We can save the point cloud to a PCD (Point Cloud Data) file by using the following code. The file name is pcl_write.cpp inside the src folder.

#include <ros/ros.h> 
#include <pcl/point_cloud.h> 
#include <pcl_conversions/pcl_conversions.h> 
#include <sensor_msgs/PointCloud2.h> 
//Header file for writing PCD file 
#include <pcl/io/pcd_io.h> 
 
void cloudCB(const sensor_msgs::PointCloud2 &input) 
{ 
    pcl::PointCloud<pcl::PointXYZ> cloud; 
    pcl::fromROSMsg(input, cloud); 
 
//Save data as test.pcd file 
    pcl::io::savePCDFileASCII ("test.pcd", cloud); 
} 
 
main (int argc, char **argv) 
{ 
    ros::init (argc, argv, "pcl_write"); 
 
    ROS_INFO("Started PCL write node"); 
 
    ros::NodeHandle nh; 
    ros::Subscriber bat_sub = nh.subscribe("pcl_output", 10, cloudCB); 
 
    ros::spin(); 
 
    return 0; 
}