Catching InputStream from Runtime/Process

[Prashant Sehgal]

I have a .cmd file - say - with the following code:

 echo "I am a command that produces a lot of text output"   

I want to invoke this using Runtime.getRuntime().exec(.) and catch the "I am a command that produces a lot of text output" text in the InputStream being returned from the Process.

The problem is that I *must* start this command in a separate DOS window. In doing that, my program loses the handle to the stream and does not return any text from the command file.

So, how do I start the command in a separate window while still being able to catch all it's output in my Process's inputstream?

[Campbell Ritchie]

Originally posted by Prashant Sehgal:
The problem is that I *must* start this command in a separate DOS window.

By using a DOS window, are you tying yourself to a particular operating system? You need to read Michael Daconta's classic article (Google for "when Runtime.exec() won't") before even thinking of using Runtime.exec(). That tells you how to get all the output from the Streams, and the newer ProcessBuilder class makes that easier, but I think your output will be redirected to the original terminal window.

[Prashant Sehgal]

Yes this is a Microsoft only deployment.

[Prashant Sehgal]

The output is not getting redirected to the original terminal window. I anyway want the output to display in the a new terminal window and also to catch it in the Processes's inputstream. I'll check out the ProcessBuilder class and the article you mention as well.

But my original problem stands.

How to catch the inputstream from a new DOS window that has been created by "exec()ing" a .cmd script from within your java program.

[Prashant Sehgal]

This might illustrate better:

Java Code:

  public static void main(String args[]) {
try
{
ProcessBuilder pb = new ProcessBuilder("c:/test_1.cmd");
Map<String, String> env = pb.environment();
 
Process p = pb.start();

 
BufferedReader br = new BufferedReader (new InputStreamReader(p.getInputStream()));
String line = "";
while ((line=br.readLine())!=null) {
System.out.println(line);
}
}
catch (Exception e)
{
e.printStackTrace();
}
  

Cmd Script: test_1.cmd

  start /separate test_2.bat  

Bat Script:

  echo "this is test 2"  

I want my original program to return "this is test 2" in it's inputstream. Is it even possible?