{
  "id": "ros2-tf2-listener",
  "name": "ROS 2 tf2 transform listener and turtle-following node",
  "summary": "Official ROS geometry tutorial node that spawns turtle2, looks up its transform relative to a target frame and publishes Twist velocity commands to follow that target. It is an installed ROS 2 console entrypoint with ROS graph effects, not a direct Python-file main or a verified robot controller.",
  "framework": "ros2-tf2",
  "kind": "community_skill",
  "capabilities": [
    "coordinate-transforms",
    "frame-following",
    "velocity-command",
    "robotics-middleware"
  ],
  "aliases": [
    "ROS 2",
    "tf2",
    "TransformListener",
    "Buffer",
    "lookup_transform",
    "turtlesim",
    "Twist"
  ],
  "robots": [
    "turtlesim"
  ],
  "source": {
    "repository": "https://github.com/ros/geometry_tutorials",
    "commit": "8e677416092ac97606a4a23256c815ba2fe762d4",
    "path": "turtle_tf2_py/turtle_tf2_py/turtle_tf2_listener.py",
    "url": "https://github.com/ros/geometry_tutorials/blob/8e677416092ac97606a4a23256c815ba2fe762d4/turtle_tf2_py/turtle_tf2_py/turtle_tf2_listener.py",
    "sha256": "bb2c9f91a430216878a831f355f529761dadb8603e3e390ecf6ec9626fa4713f",
    "bytes": 4419,
    "authors": [
      "Open Source Robotics Foundation, Inc."
    ]
  },
  "license": {
    "spdx": "Apache-2.0",
    "url": "https://github.com/ros/geometry_tutorials/blob/8e677416092ac97606a4a23256c815ba2fe762d4/LICENSE",
    "scope": "Selected listener source under its explicit Apache-2.0 header, copyright 2021 Open Source Robotics Foundation, Inc. Preserve attribution, license and applicable notices. The package also declares BSD for other material; this source review does not clear the full package, dependencies or physical-robot use.",
    "verified": true
  },
  "artifact": {
    "kind": "code",
    "format": "python"
  },
  "requirements": {
    "python": null,
    "packages": [
      "Compatible ROS 2 rclpy environment with the context-manager init API used by this source",
      "tf2_ros",
      "geometry_msgs",
      "turtlesim_msgs",
      "Installed turtle_tf2_py package exposing the reviewed console entrypoint"
    ],
    "hardware": [],
    "system": [
      "Configured ROS graph providing the relative spawn service and appropriate turtle1/turtle2 transforms",
      "Reviewed namespace, target_frame parameter and intended turtle2/cmd_vel subscribers"
    ],
    "notes": "The package is labeled version 0.7.0 at a Rolling-branch source pin; neither label establishes a tested ROS distribution, Python version or operating system. The node defaults target_frame to turtle1, requests turtle2 at x=4.0, y=2.0, theta=0.0 and, after spawning, queries a transform into turtle2 with rclpy.time.Time(). On a nominal one-second timer it publishes angular z from atan2 and linear x as 0.5 times translation distance. The period and gains are source settings, not measurements. Transform failures are logged and return without an explicit zero-velocity stop. No obstacle check or speed clamp is present. This node does not generate its required transforms, and a single source file is insufficient. ROS graph dependencies, shutdown behavior, hardware remappings and compatibility remain untested."
  },
  "invocation": {
    "entrypoint": "ros2 run turtle_tf2_py turtle_tf2_listener",
    "notes": "Installed ROS 2 console command backed by the pinned setup.py registration turtle_tf2_py.turtle_tf2_listener:main. The source defines main without a __main__ guard; direct python-file execution is not the declared node invocation. Starting the console entrypoint initializes rclpy, calls a spawn service and can publish velocity commands to the configured graph. No physical-controller compatibility or safe stopping is established. The Hub supplies inert source metadata with no preparation/execution adapter and ran no ROS node or simulator."
  },
  "compatibility": [
    {
      "runtime": "unknown",
      "runtime_version": "unknown",
      "robot": "unknown",
      "controller": "unknown",
      "observation": "unknown",
      "os": "unknown",
      "status": "unknown"
    }
  ],
  "access": {
    "mode": "source_reference",
    "hub_prepare": false,
    "instructions": "Read the pinned node, package declarations and setup registration before configuring the intended ROS graph. This source reference does not install or execute code.",
    "setup_url": "https://github.com/ros/geometry_tutorials/blob/8e677416092ac97606a4a23256c815ba2fe762d4/turtle_tf2_py/setup.py"
  },
  "evidence": {
    "level": "source_reviewed",
    "runtime_verification": "not_run",
    "checked_at": "2026-10-18",
    "inspection": "Complete node read as inert text and Python AST parsed without import or execution. Source, license, package XML and setup bytes matched SHA-256, lengths and immutable-tree Git blob pins. Installed console registration and ROS graph effects were inspected; no ROS/Python/OS combination, controller, simulator or task result was tested."
  },
  "maintenance": {
    "record_version": "reviewed-20261018-bb2c9f91a430",
    "last_checked": "2026-10-18",
    "upstream_status": "source_pinned"
  }
}