Killing processes from java

I have created a Java application that can start processes and capture their PIDs so that the application can monitor the process. The user may later choose to kill the whole process tree (session). I have done this by utilizing setsid. One scenario is starting a whole bunch of different processes via a shell script by: setsid . The PID represents the new session and killing it will kill all processes spawned in that session. It worked great until Ubuntu 12.10 was released. Now i cannot kill all sessions started via setsid. One example is Firefox and Google Earth. Gedit can still be killed if started through setsid. I created a simple test program that perform kill -SIGTERM -PID . The test program manages to kill firefox started via setsid under Ubuntu 12.04 but not under Ubuntu 12.10. I don’t know what has changed. I have executed the program in both distributions using OpenJDK 6, 7 and Oracle JDK 6.

 public class kill < public static void main(String[] args) < try < System.out.println("kill -SIGTERM -" + args[0]); Process proc = Runtime.getRuntime().exec("kill -SIGTERM -" + args[0]); int exitVal = proc.waitFor(); System.out.println("Exit value: " + exitVal); // often 1 under Ubuntu 12.10 >catch (Exception e) < >>

After som testing I’ve found that on Ubuntu 12.10 it’s possible to kill the process group if a signal isn’t specified, e.g: kill — —

To clarify, kill -SIGTERM — works in the bash shell in Ubuntu 12.10 but not if executed through Runtime.getRuntime.exec(), one qould have to remove the ‘SIG’ part as described above 🙂

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How to find and kill running win-processes from within java?

It is often necessary to kill running Windows processes from within a Java program, for example, to clean up resources or to terminate processes that are no longer needed. However, it is important to ensure that the correct process is killed, as killing an essential process can cause system instability or data loss. In this article, we will discuss different methods for finding and killing Windows processes from within a Java program.

Method 1: Using the Windows Task Manager

To find and kill running Win-Processes from within Java using the Windows Task Manager, you can use the following steps:

Process process = Runtime.getRuntime().exec("tasklist");

BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream())); String line; StringBuilder sb = new StringBuilder(); while ((line = reader.readLine()) != null)  sb.append(line).append(System.lineSeparator()); > String taskListOutput = sb.toString();

String processName = "notepad.exe"; // Replace with the name of the process you want to kill String pidRegex = "^" + processName + "\\s+(\\d+)"; Pattern pattern = Pattern.compile(pidRegex, Pattern.MULTILINE); Matcher matcher = pattern.matcher(taskListOutput); if (matcher.find())  String pid = matcher.group(1); // Kill the process using the PID >

Use the Runtime class to execute the taskkill command with the PID of the process you want to kill.

Process killProcess = Runtime.getRuntime().exec("taskkill /F /PID " + pid);

import java.io.BufferedReader; import java.io.InputStreamReader; import java.util.regex.Matcher; import java.util.regex.Pattern; public class WindowsTaskManager  public static void main(String[] args) throws Exception  String processName = "notepad.exe"; // Replace with the name of the process you want to kill Process taskListProcess = Runtime.getRuntime().exec("tasklist"); BufferedReader reader = new BufferedReader(new InputStreamReader(taskListProcess.getInputStream())); String line; StringBuilder sb = new StringBuilder(); while ((line = reader.readLine()) != null)  sb.append(line).append(System.lineSeparator()); > String taskListOutput = sb.toString(); String pidRegex = "^" + processName + "\\s+(\\d+)"; Pattern pattern = Pattern.compile(pidRegex, Pattern.MULTILINE); Matcher matcher = pattern.matcher(taskListOutput); if (matcher.find())  String pid = matcher.group(1); Process killProcess = Runtime.getRuntime().exec("taskkill /F /PID " + pid); > > >

Method 2: Using the Windows Command Line

To find and kill running Win-Processes from within Java using the Windows Command Line, you can use the following steps:

Create a ProcessBuilder object to execute the Windows command line process.
Set the command to execute as «tasklist» to get the list of running processes.
Redirect the output of the command to a file using the «>» operator.
Read the file to get the list of running processes.
Set the command to execute as «taskkill» to kill the desired process.
Pass the process ID as a parameter to the «taskkill» command.

Here’s an example code snippet that demonstrates the above steps:

import java.io.*; public class ProcessKiller  public static void main(String[] args) throws IOException  String processName = "notepad.exe"; // replace with the name of the process to kill ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", "tasklist > processes.txt"); builder.redirectErrorStream(true); Process process = builder.start(); try  process.waitFor(); > catch (InterruptedException e)  e.printStackTrace(); > File file = new File("processes.txt"); BufferedReader reader = new BufferedReader(new FileReader(file)); String line; while ((line = reader.readLine()) != null)  if (line.contains(processName))  String[] parts = line.split("\\s+"); String pid = parts[1]; ProcessBuilder builder2 = new ProcessBuilder("cmd.exe", "/c", "taskkill /f /pid " + pid); builder2.redirectErrorStream(true); Process process2 = builder2.start(); try  process2.waitFor(); > catch (InterruptedException e)  e.printStackTrace(); > > > reader.close(); > >

This code first executes the «tasklist» command and redirects the output to a file named «processes.txt». It then reads the file to find the process ID of the process to kill and executes the «taskkill» command with the process ID as a parameter to kill the process.

