use command_fds::{CommandFdExt, FdMapping};
use std::fs::File;
use std::io::stdin;
use std::os::fd::AsFd;
use std::os::unix::io::AsRawFd;
use std::process::Command;

// Open a file.
let file = File::open("Cargo.toml").unwrap();

// Prepare to run `ls -l /proc/self/fd` with some FDs mapped.
let mut command = Command::new("ls");
command.arg("-l").arg("/proc/self/fd");
command
    .fd_mappings(vec![
        // Map `file` as FD 3 in the child process.
        FdMapping {
            parent_fd: file.into(),
            child_fd: 3,
        },
        // Map this process's stdin as FD 5 in the child process.
        FdMapping {
            parent_fd: stdin().as_fd().try_clone_to_owned().unwrap(),
            child_fd: 5,
        },
    ])
    .unwrap();

// Spawn the child process.
let mut child = command.spawn().unwrap();
child.wait().unwrap();