See Especially
Overview
The rosbag package provides a command-line tool for working with bags as well as code APIs for reading/writing bags in C++ and Python.
To find out more about the rosbag command-line tool, see rosbag Command-line Usage and Cookbook examples
rosbag has code APIs for reading and writing bags in either C++ or Python. For a description of these APIs, see rosbag Code API
For technical details on the contents of bag files, see Bag file format
Outside of rosbag package, from groovy there's a gui client rqt_bag.
Overview in addition:
Stability
The rosbag command-line tool and code APIs are stable. Every effort will be made to maintain backwards compatibility.
The main new feature being planned for rosbag is the addition of a ROS API for interacting with the playing and recording nodes via service calls.