How do I launch a completely independent process from a Java program?

There is a parent child relation between your processes and you have to break that. For Windows you can try:

Runtime.getRuntime().exec("cmd /c start editor.exe");

For Linux the process seem to run detached anyway, no nohup necessary. I tried it with gvim, midori and acroread.

import java.io.IOException;
public class Exec {
    public static void main(String[] args) {
        try {
            Runtime.getRuntime().exec("/usr/bin/acroread");
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println("Finished");
    }
}

I think it is not possible to to it with Runtime.exec in a platform independent way.

for POSIX-Compatible system:

 Runtime.getRuntime().exec(new String[]{"/bin/sh", "-c", "your command"}).waitFor();

I have some observations that may help other people facing similar issue.

When you use Runtime.getRuntime().exec() and then you ignore the java.lang.Process handle you get back (like in the code from original poster), there is a chance that the launched process may hang.

I have faced this issue in Windows environment and traced the problem to the stdout and stderr streams. If the launched application is writing to these streams, and the buffer for these stream fills up then the launched application may appear to hang when it tries to write to the streams. The solutions are:

1. Capture the Process handle and empty out the streams continually - but if you want to terminate the java application right after launching the process then this is not a feasible solution
2. Execute the process call as cmd /c <<process>> (this is only for Windows environment).
3. Suffix the process command and redirect the stdout and stderr streams to nul using 'command > nul 2>&1'

It may help if you post a test section of minimal code needed to reproduce the problem. I tested the following code on Windows and a Linux system.

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {
        Runtime.getRuntime().exec(args[0]);
    }
}

And tested with the following on Linux:

java -jar JustForTesting.jar /home/monceaux/Desktop/__TMP/test.sh

where test.sh looks like:

#!/bin/bash
ping -i 20 localhost

as well as this on Linux:

java -jar JustForTesting.jar gedit

And tested this on Windows:

java -jar JustForTesting.jar notepad.exe

All of these launched their intended programs, but the Java application had no problems exiting. I have the following versions of Sun's JVM as reported by java -version :

• Windows: 1.6.0_13-b03
• Linux: 1.6.0_10-b33

I have not had a chance to test on my Mac yet. Perhaps there is some interaction occuring with other code in your project that may not be clear. You may want to try this test app and see what the results are.

You want to launch the program in the background, and separate it from the parent. I'd consider nohup(1).