Colcon

In ROS2

Before we build, we should source the underlay first, which is the ros humble setup.zsh file

In the root of the workspace, run colcon build.

colcon build --symlink-install
colcon build --packages-up-to
colcon build --event-handlers console_direct+
# --symlink-install allow the installed files to be changed by changing the files in the source space without build again.(e.g. python files or other non-compiled resources, except c++)
# --packages-up-to: builds thie package you want, plus all its dependencies, but not the whole workspace(save time)
# --event-handlers console_direct+ shows console output while building

run test for the packages just built, run
```
colcon test
```
when colcon has completed building successfully, the outpt will be in the install directory. We need to source all required elements to our path before we we can use any of the installed executables or libraries. run
```
source install/setup.zsh
```

after all steps above, we can run some nodes

ros2 run xxx_subscriber subscriber_function
ros2 run xxx_publisher publisher_function

If you do not want to build a specific package place an empty file named COLCON_IGNORE in the directory

build python package

write source code
change setup.py: create command tools, install python library
change package.xml: define ros2 dependency like rclpy, std_msgs, tell colcon build type
setup.cfg: set installation path