rosversion <stack> | -d
The rosversion command prints version information for ROS stacks and can also print the name of the active ROS distribution.
rosversion takes in a single ROS stack name as an argument, or a -d option with no arguments to print the distribution version instead. If the version number for a stack is not known, "<unversioned>" will be printed instead.
Print codename for current ROS distribution.
2011, Willow Garage