Fix #32 (CollectAgent should support running as daemon)

CollectAgent/collectagent.cpp

@@ -122,11 +122,12 @@ void mqttCallback(SimpleMQTTMessage *msg)
  * Print usage information
  */
 void usage() {
-  printf("Usage: collectagent [-l <host>] [-h <host>]\n");
+  printf("Usage: collectagent [-D] [-l <host>] [-h <host>]\n");
   printf("Collectagent will accept remote connections by listening to the\n");
   printf("specified listen address (-l <host>) at port 1883 (default MQTT port).\n");
   printf("It will also connect to cassandra to the specifiec addres (-h <host>).\n");
-  printf("The default <host> is localhost/127.0.0.1.\n\n");
+  printf("The default <host> is localhost/127.0.0.1.\n");
+  printf("If the -D option is specified, CollectAgent will run as daemon.\n\n");
 }
 
 int main(int argc, char* const argv[]) {
@@ -148,7 +149,7 @@ int main(int argc, char* const argv[]) {
       int ret;
       listenHost="localhost";
       cassandraHost="127.0.0.1";
-      while ((ret=getopt(argc, argv, "h:?"))!=-1) {
+      while ((ret=getopt(argc, argv, "h:l:D?"))!=-1) {
           switch(ret) {
               case 'h':
                   cassandraHost = optarg;
@@ -156,6 +157,9 @@ int main(int argc, char* const argv[]) {
               case 'l':
                   listenHost = optarg;
                   break;
+              case 'D':
+                  daemon(1,1);
+                  break;
               case '?':
               default:
                   usage();