1 use std::env; 2 use std::fs::File; 3 use std::io::Write; 4 use std::path::PathBuf; 5 main()6 fn main() { 7 let dst = PathBuf::from(&env::var("OUT_DIR").unwrap()); 8 let mut f = File::create(&dst.join("hello.rs")).unwrap(); 9 f.write_all(b" 10 pub const ANSWER: u32 = 40 + 2; 11 ").unwrap(); 12 } 13