Swiftをシェルスクリプトのように使う一番簡単な方法

#!/usr/bin/swift

let hello = "こんにちは"
print(hello)

// 遊び心で。。
let 挨拶 = "お世話になります"
print(挨拶)

$ chmod a+x hello.swift

$ ./hello.swift

$ /usr/bin/swift --version
Apple Swift version 2.1 (swiftlang-700.1.101.6 clang-700.1.76)
Target: x86_64-apple-darwin15.0.0

#!/usr/bin/swift

import Foundation

typealias Failure = (NSError!) -> Void
typealias ResultBlock = (NSData!, NSError!) -> Void

/// JSONObjectWithDataの戻り値として使用する
enum JSONObjectWithDataResult {
    case Success(AnyObject)
    case Failure(NSError)
}

/// NSDataをJSONオブジェクトに変換し、JSONオブジェクトまたはエラーのいずれかを返す
func JSONObjectWithData(data: NSData) -> JSONObjectWithDataResult {
    do {
        let json = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments)
        return .Success(json)
    } catch let error as NSError {
        return .Failure(error)
    }
}

/// JSONデータの取得
func fetchJSONData(block: ResultBlock) {
    let url = NSURL(string: "http://api.tiqav.com/search/random.json")
    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config)
    let task = session.dataTaskWithURL(url!) { data, response, error in
        guard let data = data else {
            block(nil, error)
            return
        }
        session.invalidateAndCancel()
        dispatch_async(dispatch_get_main_queue()) { () in
            block(data, nil)
        }
    }
    task.resume()
}

var waitingForBlock = true // 終了判定で使用する

fetchJSONData() { data, error in

    guard let data = data else {
        print("エラー: \(error)")
        return
    }

    switch JSONObjectWithData(data) {
    case .Success(let json):
        print("json: \(json)")
        for item in json as! [NSDictionary] {
            print(item.objectForKey("source_url"))
        }
    case .Failure(let error):
        print("エラー: \(error)")
    }

    waitingForBlock = false
}

while waitingForBlock {
    // １秒毎に終了を確認する
    NSRunLoop.currentRunLoop().runMode(NSDefaultRunLoopMode, beforeDate: NSDate(timeIntervalSinceNow:1.0))
}

#!/usr/bin/swift

import Foundation

let task = NSTask()
task.launchPath = "/bin/sh"
task.arguments = ["-c", "ls -l ./"]
task.standardInput = NSFileHandle.fileHandleWithNullDevice()
task.standardError = NSFileHandle.fileHandleWithStandardError()
task.standardOutput = NSFileHandle.fileHandleWithStandardOutput()
task.launch()
task.waitUntilExit()