With the launch of the open source Swift project, we are also releasing a port that works with the Linux operating system! You can build it from the Swift sources or download pre-built binaries for Ubuntu. The port is still a work in progress but we’re happy to say that it is usable today for experimentation. Currently x86_64 is the only supported architecture on Linux.

Here are a few highlights of what’s working in the port today:

• Swift without the Objective-C Runtime: Swift on Linux does not depend on the Objective-C runtime nor includes it. While Swift was designed to interoperate closely with Objective-C when it is present, it was also designed to work in environments where the Objective-C runtime does not exist.

• The core Swift Language and Standard Library on Linux shares most of the same implementation and APIs as on Apple platforms. There are some slight differences of behavior because of the absence of the Objective-C runtime on Linux (noted below).

• The Glibc Module: Most of the Linux C standard library is available through this module similar to the Darwin module on Apple platforms. Some headers aren’t yet imported into the module, such as tgmath.h.

  To try it out, just import Glibc.

• Swift Core Libraries: The Core Libraries provide implementations of core APIs from Foundation and XCTest to be used on Linux without Objective-C . The intention is that these APIs are available in a cross-platform manner regardless of whether you are using Swift on Apple’s platforms or Swift on Linux.

• LLDB Swift debugging and the REPL: You can debug your Swift binaries and experiment in the REPL just like you do on macOS.

• The Swift Package Manager is a first class citizen as it is on Apple’s platforms.

Here are some things that aren’t quite working yet or are planned for the future:

• libdispatch: Part of the Core Libraries, updated Linux support is in progress. You can follow development on the libdispatch project on GitHub.

• Some C APIs: Although this is generally true for all of our supported platforms, a few constructs in C aren’t imported yet into Swift. This will cause some APIs to be unavailable, such as those that contain varargs / va_list. However, in recent months Swift’s interoperability with C has significantly advanced, gaining support for named and anonymous unions, anonymous structs, and bitfields.

• Some String APIs: The Standard Library’s String is missing implementations of several important APIs because they are currently tied to the implementation of NSString on Apple’s platforms.

• Runtime Introspection: When a Swift class on Apple’s platforms is marked @objc or subclasses NSObject you can use the Objective-C runtime to enumerate available methods on an object or call methods using selectors. Such capabilities are absent because they depend on the Objective-C runtime.

• Array<T> as? Array<S>: Some mechanisms, such as casting containers with different associated types, currently do not work as they relied on bridging mechanisms with Objective-C.

We’re really excited to be able to release the open source project with a great head start for Linux support that you can try right now! There is still plenty of work to be done, so we hope to see you contribute to Swift to make the Linux port even more complete.