Thread: ProcessBuilder and I/O

I'm trying to get my head around the ProcessBuilder class, so I built this test class. Needless to say, it doesn't work, but I can't figure out why. Here's the code:

import java.io.*;
 
 
/*Test Class*/
public class TestMe
{
	public static void main(String[] args)
	{
		ProcessBuilder pb = null;
		Process shell = null;
		BufferedReader fromProcess = null;
		BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter toProcess = null;
		String command = "";
		String line = "";
 
		try
		{
			System.out.printf("-------------\n");
			System.out.printf("Testing Process Builder%n");
			pb = new ProcessBuilder ("/bin/bash");
			System.out.printf("Merge stdout with stderr? %b%n", pb.redirectErrorStream());
			if (pb.redirectErrorStream() != true)
			{
				System.out.printf("\tMerging both streams%n");
				pb.redirectErrorStream(true);
				System.out.printf("\tIt is now %b%n", pb.redirectErrorStream());
			}
 
			System.out.printf("Creating Shell process\n");
			shell = pb.start();
			System.out.printf("Getting stdout\n");
			fromProcess = new BufferedReader (new InputStreamReader (shell.getInputStream()));
			System.out.printf("Getting stdin\n");
			toProcess = new PrintWriter (shell.getOutputStream(), true);
 
			System.out.printf("Time to pass a command!%n");
			System.out.printf("\tstdin :- ");
			command = input.readLine();
			System.out.printf("\tCommand is: %s%n", command);
			System.out.printf("Handing command over to process...%n");
			toProcess.print(command);
 
			System.out.printf("Getting output...%n");
			do
			{
				line = fromProcess.readLine();
				System.out.printf("\t%s%n",line);
			} while (line != null);
 
			//Close I/O
			toProcess.close();
			fromProcess.flush();
			fromProcess.close();
 
			System.printf("It Worked!%n");
 
		}
		catch (Exception e)
		{
			System.out.printf("%nError: %s%n", e.getMessage());
			e.printStackTrace();
		}
 
	} //End main method
 
} //End class TestMe

In my head, I should be able to pass a command (say, "ls") and get the output of the command printed out to the screen. Where am I going wrong? Any help would be greatly appreciated.


Zo...

See this article: When Runtime.exec() won't - JavaWorld