Get PID of Runtime process using JNI

Question

I need to get the PID of a process which is launched via Java's Runtime.getRuntime().exec() command.

I know how to do it in JNA. But I really would like to do it with JNI and create my own libraries. Does anyone know how to do it?

import java.lang.reflect.Field;

class GetPid
{
    public native int getPid( long procHandle);

    static
    {
        System.loadLibrary("getpid");
    }

    public static void main(String args[])
    {
        try {

          Process process = Runtime.getRuntime().exec( "calc");
          Field f = process.getClass().getDeclaredField( "handle");
          f.setAccessible( true);
          long procHandle = f.getLong( process);

          System.out.println( "prochandle: " + procHandle + ", pid: " + new GetPid().getPid( procHandle));

        } catch( Exception e) {
          e.printStackTrace();
        }

    }
}

But what's the C part supposed to look like?

JNIEXPORT jint JNICALL
Java_GetPid_getPid(JNIEnv *env, jobject obj, jlong handle)
{
    ...

    return ???;
}

It would be great if someone could help me. I mainly seek the Windows solution, since you can get the PID for Linux from the Process field, but I wouldn't mind if someone could show me how to do this in Linux / Solaris as well.

Thank you very much in advance!

Answer 1

Got it. It was as simple as using:

#define WINVER 0x0501
#define _WIN32_WINNT 0x0501

and

JNIEXPORT jint JNICALL
Java_GetPid_getPid(JNIEnv *env, jobject obj, jlong handle)
{
  return GetProcessId((HANDLE) handle);
}

Thanks to all who tried to help :-)