ros2 remapping launch file

This means mimic will subscribe to /turtlesim1/sims pose topic and republish it for /turtlesim2/sims velocity command topic to subscribe to. The package providing this framework is launch_ros, which uses the non-ROS-specific launch framework underneath. It also ensures that all launch file formats are recognized. The string __ns can be given on the match part of a rule to signal a change of the default namespace. The structure i have been using is: Or else in this case you can copy the contents of .launch file in another file and remap it there itself. Example of topic/service remapping order: Example of node/namespace remapping order: Example of a default and node specific namespace remap: The following sections explain how the syntax enables the use cases above. As it was the case in ROS 1, ROS 2 nodes allow configuration via command line arguments to a certain degree. Remapping rules are applied in the following order: Within each category, the rules are applied in the order in which the user gave them. The basename is the last token in a name. Using Python, XML, and YAML for ROS 2 Launch Files, ros2 launch , [INFO] [launch]: Default logging verbosity is set to INFO, [INFO] [turtlesim_node-1]: process started with pid [11714], [INFO] [turtlesim_node-2]: process started with pid [11715], [INFO] [mimic-3]: process started with pid [11716], ros2 topic pub -r 1 /turtlesim1/turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: -1.8}}", ROS 2 Iron Irwini (codename iron; May, 2023), Writing a simple publisher and subscriber (C++), Writing a simple publisher and subscriber (Python), Writing a simple service and client (C++), Writing a simple service and client (Python), Writing an action server and client (C++), Writing an action server and client (Python), Composing multiple nodes in a single process, Integrating launch files into ROS 2 packages, Running Tests in ROS 2 from the Command Line, Building a visual robot model from scratch, Using Fast DDS Discovery Server as discovery protocol [community-contributed], Unlocking the potential of Fast DDS middleware [community-contributed], Using quality-of-service settings for lossy networks, Setting up efficient intra-process communication, Creating a content filtering subscription, Deploying on IBM Cloud Kubernetes [community-contributed], Building a real-time Linux kernel [community-contributed], Migrating launch files from ROS 1 to ROS 2, Using ROS 2 launch to launch composable nodes, Migrating YAML parameter files from ROS 1 to ROS 2, Passing ROS arguments to nodes via the command-line, Synchronous vs. asynchronous service clients, Working with multiple ROS 2 middleware implementations, Running ROS 2 nodes in Docker [community-contributed], Visualizing ROS 2 data with Foxglove Studio, Building ROS 2 with tracing instrumentation, On the mixing of ament and catkin (catment), ROS 2 Technical Steering Committee Charter. When a name is to be tested the substitution operators (~ and {}) in the name and in the rule are replaced with the content they stand for. The "topic1" won't be here anymore, instead you'll get the messages from "topic2". Launch files simplify running complex systems with many nodes and specific configuration details. . This tutorial uses the rqt_graph and turtlesim packages. In ROS1 launch files were implemented in XML. In exchange, it makes argument extraction slightly more difficult as all options must be known ahead of time, whereas --ros-args-based namespacing can achieve the same with a couple rules. As an example, to pass some_log.config configuration file to some_ros_executable, one may execute: Logging to rosout, stdout and an external logging library can be independently enabled or disabled. Remapping rules may be introduced using the --remap/-r option. Command line argument extraction happens within rcl. This keeps the command line verbosity at a minimum and avoids the need for flags, but is error prone. Because remapping needs to capture text to use during replacement, the C function fnmatch() cannot be used as the implementation. Tasks 1 Setup Create a new directory to store your launch files: mkdir launch 2 Write the launch file Let's put together a ROS 2 launch file using the turtlesim package and its executables. Remapping rules have two parts. The design document details the goal of the design of ROS 2's launch system (not all functionality is currently available). This is a feature of ROS 1 remapping. I have tried it with a simple example and having the remap tag before the node tag is the correct way: Are you sure your teleop node actually has that topic? Because the user will see the name after it has been remapped by static rules, dynamic rules should be applied after static ones. Prerequisites. A user can supply node specific remapping arguments via the command line. import os from