Swift 4.1 on macOS

swift-4.1-macos.md

1. Download latest "Swift 4.1 Development" snapshot from Swift.org Snapshots.
2. Open downloaded .pkg file to install.
3. Xcode > Toolchains > Swift 4.1 Snapshot

We can do this in for terminal like

johny-imac:~ johnykutty$ swift --version
Apple Swift version 4.0 (swiftlang-900.0.65 clang-900.0.37)
Target: x86_64-apple-macosx10.9
johny-imac:~ johnykutty$ ls /Library/Developer/Toolchains
swift-3.0-PREVIEW-6.xctoolchain				swift-4.1-DEVELOPMENT-SNAPSHOT-2018-01-30-a.xctoolchain	swift-latest.xctoolchain
johny-imac:~ johnykutty$ /usr/libexec/PlistBuddy -c "Print CFBundleIdentifier:" /Library/Developer/Toolchains/swift-4.1-DEVELOPMENT-SNAPSHOT-2018-01-30-a.xctoolchain/Info.plist
org.swift.4120180130a
johny-imac:~ johnykutty$  export TOOLCHAINS=org.swift.4120180130a
johny-imac:~ johnykutty$ swift --version
Apple Swift version 4.1-dev (LLVM 4d75b446be, Clang db92199adc, Swift 990b05adc6)
Target: x86_64-apple-darwin16.7.0
johny-imac:~ johnykutty$ 

Be sure you select "Install for all users" when you install, or else the toolchain won't be placed in the directory above

There is a snapshot in the Vapor APT for Linux:
sudo apt-get install swift-beta