How to get versions in package.xml from roscpp codes

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Buried deep in the catkin documentation there is a note that after calling catkin_pacakge(), the package version is available as a cmake variable that is named after your package: <packagename>_VERSION

You could make this available to C++ code using the add_definitions cmake command, like:

catkin_package(
    # any arguments to catkin_package here
)

add_definitions("-D${PROJECT_NAME}_VERSION=\"${${PROJECT_NAME}_VERSION}\"")

This uses the -D option to the compiler, which is equivalent to a #define.

You could use the version in your code as a string, for example:

ROS_INFO("Package version is %s", mypackage_VERSION); // replace mypackage with your package name