ament_index_python.packages import get_package_share_directory from launch import LaunchDescription from launch_ros.actions import Node def generate_launch_description(): ld = LaunchDescription() config = os.path.join . This character may still be difficult on other shells, like zsh. a ROS client library like rclcpp, arguments unknown to rcl are left unparsed but accessible by these layers, which in turn can continue parsing or eventually warn the user if unknown arguments remain. If you have control over the launch file you can use an argument to allow passing in a different name for the node name. in a single file, that you can launch with only one command line. For example **/bar:=/bar/\1 matches the name /foo/bar with ** capturing /foo, but the new name is /bar/foo. replacement says what the new name will be. The output of rosnode list is /rosout /turtlebot_teleop_keyboard arp ( Dec 4 '14 ) Two turtlesim windows will open, and you will see the following [INFO] messages telling you which nodes your launch file has started: To see the system in action, open a new terminal and run the ros2 topic pub command on the /turtlesim1/turtle1/cmd_vel topic to get the first turtle moving: You will see both turtles following the same path. To re-use other packages in the ROS2 ecosystem, it's often advantageous to directly re-use the launch files provided with a package by using IncludeLaunchDescription. Here the syntax is the same, and additionally it can be prefixed with a nodes current name. Topics, parameters, and services are identified by Names. ros2 run some_package some_ros_executable --ros-args --remap foo:=bar or its shorter equivalent: ros2 run some_package some_ros_executable --ros-args -r foo:=bar As is, this remapping rule applies to each and every node that some_ros_executable spawns unless explicitly ignored in code. All private names are expanded to the new name before any remapping rules are applied to them. Remapping rules have two parts. The output of rosnode list is. The strings between slashes are called tokens. ; You have already created a ROS 2 workspace.The name of our workspace is "dev_ws", which stands for "development workspace." I am using hydro on Ubuntu 12.04. := for parameter assignment and ~= for name remapping. If no user defined arguments are provided after ROS specific arguments are, the double dash token (--) may be elided: Note that a sole trailing --ros-args remains a valid invocation. Flags, in contrast with other custom syntax alternatives, are: Unfortunately, since these flags coexist with user-defined ones, additional guarding and extraction devices must be put in place one of the reasons why these were avoided entirely in ROS 1 command lines. will set the parameter string_param on nodes named some_node in any namespace. These use cases are being considered for remapping in ROS 2: This is the ability to apply remap rules to one node in a process without affecting the other nodes. And, to make sure the ROS launch file can find the code, we have to make sure we change the permissions of the Python script before we execute the launch file. This could be useful when two different names expand to the same FQN. Hi, Just to clarify. The replacement side must have a FQN with no special operators. Does that mean I can't rename nodes? External logging may be configured using the --log-config-file option. match tests if a name should be remapped. Matching works on FQN only. The character for the wild card * was chosen to match fnmatch. ROS2 BASICS IN 5 DAYS. A remap rule consists of two names: one that should be replaced with another. For example */bar **/* ~/* are allowed, but *bar *** ~* are invalid. It should be read before reading this article. Instead, you can use a so-called launch file. Here is a launch file I am using. This is a proposal for the ROS 2 remapping rule syntax. Its possible a user may want to change multiple instances of a basename to another token. This option takes a single string value assignment statement, where value is a fully qualified enclave path used to locate the respective security artifacts within the configured keystore. As mentioned above, this can either be in Python, XML, or YAML. This should be changeable without affecting FQN. A hidden node (the ros2 topic pub command you ran) is publishing data to the /turtlesim1/turtle1/cmd_vel topic on the left, which the /turtlesim1/sim node is subscribed to. Dynamic remapping is the ability to remap a name while a node is running. This option takes a single name:=value assignment statement, where value is in YAML format and thus YAML type inference rules apply. ROS 1 remapping works on Fully Qualified Names (FQN). If you write this instead: <launch> The rest of the graph shows what was described earlier: mimic is subscribed to /turtlesim1/sims pose topic, and publishes to /turtlesim2/sims