publisher not publishing on topic

edit

im trying to publish a message on a topic once but it never publishes the data at all. This is the code in main

ros::init(argc, argv, "keeper_env");
   ros::NodeHandle n;
   ros::Publisher chatter_pub = n.advertise<std_msgs::Empty>("toggle_led", 1000);
   std_msgs::Empty msg;
   chatter_pub.publish(msg);

even putting it in a finite while loop dosent work

int i=0;
        ros::Rate rat(20);
    while(i<10)
    {   
        chatter_pub.publish(msg);
        ros::spinOnce();
        i++;
                rat.sleep();
    }

but if i put it in an infitite loop then it publishes the data.

while(ros::ok())
    {   
        chatter_pub.publish(msg);
        ros::spinOnce();

    }

If i put it in a if condition in that infinite loop then it still dosent publish. i dont want it to be called infintely. i just need it once. can someone please help me

int i=0;
while(ros::ok())
    {   

        if(i==0)
        {   
            printf("Doses it go iun here \n");
            chatter_pub.publish(msg);
            i++;
        }
        }