I'm trying to run an interactive Linux process from Java. That is, a program which prompts the user for input as it runs. I want to catch the output and feed in appropriate responses.

When I try to run this, it hangs. The process sits there without terminating or emitting any output.
NB - I can run non-interactive processes fine.

Example code:

			

			// Utility class to empty the output streams using read()
			

			class StreamGobbler { ... }
			

			

			// Make a process
			

			Process process = new ProcessBuilder(MYCOMMAND).start();
			

			// any output?
			

			StreamGobbler outputGobbler = new StreamGobbler(process.getInputStream());
			

			// any error messages?
			

			StreamGobbler errorGobbler = new StreamGobbler(process.getErrorStream());
			

			// An input channel
			

			Writer in = new  new OutputStreamWriter(process.getOutputStream());
			

			// Wait for some output...
			

			while(true) {
			

			Methods.sleep(500);
			

			String out = outputGobbler.getString();
			

			if (out != "") { // But no output is ever received :(
			

			in.write("my response");
			

			in.flush();
			

			}
			

			}