Earlier this year, Apple engineers announced swift system as their new low-level system interface library. At present, they have opened the swift system and introduced Linux support. Swift supports access to C interfaces, but the goal of the Swift System is to provide a normal Swift interface for low-level system libraries.
Swift system provides separate APIs and behaviors based on the platform and its capabilities. Although the current form of swift also adds Linux support, it can not fully support every system call.
If you want to know more about swift system, open source and new Linux support, you can go to Swift.org Blog to understand.