Calling fork() from Swift

fork.swift

// Note: calling fork() can be unsafe and dangerous, that
// is why Swift doesn't let you invoke it directy. Be very
// careful about how you use fork(). For some more details,
// see https://www.evanjones.ca/fork-is-dangerous.html and
// http://www.sealiesoftware.com/blog/archive/2017/6/5/Objective-C_and_fork_in_macOS_1013.html

import Darwin

let RTLD_DEFAULT = UnsafeMutableRawPointer(bitPattern: -2)
let forkPtr = dlsym(RTLD_DEFAULT, "fork")
typealias ForkType = @convention(c) () -> Int32
let fork = unsafeBitCast(forkPtr, to: ForkType.self)

switch fork() {
case -1:
    print("Error")
case 0:
    print("Child")
default:
    print("Parent")
}