原文:
https://www.raywenderlich.com/128039/command-line-programs-os-x-tutorial

练习写的代码:

https://github.com/uniquejava/Panagram

知识点:

取程序名
let executableName = (Process.arguments[0] as NSString).lastPathComponent

取命令行参数个数
let argCount = Process.argc

取参数数组(比如第一个参数)
let argument = Process.arguments[1]

字符串操作
截取
argument.substringFromIndex(argument.startIndex.advancedBy(1)))

替换:
self.lowercaseString.stringByReplacingOccurrencesOfString(" ", withString: "")

反转:
String(str.characters.reverse())

排序:
str.characters.sort()

去掉换行符
str = NSString(data: inputData, encoding: NSUTF8StringEncoding)!
str.stringByTrimmingCharactersInSet(NSCharacterSet.newlineCharacterSet())

扩展
命名StringExtension.swift
语法extension String{ func methodA() {}}

比较==
比较字符串相等,   
"hello" == "hello"
比较数组相等
["hello", "world"] == ["hello", "world"]

标准输入STDIN

func getInput() -> String {// 使用OC的API//1let keyboard = NSFileHandle.fileHandleWithStandardInput()//2let inputData = keyboard.availableData//3let strData = NSString(data: inputData, encoding: NSUTF8StringEncoding)!//4return strData.stringByTrimmingCharactersInSet(NSCharacterSet.newlineCharacterSet())// 或者使用swift中新的API//return readLine()!}

标准及错误输出STDOUT, STDERR

func writeMessage(message: String, to: OutputType = .Standard) {switch to {case .Standard:print("\u{001B}[;m\(message)")case .Error:fputs("\u{001B}[0;31m\(message)\n", stderr)}
}

定义enum

enum OutputType {case Errorcase Standard
}enum OptionType: String {case Palindrome = "p"case Anagram = "a"case Help = "h"case Quit = "q"case Unknowninit(value: String) {switch value {case "a":self = .Anagramcase "p":self = .Palindromecase "h":self = .Helpcase "q":self = .Quitdefault:self = .Unknown}}
}