Run external program concurrently and communicate with it through stdin / stdout

Question

I want to be able to run an external program concurrently with my Java code, i.e. I want to start the program, then return control to the calling method while keeping the ex

Answer 1

Have a look at ProcessBuilder. Once you've set up the ProcessBuilder and executed start you'll have a handle to a Process to which you can feed input and read output.

Here's a snippet to get you started:

ProcessBuilder pb = new ProcessBuilder("/bin/bash");
Process proc = pb.start();

// Start reading from the program
final Scanner in = new Scanner(proc.getInputStream());
new Thread() {
    public void run() {
        while (in.hasNextLine())
            System.out.println(in.nextLine());
    }
}.start();

// Write a few commands to the program.
PrintWriter out = new PrintWriter(proc.getOutputStream());
out.println("touch hello1");
out.flush();

out.println("touch hello2");
out.flush();

out.println("ls -la hel*");
out.flush();

out.close();

Output:

-rw-r--r-- 1 aioobe aioobe 0 2011-04-08 08:29 hello1
-rw-r--r-- 1 aioobe aioobe 0 2011-04-08 08:29 hello2