Function nc::pidfd_getfd

pub fn pidfd_getfd(pidfd: i32, target_fd: i32, flags: u32) -> Result<i32, Errno>

Obtain a duplicate of another process’s file descriptor.

let pid = nc::fork();
assert!(pid.is_ok());
if pid == Ok(0) {
    println!("In child process, pid: {}", nc::getpid());
    let path = "/tmp/nc-pidfdopen";
    let fd = nc::openat(
        nc::AT_FDCWD,
        path,
        nc::O_CREAT | nc::O_WRONLY | nc::O_TRUNC,
        0o644,
    );
    assert!(fd.is_ok());
    let fd = fd.unwrap();
    assert!(nc::dup2(fd, STDOUT_FD).is_ok());
    println!("[child] stdout redirected to file!");

    let t = nc::timespec_t {
        tv_sec: 2,
        tv_nsec: 0,
    };
    assert!(nc::nanosleep(&t, None).is_ok());
    let _ = nc::close(fd);
    let _ = nc::unlink(path);
    nc::exit(0);
}

let pid = pid.unwrap();
println!("[parent] child pid: {}", pid);

let t = nc::timespec_t {
    tv_sec: 2,
    tv_nsec: 0,
};
assert!(nc::nanosleep(&t, None).is_ok());

let pidfd = nc::pidfd_open(pid, 0);
assert!(pidfd.is_ok());
let pidfd = pidfd.unwrap();

let ret = nc::pidfd_getfd(pidfd, STDOUT_FD, 0);
println!("ret: {:?}", ret);
if let Err(errno) = ret {
    eprintln!("pidfd_getfd() failed, err: {}", nc::strerror(errno));
}
let child_stdout_fd = ret.unwrap();
let msg = "Hello, msg from parent process\n";
let ret = nc::write(child_stdout_fd, msg.as_ptr() as usize, msg.len());
assert!(ret.is_ok());
let nwrite = ret.unwrap();
assert_eq!(nwrite as usize, msg.len());

let _ = nc::close(pidfd);
let _ = nc::close(child_stdout_fd);