Note that the code uses the «/f» option with the «taskkill» command to force the process to terminate. This should be used with caution as it may cause data loss or corruption.

Method 3: Using the Java Process API

To find and kill running Win-Processes from within Java using the Java Process API, you can follow these steps:

Use the Runtime.getRuntime().exec() method to execute the tasklist command to get a list of running processes.

Process process = Runtime.getRuntime().exec("tasklist");

BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream())); String line; while ((line = reader.readLine()) != null)  // process the output >

String[] parts = line.trim().split("\\s+"); String name = parts[0]; int pid = Integer.parseInt(parts[1]);

Use the Runtime.getRuntime().exec() method to execute the taskkill command to kill a process by its ID.

Runtime.getRuntime().exec("taskkill /F /PID " + pid);

Putting it all together, here’s an example code:

import java.io.BufferedReader; import java.io.InputStreamReader; public class ProcessKiller  public static void main(String[] args) throws Exception  Process process = Runtime.getRuntime().exec("tasklist"); BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream())); String line; while ((line = reader.readLine()) != null)  String[] parts = line.trim().split("\\s+"); String name = parts[0]; int pid = Integer.parseInt(parts[1]); if (name.equals("notepad.exe"))  Runtime.getRuntime().exec("taskkill /F /PID " + pid); > > > >

This code will kill all running instances of Notepad. Note that you should replace notepad.exe with the name of the process you want to kill. Also note that the /F option is used to force the process to terminate.

Method 4: Using a Third-Party Library

To find and kill running Win-Processes from within Java, we can use a third-party library called jna-platform . This library provides a platform-independent way to access native code from Java. Here are the steps to use this library:

Add jna-platform library to your project. You can download it from here.
Import the necessary classes from the library:

import com.sun.jna.platform.win32.Kernel32; import com.sun.jna.platform.win32.WinDef; import com.sun.jna.platform.win32.WinNT;

public static int findProcessId(String processName)  WinNT.HANDLE snapshot = Kernel32.INSTANCE.CreateToolhelp32Snapshot(Kernel32.TH32CS_SNAPPROCESS, new WinDef.DWORD(0)); try  Win32.PROCESSENTRY32.ByReference entry = new Win32.PROCESSENTRY32.ByReference(); while (Kernel32.INSTANCE.Process32Next(snapshot, entry))  if (Native.toString(entry.szExeFile).equalsIgnoreCase(processName))  return entry.th32ProcessID.intValue(); > > > finally  Kernel32.INSTANCE.CloseHandle(snapshot); > return 0; >

This code uses the CreateToolhelp32Snapshot function to create a snapshot of the current processes in the system. Then it loops through the list of processes and checks if the name of the process matches the given processName . If it finds a match, it returns the process ID.

public static void killProcess(int pid)  WinNT.HANDLE process = Kernel32.INSTANCE.OpenProcess(WinNT.PROCESS_TERMINATE, false, pid); Kernel32.INSTANCE.TerminateProcess(process, 0); Kernel32.INSTANCE.CloseHandle(process); >

This code uses the OpenProcess function to open a handle to the process with the given pid . Then it calls the TerminateProcess function to terminate the process. Finally, it closes the handle to the process.

int pid = findProcessId("notepad.exe"); if (pid != 0)  killProcess(pid); >

This code finds the process ID of the running notepad.exe process and kills it.

That’s it! Using the jna-platform library, we can easily find and kill running Win-Processes from within Java.

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The right way to kill a process in Java

If the process you want to kill has been started by your application

Then you probably have a reference to it ( ProcessBuilder.start() or Runtime.exec() both return a reference). In this case, you can simply call p.destroy() . I think this is the cleanest way (but be careful: sub-processes started by p may stay alive, check Process.destroy does not kill multiple child processes for more info).

The destroyForcibly should only be used if destroy() failed after a certain timeout. In a nutshell

terminate process with destroy()
allow process to exit gracefully with reasonable timeout
kill it with destroyForcibly() if process is still alive

If the process you want to kill is external

Then you don’t have much choice: you need to pass through the OS API ( Runtime.exec ). On Windows, the program to call will be taskkill.exe , while on Mac and Linux you can try kill .

Have a look at Support for Process.destroyForcibly() and .isAlive() from Java 8 and Killing a process using Java and Code a Simple Java App to Kill Any Process After a Specified Time for more info.

If you’re trying to kill the main process your java code started, I’d suggest using System.exit() . The benefits are explained here: when should we call system exit in java.

Essentially, System.exit() will run shutdown hooks that will make sure any dependent non-daemon processes that may not have completed their work are killed before your process is killed. This is the clean way to do it.

If the process is not yours, you will have to rely on the Operating System to do this work for you as explained in this answer: Killing a Process Using Java

In that case your suggestion of Runtime.exec() a kill on *nix would be a decent way to go.

Now as for destroyForcibly() , you’re typically going to call that on a child process spawned by your java code that was presumably started with the process api’s ProcessBuilder.start() or Runtime.exec()

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Killing processes from java