XACRO file code for XACRO tutorial in ROS

first_xacro.xacro

<?xml version="1.0"?>
<robot name="xacro_bot1" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <!-- Parameters -->
    <xacro:property name="a" value="0.2" />

    <!-- Links to be added -->
    <!-- Add a link -->
    <xacro:macro name="add_link" params="length name parent axis *origin">
        <!-- Physical link -->
        <link name="${name}_link">
            <visual>
                <origin xyz="0.0 0.0 ${length/2}"/>
                <geometry>
                    <box size="${a} ${a} ${length}"/>
                </geometry>    
            </visual>
            <material name="red">
                <color rgba="1.0 0.0 0.0 0.0"/>
            </material>
        </link>
        <!-- Joint between parent and link -->
        <joint name="${name}_joint" type="revolute">
            <xacro:insert_block name="origin" />
            <parent link="${parent}" />
            <child link="${name}_link" />
            <axis xyz="${axis}" />
            <limit lower="${-pi}" upper="${pi}" effort="30" velocity="10" />
        </joint>
    </xacro:macro>
    <!-- Base link -->
    <link name="base_link">
        <visual>
            <origin xyz="0 0 0.25" />
            <geometry>
                <box size="0.5 0.5 0.5" />
            </geometry>    
        </visual>
    </link>
    <!-- Link 1 -->
    <xacro:property name="l1_length" value="0.625" />
    <xacro:add_link name="l1" length="${l1_length}" parent="base_link" axis="0 1 0" >
        <origin xyz="0 0 0.5" rpy="0.0 0.0 0.0"/>
    </xacro:add_link>
    <!-- Link 2 -->
    <xacro:property name="l2_length" value="0.625" />
    <xacro:add_link name="l2" length="${l2_length}" parent="l1_link" axis="1 0 0">
        <origin xyz="0.0 0.0 ${l1_length}"/>
    </xacro:add_link>
    <!-- Link 3 -->
    <xacro:property name="l3_length" value="0.5" />
    <xacro:add_link name="l3" length="${l3_length}" parent="l2_link" axis="0 0 1" >
        <origin xyz="0.0 0.0 ${l2_length}"/>
    </xacro:add_link>
    <!-- Link 4 -->
    <xacro:property name="l4_length" value="1" />
    <xacro:add_link name="l4" length="${l4_length}" parent="l3_link" axis="1 0 0" >
        <origin xyz="0.0 0.0 ${l3_length}"/>
    </xacro:add_link>
    <!-- Link 5 -->
    <xacro:property name="l5_length" value="1" />
    <xacro:add_link name="l5" length="${l5_length}" parent="l4_link" axis="0 1 0" >
        <origin xyz="0.0 0.0 ${l4_length}"/>
    </xacro:add_link>
</robot>