CODEWITHSUNDEEP
cposixrust
errordeveloper
errordeveloper

Reputation: 6912

Get file descriptor from `std::io::File::open`

I am writing binding for a C library, I'd like to call std::io::File::open as it's got error handling already. I then intend to pass the fd to C function.

I have looked at std::io::fs, but the fd field is nothing like what I would have thought.

After some more digging I found native::io::file::FileDesc, which indeed has fn fd(&self) -> fd_t, but doesn't seem like this is something I can access from an instance of std::io::File.

There appear to be fs_from_raw_fd method, it's the exact opposite to what I need.

Upvotes: 1

Views: 3324

Answers (2)

anil_khadwal
anil_khadwal

Reputation: 61

use std::os::unix::io::AsRawFd; 

let path = Path::new("my.txt");
let display = path.display();

let mut file = match File::open(&path) {
    // The `description` method of `io::Error` returns a string that
    // describes the error
    Err(why) => panic!("couldn't open {}: {}", display,
                                               why.description()),
    Ok(file) => file,
};
println!("file descriptor: {}",file.as_raw_fd());

Upvotes: 6

retep998
retep998

Reputation: 898

The closest you can get in the current version of Rust is via native::io::file::open.

use native::io::file::open;
use std::rt::rtio::{Open, Read};
let file = match open(&path.to_c_str(), Open, Read) {
    Ok(file) => file,
    Err(_) => return,
}
let fd = file.fd();

Upvotes: 2

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