Brahma Command Line Parser

在研究Brahma這個C#開源的Linq To GPU函式庫時，發現在Brahma網站上有釋出用來解析命令列參數的程式碼片段，稍微玩了一下，隨手做個記錄。

程式碼片段可在Code Snippets下載，透過程式碼片段管理員將其匯入至本機的Visual Studio中，程式碼片段如下：

#region CommandLine Arguments Parser

/* Simple commandline argument parser written by Ananth B. http://www.ananthonline.net */ static class CommandLine { public class Switch // Class that encapsulates switch data. { public Switch(string name, Action> handler, string shortForm) { Handler = handler; ShortForm = shortForm; }

public Switch(string name, Action> handler) { Handler = handler; ShortForm = null; }

public string Name { get; private set; } public string ShortForm { get; private set; } public Action> Handler { get; private set; }

public int InvokeHandler(string[] values) { Handler(values); return 1; } }

/* The regex that extracts names and comma-separated values for switches in the form ([=“value 1”,value2,…])+ / private static readonly Regex ArgRegex = new Regex(@"(?[^=\s]+)=?((?""?)(?(?(quoted)[^""]+|[^,]+))""?,?)", RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture | RegexOptions.IgnoreCase);

private const string NameGroup = “name”; // Names of capture groups private const string ValueGroup = “value”;

public static void Process(this string[] args, Action printUsage, params Switch[] switches) { /* Run through all matches in the argument list and if any of the switches match, get the values and invoke the handler we were given. We do a Sum() here for 2 reasons; a) To actually run the handlers and b) see if any were invoked at all (each returns 1 if invoked). If none were invoked, we simply invoke the printUsage handler. */ if ((from arg in args from Match match in ArgRegex.Matches(arg) from s in switches where match.Success && ((string.Compare(match.Groups[NameGroup].Value, s.Name, true) == 0) || (string.Compare(match.Groups[NameGroup].Value, s.ShortForm, true) == 0)) select s.InvokeHandler(match.Groups[ValueGroup].Value.Split(’,’))).Sum() == 0) printUsage(); // We didn’t find any switches } }

#endregion

該程式碼片段結合擴充方法、Linq、與正規表示式等技術去實現解析命令列參數的功能，解析時會去比對設定的Switch命令類別，藉此將命令列參數解析後帶入給對應的命令去處理。

使用時直接在傳入的命令列參數上呼叫Process

args.Process(顯示命令使用說明的函式，命令處理類別集合);

其中命令處理類別在建構時需帶入命令名稱、命令對應處理函式、命令縮寫。

new CommandLine.Switch (命令名稱,命令對應處理函式,命令縮寫);

使用上會像下面這樣：

args.Process(printUsage,new CommandLine.Switch []{ new CommandLine.Switch ("-Command1",Command1,"-cmd1") });

static void Command1(IEnumerable args) { … }

static void printUsage() { … }

這邊直接來看個簡單的使用範例：

static void Main(string[] args) {

args.Process(printUsage,new CommandLine.Switch []{ new CommandLine.Switch ("-MessageBox",MessageBoxCommand,"-mbx"), new CommandLine.Switch ("-ConsoleWriteLine",ConsoleWriteLineCommand,"-cw") }); }

static void printUsage() { Console.WriteLine(“測試解析命令列參數用命令”); Console.WriteLine(); Console.WriteLine("-MessageBox or -mbx: 彈出對話方塊"); Console.WriteLine("-ConsoleWriteLine or -cw: 顯示主控台訊息"); }

static void MessageBoxCommand(IEnumerable args) { System.Windows.Forms.MessageBox.Show(args.FirstOrDefault()); }

static void ConsoleWriteLineCommand(IEnumerable args) { Console.WriteLine(args.FirstOrDefault()); }

以這範例來看，若在命令列參數帶入-cw=test的話：

帶入參數-mbx=test的話：

不帶任何參數或是非合法的參數的話：

使用起來感覺程式還算十分清楚好維護，在撰寫上也很容易上手，但是彈性上卻稍嫌不足，像是命令名稱與值要用等號隔開、名稱與值中間不能有空格、無法處理不合法參數…等等，使用上這邊要特別注意一下。

Download

CommandLineParser.zip

Link

Code Snippets