velocity command topic. However, usually remapping is done on the subscribing node, meaning that it is actually subscribing to the remapped topic. It means relative names are first expanded to FQN, and then processed as during exact FQN replacement. Nodes are said to be in a namespace or have a default namespace. This is also part of ROS 1 remapping. *bar looks like it would match foobar, but that would mean matching a partial token. While the system is still running, open a new terminal and run rqt_graph to get a better idea of the relationship between the nodes in your launch file. With unique namespaces, messages meant for different turtles can be distinguished. For packages with launch files, it is a good idea to add an exec_depend dependency on the ros2launch package in your packages package.xml: This helps make sure that the ros2 launch command is available after building your package. Is it possible?? Except where otherwise noted, these design documents are licensed under Creative Commons Attribution 3.0. This node has added configuration details in the form of remappings. These references are required to be separated from tokens by a /. The first part is used to determine if the rule applies to a name. MoveIt! On the match side it may be used by itself or with a nodename: prefix. To limit it to some_node, one may execute: The namespace is everything prior to the basename. Because of this, increasingly precise addressing mechanisms as well as leading double underscores (__) in some positional arguments, both natural extensions of existing ROS 1 command line features, are combined with ROS 2 specific command line flags. The node name is used in log messages and to create private names. With a launch file you can write all the nodes with a complete configuration (remapping, parameters, etc.) Note that YAML type inference rules for parameter values apply. URDF . Except where otherwise noted, these design documents are licensed under Creative Commons Attribution 3.0. They may not be prefixed to a node name or namespace replacement rule (__name, __node, or __ns). * matches a single token delimeted by slashes (/). Finally the name is replaced with the replacement. ** behaves similar to its use in bash>=4.0 with the globstar option set. I'd like to use something like we do in ROS1: If a logging level is specified more than once in the passed command line arguments, the last one prevails. This syntax is identical to ROS 1. The first part is used to determine if the rule applies to a name. It may be useful for a developer who has started a node and wants to connect it to a different source. This also isnt a true remapping rule, but the syntax is similar. In other words, turtlesim2 will mimic turtlesim1s movements. Turtlebot_bringup[WARN]Create : robot not connected yet, sci not available, Cannot launch turtlebot dashboard [closed], Are there any turtlebot ROS apps for ios ? ros2launchpythonyamlxml.launch.xml ros1ros noderos nodeletros2component launch.py component; Python Launch. Remaining arguments can still be accessed by the user via rcl API. These import statements pull in some Python launch modules. You will also need to use a text editor of your preference. It is possible a token is used throughout an interface, but is undesirable to the end user. link Comments It still does not work. The match part of a rule uses these operators: The operators * and ** are similar to the globbing behavior in bash. Can I change the node-name "talker" to "speaker"?? As a quick summary of ROS command line capabilities: For name remapping and parameter assignment, specific nodes can be targeted by prepending the option value with the node name followed by a colon :, as in --remap my_node:from:=to and --param my_node:name:=value. This article describes ROS 2 nodes command line arguments and their syntax. Names are conceptually divided into two pieces: namespace and basename. This means it should be possible to make a rule that replaces all uses of this token. Doing so requires matching prior to FQN expansion. Other URL schemes, specific to each interface type e.g. Static remapping is giving a node remapping rules at the time it is launched. When an instance of the --ros-args flag is found in argv, until either a double dash token (--) is found or the end of the argument array is reached, all arguments that follow are taken as ROS specific arguments to be parsed as such. However, to support ROS specific arguments that target upper ROS layers e.g. $ ros2 launch . It is also responsible for monitoring the state of the processes launched, and reporting and/or reacting to changes in the state of those processes. Remapping applies to the lines following the remap. This is part of the behavior of ROS 1 remapping, so it has proven useful and including it will ease the transition to ROS 2. Assuming the nodes name is unique