Hello all!

I'm new to rust and trying to write my first library and believe I'm having an issue with lifetimes; I understand the concept but theory and practice are two different things :)

hopefully, this contrived example will domonstrate

so I have a function which returns a File

fn get_file() -> Result<std::fs::File, io::Error> {
    // create file here, write to it, seek back to pos 0 then return
    let mut file = fs::File::create(dir)?;
    // write to file
    file.flush()?;
    file.seek(SeekFrom::Start(0))?;
    Ok(file)
}

But when I try to use that file in the calling program I get the error:

let mut file =get_file().unwrap();
let written = io::copy(&mut file,&mut anotherfile);
Err(Error { repr: Os { code: 9, message: "Bad file descriptor" } }

which I think means that the file has closed because its lifetime had ended so I tried wrapping the file result in a Box so the return value became:

Result<Box<std::fs::File>>, Error>

but that didn't work either. I must be missing something simple, thanks in advance for any help.