Demonstrate launching an `NSTask` and asynchronously reading its output.

testTaskOutputPipe.swift

import Cocoa

/// Demonstrate launching an `NSTask` and asynchronously reading its output.
///
/// Credit: <http://stackoverflow.com/a/23938137/1175>

func testTaskOutputPipe() {
    let task = NSTask()
    task.launchPath = "/bin/ls"
    task.arguments = ["-l", "/Applications"]

    let stdoutPipe = NSPipe()
    task.standardOutput = stdoutPipe

    let stdoutHandle = stdoutPipe.fileHandleForReading
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0)) {
        var data = stdoutHandle.availableData
        while data.length > 0 {
            if let s = NSString(data: data, encoding: NSUTF8StringEncoding) {
                print(s, terminator: "")
                data = stdoutHandle.availableData
            }
        }
    }

    task.launch()
    task.waitUntilExit()
}

testTaskOutputPipe()