runas allows an administrator to run a process as any user on a Unix operating system, including the super-user in a non-interactive manner without having to login as that user . Additionally, it provides a secure way for allowing normally unpriviledged users to execute selected programs as a super-user (or any other user on the system) in a secure manner.
You can download it from the following link: https://packetstormsecurity.com/files/download/13339/runas-3.11.0.tgz
Source: https://packetstormsecurity.com/files/13339/runas-3.11.0.tgz.html