How do I convert an OsString to a u16 on POSIX systems?

Question

I'm grabbing a string from the environment via std::env::var_os, and I want to attempt to convert the resulting OsString received from matching the returned Option<OsString> into a u16. How could I go about doing this in a way that works on POSIX systems?

Answer 1

If you'd like to convert an Option<OsString> to an Option<u16> you can use this function:

use std::ffi::OsString;

fn to_integer(maybe_os_string: Option<OsString>) -> Option<u16> {
    if let Some(os_string) = maybe_os_string {
        if let Ok(string) = os_string.into_string() {
            if let Ok(integer) = string.parse::<u16>() {
                return Some(integer);
            }
        }
    }
    None
}

playground

It should work regardless of underlying operating system. The caller of the function would have to handle the None case if the OsString can't be parsed as a u16.