Interix is a POSIX conformant add-on for the Microsoft Windows operating systems.
Interix (also referred to as Microsoft SFU - Services For Unix) is an optional, POSIX-conformant Unix environment subsystem for Windows NT derived operating systems. Interix is a component of Windows Services for UNIX (SUA), and a superset of the Microsoft POSIX subsystem. Like the POSIX subsystem, Interix is an environment subsystem for the NT kernel. It includes numerous open source utility software programs and libraries.