How do I find the process ID (pid) of a process started in java?

Question

If I get a process object in Java through Runtime.getRuntime().exec(...), or ProcessBuilder.start(), I can wait for it through Process.waitFor(), which is like Thread.join(), or I could kill it with Process.destroy(), which is like the deprecated Thread.stop().

BUT: How do I find the pid of the Process Object? I don't see a method for doing that in The Official Documentation. Can I do this in Java? If so, how?

Solution 1

This guy calls out to bash to get the PID. I'm not sure if there is an java solution to the problem.

/**
 * Gets a string representing the pid of this program - Java VM
 */
public static String getPid() throws IOException,InterruptedException {

  Vector<String> commands=new Vector<String>();
  commands.add("/bin/bash");
  commands.add("-c");
  commands.add("echo $PPID");
  ProcessBuilder pb=new ProcessBuilder(commands);

  Process pr=pb.start();
  pr.waitFor();
  if (pr.exitValue()==0) {
    BufferedReader outReader=new BufferedReader(new InputStreamReader(pr.getInputStream()));
    return outReader.readLine().trim();
  } else {
    System.out.println("Error while getting PID");
    return "";
  }
}

Source: http://www.coderanch.com/t/109334/Linux-UNIX/UNIX-process-ID-java-program

Solution 2

Similar to the other tools mentioned, there is the jps command line tool that comes with the Java runtime. It spits out the PIDs of all running JVMs. The benefit is the output one needs to parse is confined to only the JVM processes.

Comments

[Mike Baranczak]

Another benefit: it's cross-platform, unlike tasklist.

[Leo Izen]

You are assuming I'm on Windows, which I'm not.

[splashout]

I think this will give the pid of the JVM process... not the process spawned by Java which I believe is what the question is asking.

[nsfyn55]

I think you need to read a bit closer. It spawns a process thats only job is to echo its own PID to its stdout which itself is piping to the stdin file descriptor associated with the JVM.

[user924272]

Vectors are old-hat, and is synchronized - no real need to use that type of collection - try using an ArrayList instead. Just saying.

[nsfyn55]

Just saying what? This is not germane to the problem. The question is about accessing a PID not java best practices.