in a process, a rule can be prefixed with the name of the target node and a :. The syntax here can be passed to a node via the command line. Enclave assignment may be achieved using the --enclave/-e option. This option takes a single configuration file, whose format depends on the actual external logging library being used. In the example where you remap the topic from chatter to foobar, the node is of type talker and it's name is "talker". Remapping rules are the instructions describing how a node should change the names it uses. The wildcard ** is useful because it matches every possible namespace when combined with a slash. This is the ability to match a name by how it is used in code. As an example, to assign a string value foo to a parameter string_param for some_node and a string value bar to that same parameter string_param but for another_node upon running some_ros_executable that contains both, one may execute: Wildcards can be used for node names and namespaces as described in Remapping Names. Special Rule for Changing the Default Namespace, Supporting: Exact Relative Name Replacement, Supporting: Remap Topic and Service Names Separately, A user wants the node to subscribe to the same data after some processing, A company sells a generic mobile robot base with a ROS 2 driver. The replacement side of a rule must have a FQN which will become the new default namespace. Remove the need for double dash tokens (--), conventionally used to signify the end of CLI options for a command, by adding the --ros- prefix to all ROS specific command line flags e.g. I think you need to specify the node name under which this topic is published. As an example, to remap from foo to bar for some_ros_executable, one may execute: As is, this remapping rule applies to each and every node that some_ros_executable spawns unless explicitly ignored in code. However, parenthesis are not used; the wild cards always capture. This namespace gets prepended to all relative names used by the node. the following does not change it: Please start posting anonymously - your entry will be published after you log in or create a new account. ROS 2 Foxy Fitzroy installed on Ubuntu Linux 20.04 or newer. from launch. As an example, to assign a string value test to a parameter string_param for some_ros_executable, one may execute: As is, this parameter assignment applies to each and every node that some_ros_executable spawns unless explicitly ignored in code. The second part is the replacement for a matched name. A popular ROS 1 package actionlib creates 5 topics with the same namespace. roslaunch remap ROS Topic remap publish topic remap subscribe from publish topic remap publish topic remap rostopic and rosservice, may also be used to further scope remapping rules. Is there a way to remap a parameter by command line using the $ ros2 launch command? ROS 2 Remapping Use cases These use cases are being considered for remapping in ROS 2: Remap One Node in a Process Change a Namespace It attempts to be the same as ROS 1 syntax when possible. This use case is the ability to change the namespace of multiple names with one rule. The first case requires a wildcard to match the rest of a namespace. As an example, to disable logging to rosout and stdout but not to an external logging library for some_ros_executable, one may execute: Logging is fully enabled by default, thus --enable-* options are usually redundant unless a --disable-* option found earlier in the command line is being overridden. Instead of starting each process manually, they allow you to start multiple nodes with one command and add logic to your startup sequence. When launching the two turtlesim nodes, the only difference between them is their namespace values. As always, dont forget to source ROS 2 in every new terminal you open. You'll see the entire process to create, write, install, and start the launch file. ROS 1 has this feature using either the environment variable ROS_NAMESPACE or the argument __ns. The second part is the replacement for a matched name. ros2 launch <path_to_launch_file> Setting arguments To set the arguments that are passed to the launch file, you should use key:=value syntax. The included launch file names the node as turtlebot_teleop_keyboard. ROS2 launch files are a powerful tool for robotics applications. This option takes a YAML file with the following structure: Multiple nodes in a single executable can be targeted this way. will set the parameter string_param on any node in the namespace /foo. For example, you can set the value of background_r in the following way: ros2 launch <package_name> <launch_file_name> background_r:=255 or ros2 launch <path_to_launch_file> background_r:=255 Minimum logging level can be externally set either globally or per logger using the --log-level option. Now they are implemented in Python. Then if the