rustup.sh now is interactive, and asks for confirmation before continuing.
Installation is like:
$ curl -sSL https://static.rust-lang.org/rustup.sh | sh
Which will print:
Welcome to Rust. This script will download the Rust compiler and its package manager, Cargo, and install them to /usr/local. You may install elsewhere by running this script with the --prefix=<path> option. The installer will run under 'sudo' and may ask you for your password. If you do not want the script to run 'sudo' then pass it the --disable-sudo flag. You may uninstall later by running /usr/local/lib/rustlib/uninstall.sh, or by running this script again with the --uninstall flag. Continue? (y/N)