holding a twist message on cmd_vel node

edit

Hi again,

I have come up with some code that allows for a turtlebot 2, to go in a straight path for 5 seconds. My problem is that it sends the velocity command for a split fraction of time, Im not sure what it is. I am looking for a way to hold a published command on a topic for a period of time. What is the easiest way to hold a command on a topic for a certain period of time? I guess I'm looking for some command that is like; ros::topic.hold(time);

#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <time.h>
#include <iostream>

using namespace std;

int main(int argc, char** argv){

  ros::init(argc, argv, "gs_now");
  ros::NodeHandle nh;

  ros::Publisher pub = nh.advertise<geometry_msgs::Twist>(
    "/cmd_vel_mux/input/navi", 1);
  ros::Rate rate(1);  
  geometry_msgs::Twist vel;
  vel.angular.z = 0.0;
  vel.linear.x = 0.1;

  clock_t t, l;

  t = clock();

  while(ros::ok()){
     l = clock() - t;

     if( ((double)l / ((double)CLOCKS_PER_SEC)) == 1.000){
        pub.publish(vel);
        ROS_INFO_STREAM("Sending random velocity command:"
      << " linear=" << vel.linear.x
      << " angular=" << vel.angular.z
      << " at time =" << ((double)l / ((double)CLOCKS_PER_SEC)));
     }
     else if(((double)l / ((double)CLOCKS_PER_SEC)) == 2.000){
       pub.publish(vel);
       ROS_INFO_STREAM("Sending random velocity command:"
      << " linear=" << vel.linear.x
      << " angular=" << vel.angular.z
      << " at time =" << ((double)l / ((double)CLOCKS_PER_SEC)));
     }
     else if(((double)l / ((double)CLOCKS_PER_SEC)) == 3.000){
       pub.publish(vel);
       ROS_INFO_STREAM("Sending random velocity command:"
      << " linear=" << vel.linear.x
      << " angular=" << vel.angular.z
      << " at time =" << ((double)l / ((double)CLOCKS_PER_SEC)));
     }
     else if(((double)l / ((double)CLOCKS_PER_SEC)) == 4.000){
       pub.publish(vel);
       ROS_INFO_STREAM("Sending random velocity command:"
      << " linear=" << vel.linear.x
      << " angular=" << vel.angular.z
      << " at time =" << ((double)l / ((double)CLOCKS_PER_SEC)));
     }
    else if(((double)l / ((double)CLOCKS_PER_SEC)) == 5.000){
       ros::shutdown();
    }

       //rate.sleep();  
  }

}

Thank you.