launch1.launch

<launch>
    <!-- A Launch file is a `.launch` file (XML format) that can execute multiple commands by a single call -->
    <!-- More info about XML tags here: https://wiki.ros.org/roslaunch/XML -->

    <!-- Launch the rqt_console node -->
    <!-- More about <node> here: https://wiki.ros.org/roslaunch/XML/node -->
    <node pkg="rqt_console" type="rqt_console" name="rqt_console" required="true" />

    <!-- Load environment variables -->
    <!-- More about <env> here: https://wiki.ros.org/roslaunch/XML/env -->
    <env name="ROSCONSOLE_CONFIG_FILE" value="$(find cpp_basic_nodes)/config/launch1.config" />

    <!-- Create a group for publisher and subscriber -->
    <!-- More about <group> here: https://wiki.ros.org/roslaunch/XML/group -->
    <group ns="l1/ps">   <!-- ns: Napespace for all topics -->
        <!-- Launch the publisher node -->
        <node pkg="cpp_basic_nodes" type="launch1_publisher" name="cppl1_publisher" >
            <!-- Set publishing frequency to 0.5 Hz -->
            <!-- More about <param> here: https://wiki.ros.org/roslaunch/XML/param -->
            <param name="l1pub_PubFreq" value="0.5" type="double" />
            <!-- Remap (rename) the topic to the namespace 'l1/ps'-->
            <!-- More about <remap> here: https://wiki.ros.org/roslaunch/XML/remap -->
            <remap from="~/pub_topic" to="topic" /> <!-- The topic name will finally be /l1/ps/topic -->
        </node>
        <!-- Launch the Subscriber node -->
        <node pkg="cpp_basic_nodes" type="launch1_subscriber" name="cppl1_subscriber">
            <!-- Remap the topic name (to match the publisher topic name) -->
            <remap from="~/subs_topic" to="topic" /> <!-- Topic remapped to /l1/ps/topic -->
        </node>
    </group>

    <!-- Create a group for creating parameters in the launch -->
    <group ns="l1/params">
        <!-- Load parameters from a YAML file -->
        <!-- More about it here: https://wiki.ros.org/roslaunch/XML/param#Parameters_from_YAML_output -->
        <param name="set1" type="yaml" command="cat '$(find cpp_basic_nodes)/yaml/l1_params1.yaml'" />
        <!-- Launch the parameter scanning node -->
        <node pkg="cpp_basic_nodes" type="launch1_parameters" name="cppl1_parameters" />
    </group>

    <!-- Global parameters -->
    <!-- It is advisable to given them a name so that they do not shadow other parameters -->
    <param name="global" type="yaml" command="cat '$(find cpp_basic_nodes)/yaml/l1_params2.yaml'" />
</launch>