CODEWITHSUNDEEP
javaruntime.exec
devashish jasani
devashish jasani

Reputation: 413

In java determine if a process created using Runtime environment has finished execution?

Runtime.getRuntime.exex("abc.exe -parameters");

using .waitFor() does not help to determine the completion of process.

Upvotes: 6

Views: 15235

Answers (4)

Stephen C
Stephen C

Reputation: 718708

Process.waitFor() (javadoc) should work. If it doesn't work then either:

  • there's a bug in the JVM or the OS (highly unlikely for something like this), or

  • there is something about the process and/or your Java code that means that the process won't exit.

In current releases of Java you can also use Process.isAlive (javadoc) to test the process status without blocking until it finishes. For Java 7 and older there is a hacky solution that entails polling the process return code and catching an exception, but this is inefficient. You should upgrade to Java 8 or later as soon as possible!

Once the task is finished its goes for an indefinite wait. (I don't know why).

If this happening, then neither waitFor() or isAlive() will help.

The most likely reasons that a process launched from Java won't / can't exit are:

  • the process is blocked waiting for your Java application to give it some input (via its stdin),

  • the process is blocked waiting for your Java application to read its output (i.e. its stdout or stderr),

  • it is blocked waiting on some external event; e.g. if it is trying to talk remote server that is not responding,

  • something has sent it a STOP signal of some kind, or

  • it is just taking a looong time to run.

The first two of these reasons / causes can be addressed by (respectively) closing the Java output stream connected to its standard input, and reading (and possibly discarding) the Java input streams connected to its standard output and standard error. The other causes are intractable, and your only options are to "wait it out" or attempt to kill off the process.

Bottom line - you need to find out why your process isn't completing. The blocked Process.waitFor() call is a symptom, not the disease.

Upvotes: 10

Essej
Essej

Reputation: 861

I have a similar issue and neither of the methods written here works for me. This is my code:

public void startCCleaner() {
    System.out.println("Starting ccleaner...");
    try {
        Process process = new ProcessBuilder("C:\\Program Files\\CCleaner\\CCleaner64.exe").start();
        if(process.waitFor() == 0 ){
            System.out.println("Process terminated ");
        }
    } catch (IOException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

Upvotes: 1

ericsoco
ericsoco

Reputation: 26253

Looks like JDK8 introduces Process.isAlive(). Surprised it took so long...

In the meantime, the best option seems to be to poll Process.exitValue(), wrapped in a try-catch:

// somewhere previous...
String[] cmd = { "abc.exe", "-p1", "-p2" };
Process process = Runtime.getRuntime.exec(cmd);

// call this method repeatedly until it returns true
private boolean processIsTerminated () {
    try {
        process.exitValue();
    } catch (IllegalThreadStateException itse) {
        return false;
    }
    return true;
}

Alternately, a similar method could return the exit value if the process had terminated, or some other specified value if not.

Upvotes: 18

Hunter McMillen
Hunter McMillen

Reputation: 61515

If you don't want to use waitFor(), which apparently you don't you can always test the exit value directly. 

import java.util.*;
import java.io.*;
public class ProcExitTest
{
    public static void main(String args[])
    {
        try
        {            
            Runtime rt = Runtime.getRuntime();
            Process proc = rt.exec("<....>");
            int exitVal = proc.exitValue();
            System.out.println("Process exitValue: " + exitVal);
        } 
          catch (InterruptedException ie)
          {
            ie.printStackTrace();
          }
    }
}

exit code 0 means normal termination.

Upvotes: 0

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