replacment name does not begin with / it is automatically prefixed with the nodes default namespace to make it a FQN. Copy and paste the complete code into the launch/turtlesim_mimic_launch.py file: Copy and paste the complete code into the launch/turtlesim_mimic_launch.xml file: Copy and paste the complete code into the launch/turtlesim_mimic_launch.yaml file: All of the launch files above are launching a system of three nodes, all from the turtlesim package. In ROS 2 just one rule could remap them all. As an example, to assign an enclave path /foo/bar one may execute: As is, this enclave assignment applies to each and every Domain Participant that some_ros_executable spawns unless explicitly ignored in code or overridden via security environment variables. an empty set is a valid invocation. Other, alternative designs were under discussion. Remapping a node name is not possible using roslaunch. will set the parameter string_param on all nodes. I am using hydro on Ubuntu 12.04. The following launch file does not rename the node. Exact FQN replacement requires no wildcards. The name is remapped to the right side only if it exactly matches the left side of a rule. To avoid confusion they are required to be separated from tokens, substitutions, and each other by a /. Important note: the line order in launch files for remapping is very important. I know this is an old topic but I had a similar question today. Rely on full name addressing to disambiguate operator significance e.g. If both a node name prefix and URL scheme are given, the node name prefix must come first. You can create launch files using Python, XML, or YAML, and run them using the ros2 launch command. Remapping a node in a process requires a way to uniquely identify a node. If no URL scheme is given then the rule applies to both topics and services. Stop using the same := operator for parameter assignments and name remapping rules and introduce additional operators e.g. The syntax has been chosen to not conflict with special shell characters in bash. Partial matches are not allowed (e.g. The extra wildcards ? I commented the remapping so file looks like: I includeed this launch file and tried your answer and it does not rename the node. Goal: Create a launch file to run a complex ROS 2 system. roslaunch takes in one or more XML configuration files (with the .launch extension) that specify the parameters to set and nodes to launch, as well as the machines that they . In ROS 1 remapping works by passing in arguments to each node. Because a process can contain multiple nodes, there must be a way to uniquely identify a node in a process. How to change/remap ros node name in launch file? In ROS 1 the argument __ns:= could change the default namespace. and [] dont appear to enable more uses cases above. It still does not work. Exact relative replacement also requires no wildcards. [closed], Undefined reference to cv::Feature2D::compute. If the node name is not prefixed, the rule will be applied to all nodes in the process. The configuration of the system includes what programs to run, where to run them, what arguments to pass them, and ROS-specific conventions which make it easy to reuse components throughout the system by giving them each a different configuration. ROS 2 Remapping Use cases These use cases are being considered for remapping in ROS 2: Remap One Node in a Process Change a Namespace According to the docs ( http://wiki.ros.org/roslaunch/XML/remap ) remap affects all subsequent nodes. Both sides of a rule are expanded to FQN. There is no workaround. This allows a user to remap a relative name to another name. Fnmatch syntax may or may not match text with slashes depending on the option FNM_PATHNAME. Creative Commons Attribution Share Alike 3.0. articles/160_ros_command_line_arguments.md. There are two cases: changing part of a namespace, and changing the entire namespace. I want to rename the node launched in the included launch file. ROS 1 has this feature using the argument __name. The launch system in ROS 2 is responsible for helping the user describe the configuration of their system and then execute it as described. Finally the name is compared against the match part of the rule. The strings __name or __node can be given on the match part of a rule to signal a change of the nodes name. At the time of writing, most ROS specific arguments target and are thus parsed by rcl. Without remapping every instance of a node would require changes in code. A syntax like fnmatch is being considered. This is the ability to change a token in multiple names regardless of where it appears. Remapping is a feature that also exists in ROS 1. All relative names are expanded to the new namespace before any remapping rules are applied to them. This way the new rule matches against the name the user sees with introspection tools rather than the