rosdep 來下載並安裝依賴項

Usage: rosdep [options] <command> <args>
Commands:
rosdep check <stacks-and-packages>...
        check if the dependencies of package(s) have been met.
rosdep install <stacks-and-packages>...
        generate a bash script and then execute it.
rosdep db
        generate the dependency database and print it to the console.
rosdep init

        initialize rosdep sources in /etc/ros/rosdep.  May require sudo.
rosdep keys <stacks-and-packages>...
        list the rosdep keys that the packages depend on.
rosdep resolve <rosdeps>
        resolve <rosdeps> to system dependencies
rosdep update
        update the local rosdep database based on the rosdep sources.
rosdep what-needs <rosdeps>...
        print a list of packages that declare a rosdep on (at least one of) <rosdeps>
rosdep where-defined <rosdeps>...
        print a list of yaml files that declare a rosdep on (at least one of) <rosdeps>
rosdep fix-permissions
        Recursively change the permissions of the user's ros home directory.
        May require sudo.  Can be useful to fix permissions after calling "rosdep update" with sudo accidentally.

例程：

        為 turtlesim 下載並安裝系統依賴項。
        $ rosdep install turtlesim