運行時問題

Question

如何使這個工作在Windows上，文件filename.txt沒有被創建。

Process p = Runtime.getRuntime().exec("cmd echo name > filename.txt"); 

顯然，期望輸出是一個 「FILENAME.TXT」 應被創建（C：\ Documents和Settings \用戶名\ FILENAME.TXT）與內容 「名稱」。

---

之所以能夠用下面的代碼來管理，即使該文件是 「FILENAME.TXT」 不被用的ProcessBuilder

 Runtime runtime = Runtime.getRuntime(); 
     Process process = runtime.exec("cmd /c cleartool lsview"); 
     // Directly to file 

//Process p = Runtime.getRuntime().exec( 
//    new String[] { "cmd", "/c", "cleartool lsview > filename.txt" },null, new File("C:/Documents and Settings/username/")); 

     InputStream is = process.getInputStream(); 
     InputStreamReader isr = new InputStreamReader(is); 
     BufferedReader br = new BufferedReader(isr); 
     String line; 

     System.out.printf("Output of running %s is:", 
      Arrays.toString(args)); 

     while ((line = br.readLine()) != null) { 
     System.out.println(line); 
     } 

或使用ProceessBuilder創建，

Process process = new ProcessBuilder("cmd", "/c", "cleartool lsview").start(); 
InputStream is = process.getInputStream(); 
BufferedReader br = new BufferedReader(new InputStreamReader(is)); 

System.out.printf("Output of running %s is:", Arrays.toString(args)); 

String line; 
while ((line = br.readLine()) != null) { 
    System.out.println(line); 
} 

Answer 1

你實際上應使用ProcessBuilder而不是Runtime.exec（請參閱the docs）。

ProcessBuilder pb = new ProcessBuilder("your_command", "arg1", "arg2"); 
pb.directory(new File("C:/Documents and Settings/username/")); 

OutputStream out = new FileOutputStream("filename.txt"); 
InputStream in = pb.start().getInputStream(); 

byte[] buf = new byte[1024]; 
int len; 
while ((len = in.read(buf)) > 0) 
    out.write(buf, 0, len); 

out.close(); 

（我會適應它cmd並呼應，如果我有一個窗口機在到達...隨意編輯這個職位！）

Answer 2

它應該與

Process p = Runtime.getRuntime().exec(
    new String[] { "cmd", "/c", "echo name > filename.txt" }); 

我目前沒有運行Windows，所以很不幸我無法測試它。

背後的原因是，在您的版本中，命令在每個空格字符處被分割。因此，運行時所要做的是創建一個進程cmd併爲其提供參數echo,name,>和filename.txt，這是沒有意義的。命令echo name > filename.txt是cmd進程的單個參數，因此您必須手動爲不同參數提供一個數組。

如果你想確保該文件是在一個特定的文件夾中創建你必須提供一個工作目錄exec()僅在三個參數版本的工作原理：

Process p = Runtime.getRuntime().exec(
    new String[] { "cmd", "/c", "echo name > filename.txt" }, 
    null, new File("C:/Documents and Settings/username/"));