original name used in code. Nodes that are launched before any remap lines are not affected. The replacement must be a single token which will become the nodes new name. The replacement side must have a single token. Tasks 1 Setup Create a new directory to store your launch files: mkdir launch 2 Write the launch file Let's put together a ROS 2 launch file using the turtlesim package and its executables. I am using ROS 2 Galactic, which is the latest version of ROS 2 as of the date of this post. For example, /bar/*:=\1/bar matches the name /bar/foo use by a node with default namespace /ns with * capturing foo and replacement name /ns/foo/bar. ** matches zero or more tokens delimeted by slashes. Next, the launch description itself begins: The first two actions in the launch description launch the two turtlesim windows: The final action launches the mimic node with the remaps: The first two actions launch the two turtlesim windows: To run the launch file created above, enter into the directory you created earlier and run the following command: It is possible to launch a launch file directly (as we do above), or provided by a package. This is the ability to replace a name by exactly matching it. Specifying a URL scheme on the match side of the rule makes it exclusive to one type of name. The argument __node:= has the same effect. mimics /input/pose topic is remapped to /turtlesim1/turtle1/pose and its /output/cmd_vel topic to /turtlesim2/turtle1/cmd_vel. The replacement part of a rule may not have a URL scheme. A user may want to change a name used in one node without affecting the rest. The act of replacing one name with another is remapping. The syntax doesnt have a way to specify that a rule should be applied Prior to FQN expansion. It also increases command line verbosity. If the match part of a rule does not begin with /, *, or ** it is prefixed with /namespace/ to make it a FQN. This is the ability to change the basename of multiple names with one rule. The structure of a remapping rule is match:=replacement. What if they don't? Log messages use the new name immediately. This signficantly increases command line verbosity, but still avoids the need for flags. If you have control over the launch file you can use an argument to allow passing in a different name for the node name. See rcutils and rcl logging documentation for reference on existing logging levels. Remapping a node name is not possible using roslaunch. That would be really cumbersome to do so. To limit it to some_node, one may execute: Multiple parameter assignments can be performed at once using the --params-file option. Afterwards the reference operators are replaced with the matched content. Names are hard coded in ROS nodes, but they can be changed at runtime through remapping. If yes then how is it done. ros2 launch <path_to_launch_file> Setting arguments To set the arguments that are passed to the launch file, you should use key:=value syntax. Then the name is expanded to a FQN. Remapping names allows reusing the same node executable in different parts of the system. In ROS 2, this interface had to become more complex to cope with a larger set of configuration options, an ambiguity in remapping rules and parameter assignment syntax (as a result of the leading underscore name convention for hidden resources), a one-to-many relationship between executables and nodes, to name a few. As an example, to set a global logging level to DEBUG for some_ros_executable, one may execute: Loggers can be set using the --log-level option as well: The minimum logging level of a specific logger will override the globally specified minimum logger level. Before a name is remapped it is also expanded to FQN. When it is provided by a package, the syntax is: You learned about creating packages in Creating a package. To limit it to some_node, one may execute: Parameter assignment may be achieved using the --param/-p option. A robot that has multiple sensors of the same type could launch multiple instances of the same node with outputs remapped to different topics. On the match side __ns must be used by itself or with a nodename: prefix. I would like to rename a node from a launch file which includes other launch file. The act of replacing one name with another is remapping. So I found you can rename the node with remap, like this: For the record, just remapping the node name does not work, i.e. "Could not find parameter robot_description_semantic" URDF ROS . For single parameter assignment, use either. roslaunch is a tool for easily launching multiple ROS nodes locally and remotely via SSH, as well as setting parameters on the Parameter Server.It includes options to automatically respawn processes that have already died. The driver uses lots of names with the companys name in it: Another company incorporates the base into their product, and their