I'm not confident enough to say this for sure, but I think you are off base. I created a demo in the Rust playground [0] which shows that there is no implicit

I'm not confident enough to say this for sure, but I think you are off base. I created a demo in the Rust playground [0] which shows that there is no implicit environment variable expansion. Also, the source for `std::process:Command` [1] looks to be calling into libc to perform a fork/exec. That said, this is rather new territory for me, so let me know if I'm missing something here. [0] : https://play.rust-lang.org/?version=stable&mode=debug&edition=2015&gist=54b9b60c2b2b7ea84ed1f2e433024043 https://play.rust-lang.org/?version=stable&mode=debug&editio... [1] : https://github.com/rust-lang/rust/blob/master/src/libstd/sys/unix/process/process_unix.rs#L52 https://github.com/rust-lang/rust/blob/master/src/libstd/sys...