如何在Cocoa中接收NSTask的输出？

import Foundation

let task = NSTask()

task.launchPath = "/usr/bin/ls"

task.arguments = ["-l"]

let pipe = NSPipe()

task.standardOutput = pipe

let fileHandle = pipe.fileHandleForReading

let data = fileHandle.readDataToEndOfFile()
let output = String(data: data, encoding: NSUTF8StringEncoding)

task.launch()

task.waitUntilExit()

print(output)

import Foundation

let task = NSTask()
task.launchPath = "/usr/bin/ls"
task.arguments = ["-l"]

let pipe = NSPipe()
task.standardOutput = pipe

let fileHandle = pipe.fileHandleForReading

task.launch()

let data = fileHandle.readDataToEndOfFile()
let output = String(data: data, encoding: NSUTF8StringEncoding)

task.waitUntilExit()

print(output)