Catkin creates and installs files for env-setting convenience. In the devel space there are setup.zsh and setup.bash, these contain variable zsh and bash specific tweaks. They both import setup.sh, which contains bourne-shell variable settings.
env.sh, pointed to by the CMake variable CATKIN_ENV is special; it executes its arguments in the environment created by setup.sh and returns. Any custom commands executed by CMake should do so via this script.
Environment hooks
Projects can, via the catkin_add_env_hooks() macro, add sh code to be executed by setup.sh (and by extension setup.bash and friends). If you need to add things to the environment, this is probably the place to do it. Don’t get fancy: the contents of these scripts must be interpretable by all members of the bourne shell family. Be safe and ensure that /bin/dash is okay with them.
You should avoid putting absolute paths into these environment hook ( at least in the install space). Instead use the variable $CATKIN_ENV_HOOK_WORKSPACE to point to workspace relative resources.
NOTE: These environment hooks are only for variable settings, shell aliases and functions.
