ROs-Pcl question

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its a very basic question but i tried to read everything n now m confused. "i am totally new at ros and pcl though". we are working with a project robot object detection and analysis. so far in our project we can subscribed to pointcloud. but the question is how to stored it in pcd file or is there any better solution for that?? and how to use pcl for that ??

any help would be appreciated! thank you