Function pidfd_getfd

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

Available on crate feature dep_nc only.

Obtain a duplicate of another process’s file descriptor.

Examples

const STDOUT_FD: i32 = 1;

let pid = unsafe { nc::fork() };

assert!(pid.is_ok());
let pid = pid.unwrap();
if pid == 0 {
    println!("In child process, pid: {}", unsafe { nc::getpid() });
    let path = "/tmp/nc-pidfdopen";
    let fd = unsafe {
        nc::openat(
            nc::AT_FDCWD,
            path,
            nc::O_CREAT | nc::O_WRONLY | nc::O_TRUNC,
            0o644,
        )
    };
    assert!(fd.is_ok());
    let fd = fd.unwrap();
    let ret = unsafe { nc::dup3(fd, STDOUT_FD, 0) };
    assert!(ret.is_ok());
    println!("[child] stdout redirected to file!");

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

println!("[parent] child pid: {}", pid);

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

let pidfd = unsafe { nc::pidfd_open(pid, 0) };
if pidfd == Err(nc::errno::ENOSYS) {
    eprintln!("PIDFD_OPEN syscall not supported in this system");
    return;
}
let pidfd = pidfd.unwrap();

let child_stdout_fd = unsafe { nc::pidfd_getfd(pidfd, STDOUT_FD, 0) };
if child_stdout_fd == Err(nc::errno::ENOSYS) {
    eprintln!("PIDFD_OPEN syscall not supported in this system");
    return;
}
let child_stdout_fd = child_stdout_fd.unwrap();
let msg = b"Hello, msg from parent process\n";
let ret = unsafe { nc::write(child_stdout_fd, msg) };
assert!(ret.is_ok());
let nwrite = ret.unwrap();
assert_eq!(nwrite as usize, msg.len());

let ret = unsafe { nc::close(pidfd) };
assert!(ret.is_ok());
let ret = unsafe { nc::close(child_stdout_fd) };
assert!(ret.is_ok());