Process Builder and Process in Java - how to execute a process with a timeout :? [duplicate]

Question

I need to execute an external batch file in java with a specific timeout. which means that if the batch execution take longer than specified timeout, i need to cancel the execution.

here is a sample code that i wrote:

public static void main(String[] args) throws IOException, InterruptedException {
    ProcessBuilder p = new ProcessBuilder("c:\\wait.bat", "25");  // batch file execution will take 25 seconds.
    final long l = System.currentTimeMillis();
    System.out.println("starting..." + (System.currentTimeMillis() - l));
    final Process command = p.start();
    System.out.println("started..." + (System.currentTimeMillis() - l));

    Timer t = new Timer();
    t.schedule(new TimerTask() {

        @Override
        public void run() {
            command.destroy();
        }
    }, 5000);   // it will kill the process after 5 seconds (if it's not finished yet).
    int i = command.waitFor();
    t.cancel();
    System.out.println("done..." + (System.currentTimeMillis() - l));
    System.out.println("result : " + i);

    System.out.println("Really Done..." + (System.currentTimeMillis() - l));
}

the batch file "wait.bat" is something like this:

@echo off
echo starting the process...
@ping 127.0.0.1 -n 2 -w 1000 > nul
@ping 127.0.0.1 -n %1% -w 1000> nul
echo process finished succesfully
@echo on

As you see in the code, batch file will take 25 seconds to finish (first line in main method) and the Timer will destroy the command after 5 seconds.

here is the output of my code:

starting...0
started...0
done...5000
result : 1
Really Done...5000
BUILD SUCCESSFUL (total time: 25 seconds)

as you see in output, the last line ("Really Done...") is executed in 5th second but the application is finished after 25 seconds.

my question is that : even though i called the destroy method in my timer, why jvm still waiting for the process to be finished ?

Answer 1

If you use Unix/Linux, then write a wrapper bash shell script to interrupt an external command by timeout, then call the wrapper from Java.

The wrapper script looks like

#!/bin/bash
timeout 60 <your command>

You can detect if timeout expired by checking the script exit code which is 124 in case of timeout

See

man timeout

Answer 2

I could be a problem with the cancel method of the timer. try to start the timer as daemon thread.

Timer t = new Timer(true);