customers want a ROS 2 interface, The second company doesnt want their interface to contain, Both sides of the remap rule are expanded to, First rule remaps token used in namespace, Second rule remaps token used as basename. To prevent ROS specific command line flags from colliding with user-defined ones, the former are scoped using the --ros-args flag and a trailing double dash token (--): Note that --ros-args -- i.e. For example in bash, the character * only has special behavior if it is surrounded by whitespace, but remap rules dont contain whitespace. Launch files written in Python, XML, or YAML can start and stop different nodes as well as trigger and act on various events. Both turtles in this system receive commands over the same topic and publish their pose over the same topic. The complete definition of a name is here. This syntax is identical to ROS 1. This option takes a single from:=to remapping rule. From a launch file Here's a minimal ROS2 launch file which just launches one node with params from a YAML file. The URL schemes rosservice:// and rostopic:// may only be given to topic or service name rules. The substitution operators (~ and {}) are replaced first. More than one set of ROS specific flags may appear in the same command line: This way, multiple sources, potentially unaware of each other, can append flags to the command line with no regard for previous sets. The second part is the replacement for a matched name. It looks the launch file you are using might already perform some kind of remapping internally: https://github.com/turtlebot/turtlebo Update 2: this only describes how to remap a topic. This is the case for name remapping rules or parameter assignments flags, to name a few. Because processes in ROS 2 can contain multiple nodes, it is possible multiple nodes in a process may use the same name for different purposes. The second requires a wildcard to match the basename at the end. In ROS 1 the argument __name:= could change the nodes name. Remapping rules have two parts. This description lays out the main roles of roslaunch from ROS 1 as: launch nodes launching nodes remotely via SSH setting parameters on the parameter server automatic respawning of processes that die static, XML based description of the nodes to launch, parameters to set, and where to run them These special operators are unique to the replacement part of a rule: The syntax for \1 through \9 was taken from backreferences in POSIX BRE. When this creates a name with // one slash is automatically deleted. Unique namespaces allow the system to start two nodes without node name or topic name conflicts. The first part is used to determine if the rule applies to a name. How To Display Launch Arguments for a Launch File in ROS2; Getting Started With OpenCV in ROS 2 Galactic (Python) Connect Your Built-in Webcam to Ubuntu 20.04 on a VirtualBox . The goal of the system is to launch two turtlesim windows, and have one turtle mimic the movements of the other. The syntax cant change all uses of a token with one rule. For example, you can set the value of background_r in the following way: ros2 launch <package_name> <launch_file_name> background_r:=255 or ros2 launch <path_to_launch_file> background_r:=255 ROS2 allows you to run individual nodes with the command: $ ros2 run <package_name> <node_name> This is nice and fun if you are just running a couple of nodes at the same time, but imagine you need to run 10-20 nodes like this. In ROS 1 remapping an actionlib client or server means creating 5 remapping rules. := behaves the same as it does in ROS 1. It works by first expanding the relative name and then doing FQN replacement. Client libraries also have APIs in code to pass remapping rules when the node is initialized. Supporting this use case with a single rule is not a priority. First we'll start with a simple launch file to start 2 nodes. This tutorial will explain everything you need to know about ROS2 launch files. See Using Python, XML, and YAML for ROS 2 Launch Files for a description of the different formats. I explain it better: my launch file loads the parameters for my node from some YAML files, but sometimes I want to test other parameters without modifying the YAML file using some kind of CLI overload. If a name begins with / it is called a Fully Qualified Name (FQN) otherwise it is called a relative name. The act of replacing one name with another is remapping. If the name matches it is remapped. --ros-remap, --ros-param, etc. *, and ** match whole tokens only. foo*). rosparam://this:=that would result in a that string value being assigned to parameter this while rosremap://this:=that would result in name this being remapped to name that. roslaunch my_robot_tutorials remap_test.launch - you'll have the same result as with the rosrun argument. 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