本文讲如何用catkin创建一个ROS的package
1. catkin package的组成：一定要包含CMakeLists.txt及package.xml文件
my_package/ CMakeLists.txt package.xml
此外，每个package必须要有他自己的文件夹。
2. 推荐使用catkin workspace来处理catkin package
workspace_folder/ -- WORKSPACE
src/ -- SOURCE SPACE
CMakeLists.txt -- ‘Toplevel‘ CMake file, provided by catkin
package_1/
CMakeLists.txt -- CMakeLists.txt file for package_1
package.xml -- Package manifest for package_1
...
package_n/
CMakeLists.txt -- CMakeLists.txt file for package_n
package.xml -- Package manifest for package_n
3. 创建catkin package
使用catkin_create_pkg脚本来创建新的catkin package：
（1）切换source space目录至之前创建的catkin workspace
$ cd ~/catkin_ws/src
（2）用catkin_create_pkg创建一个catkin package，名字是beginner_tutorials，且依赖于已有的功能包std_msgs,roscpp,rospy，后者称为dependency
$ catkin_create_pkg beginner_tutorials std_msgs rospy roscpp
4. build 这个catkin workspace, source 这个setup文件
build方法：
$ cd ~/catkin_ws $ catkin_make
source方法：
$ . ~/catkin_ws/devel/setup.bash
5. package dependencies
（1）用rospack查看1阶dependencies：
$ rospack depends1 beginner_tutorials
package.xml中储存了package的dependencies信息
$ roscd beginner_tutorials $ cat package.xml
（2）用rospack查看间接（高阶）的dependencies：
$ rospack depends beginner_tutorials
6. customize（自定义、定制） package
6.1 自定义package.xml
(1) 描述标签（description tag）：尽可能短
5 <description>The beginner_tutorials package</description>
（2）Maintainer 标签：必须有，而且非常重要，至少要有一条。作用是让别人知道有关这个package该联系谁。
Toggle line numbers 7 <!-- One maintainer tag required, multiple allowed, one person per tag --> 8 <!-- Example: --> 9 <!-- <maintainer email="[email protected]">Jane Doe</maintainer> --> 10 <maintainer email="[email protected]">user</maintainer>
（3）许可证标签（license tag）：有很多开源许可证，我们这里使用BSD，因为许多ROS核心部件都是用的它。
12 <!-- One license tag required, multiple allowed, one license per tag --> 13 <!-- Commonly used license strings: --> 14 <!-- BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 --> 15 <license>TODO</license>
（4）dependencies标签： dependencies标签可分为build_depend, buildtool_depend, exec_depend, test_depend。因为我们使用了std_msgs, roscpp, and rospy，所以该标签应为：
27 <!-- The *_depend tags are used to specify dependencies --> 28 <!-- Dependencies can be catkin packages or system dependencies --> 29 <!-- Examples: --> 30 <!-- Use build_depend for packages you need at compile time: --> 31 <!-- <build_depend>genmsg</build_depend> --> 32 <!-- Use buildtool_depend for build tool packages: --> 33 <!-- <buildtool_depend>catkin</buildtool_depend> --> 34 <!-- Use exec_depend for packages you need at runtime: --> 35 <!-- <exec_depend>python-yaml</exec_depend> --> 36 <!-- Use test_depend for packages you need only for testing: --> 37 <!-- <test_depend>gtest</test_depend> --> 38 <buildtool_depend>catkin</buildtool_depend> 39 <build_depend>roscpp</build_depend> 40 <build_depend>rospy</build_depend> 41 <build_depend>std_msgs</build_depend>
我们希望在build和run的时候使用所有特定的dependencies，因此我们还要增加exec_depend标签，最后如下：
12 <buildtool_depend>catkin</buildtool_depend> 13 14 <build_depend>roscpp</build_depend> 15 <build_depend>rospy</build_depend> 16 <build_depend>std_msgs</build_depend> 17 18 <exec_depend>roscpp</exec_depend> 19 <exec_depend>rospy</exec_depend> 20 <exec_depend>std_msgs</exec_depend>
（5） 最终的package.xml：下面是不含有评论和未使用tag的package.xml文件，非常concise（简明）
<?xml version="1.0"?> <package format="2"> <name>beginner_tutorials</name> <version>0.1.0</version> <description>The beginner_tutorials package</description> <maintainer email="[email protected]">Your Name</maintainer> <license>BSD</license> <url type="website">http://wiki.ros.org/beginner_tutorials</url> <author email="[email protected]">Jane Doe</author> <buildtool_depend>catkin</buildtool_depend> <build_depend>roscpp</build_depend> <build_depend>rospy</build_depend> <build_depend>std_msgs</build_depend> <exec_depend>roscpp</exec_depend> <exec_depend>rospy</exec_depend> <exec_depend>std_msgs</exec_depend> </package>
6.2 自定义CMakeLists.txt