Java – Terminate child processes spawned by a ProcessBuilder on *nix

java

I'm executing a shell pipeline from a java program – it'll be something like

ProcessBuilder builder = new ProcessBuilder(
                         "sh", "-c", "program1 | program2 | program3");
builder.start();

In some cases this unit might need to be terminated. However

process.destroy();

Will only destroy the "sh" command. The commands in the pipline will be orphaned and adopted by the init process.

Is there any way to easily terminate all these child processes – or execute a pipeline like the above in a way that makes it easier to terminate them . Altering progam 1/2/3 can't be done. Portability beyond linux is not a issue.

Best Answer

There's two ways I can think to do this:

You could run a pkill program1 program2 program3
You could write a intermediate program which launches the whole bash command line, this intermediate program would install a signal handler which kills it's own children when it gets a STOP signal.

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Java ProcessBuilder process.destroy() not killing child processes in winXP

I also think that emulating Ctrl-C in order to kill ssh entirely is problematic.

What I would do, is one of the following approaches. Either use windows commands to find out who are ssh's sons (which is a little bit problematic, since you need to know your current pid in order to recieve your own children-processes). I believe pstools of sysinternals is a good command-line tool that should enable you to track orphan processes. See this example for controlling windows processes either with taskList.exe (which can give you its output in CSV format BTW) or by executing a special VBScript.

The second approach is using a java library such as winp to execute and control the ssh process. I believe you'd be able to list all its children and forcibly kill them if sending the correct message would not suffice. This would be my preferred approach. Please note that the killRecursively method does exactly what you want.

Please note that those approaches should not render your application windows only. You can encapsulate those in a class that would run differently on Windows and linux machines.

Please note I didn't try to gain a fine-grained control on windows processes with, so I'm not sure how mature would those solutions I found are.

Java – ProcessBuilder: Forwarding stdout and stderr of started processes without blocking the main thread

Use ProcessBuilder.inheritIO, it sets the source and destination for subprocess standard I/O to be the same as those of the current Java process.

Process p = new ProcessBuilder().inheritIO().command("command1").start();

If Java 7 is not an option

public static void main(String[] args) throws Exception {
    Process p = Runtime.getRuntime().exec("cmd /c dir");
    inheritIO(p.getInputStream(), System.out);
    inheritIO(p.getErrorStream(), System.err);

}

private static void inheritIO(final InputStream src, final PrintStream dest) {
    new Thread(new Runnable() {
        public void run() {
            Scanner sc = new Scanner(src);
            while (sc.hasNextLine()) {
                dest.println(sc.nextLine());
            }
        }
    }).start();
}

Threads will die automatically when subprocess finishes, because src will EOF.

Best Answer

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Java ProcessBuilder process.destroy() not killing child processes in winXP

Java – ProcessBuilder: Forwarding stdout and stderr of started processes without blocking the main thread

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