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<IEnumerable<string>> handler, string shortForm)
{
Name = name;
Handler = handler;
ShortForm = shortForm;
}

    public Switch(string name, Action&lt;IEnumerable&lt;string&gt;&gt; handler)
    {
        Name = name;
        Handler = handler;
        ShortForm = null;
    } 

    public string Name
    {
        get;
        private set;
    }
    public string ShortForm
    {
        get;
        private set;
    }
    public Action&lt;IEnumerable&lt;string&gt;&gt; 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 (&lt;switch&gt;[="value 1",value2,...])+ */
private static readonly Regex ArgRegex =
    new Regex(@"(?&lt;name&gt;[^=\s]+)=?((?&lt;quoted&gt;\""?)(?&lt;value&gt;(?(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 &amp;&amp;
             ((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&lt;string&gt; args)
{
    ...
} 

static void printUsage()
{            
    ...
} </pre>



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&lt;string&gt; args)
{
    System.Windows.Forms.MessageBox.Show(args.FirstOrDefault());
} 

static void ConsoleWriteLineCommand(IEnumerable&lt;string&gt; args)
{
    Console.WriteLine(args.FirstOrDefault());
} </pre>



以這範例來看,若在命令列參數帶入-cw=test的話:


image



帶入參數-mbx=test的話:


image



不帶任何參數或是非合法的參數的話:


image



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