Merge pull request firecracker-microvm#102 from superfly/expose-pid

Expose machine's PID

machine.go

@@ -163,6 +163,19 @@ func (m *Machine) Logger() *log.Entry {
 	return m.logger.WithField("subsystem", userAgent)
 }
 
+// PID returns the machine's running process PID or an error if not running
+func (m *Machine) PID() (int, error) {
+	if m.cmd == nil || m.cmd.Process == nil {
+		return 0, fmt.Errorf("machine is not running")
+	}
+	select {
+	case <-m.exitCh:
+		return 0, fmt.Errorf("machine process has exited")
+	default:
+	}
+	return m.cmd.Process.Pid, nil
+}
+
 // NetworkInterface represents a Firecracker microVM's network interface.
 type NetworkInterface struct {
 	// MacAddress defines the MAC address that should be assigned to the network