exit(1);
    }
    Ok(0) => println!("[child] pid is: {}", nc::getpid()),
    Ok(pid) => {
        let mut status = 0;
        let mut usage = nc::rusage_t::default();
        let ret = nc::wait4(-1, &mut status, 0, &mut usage);
        assert!(ret.is_ok());
        println!("status: {}", status);
        let exited_pid = ret.unwrap();
        assert_eq!(exited_pid, pid);
    }
}