ROS Package bob_launch

bob_launch is a powerful meta-launcher for ROS 2 that enables dynamic system orchestration using YAML or JSON configuration files. It allows you to define, compose, and launch complex ROS 2 graphs without writing boilerplate Python launch files.

High-Level Capabilities

• Dynamic Orchestration: Spawn nodes or include other launch files based on external configuration.
• Composition over Coding: Define your entire ROS system in simple YAML.
• Streamlined Workflow: Use the launch.sh wrapper or native ROS 2 launch arguments.
• Auto-Abort Protection: Optionally shut down the entire launch tree if any critical node exits (ideal for Docker/CI).
• Global Parameters: Inject a shared parameter file into all nodes launched within a configuration.
• Path Placeholders: Use //PKGSHARE/ (current node package) or //PKGSHARE:pkg/ to dynamically resolve ROS 2 package share directories in parameters and arguments.
• Environment Substitution: Support for shell-like ${VAR} or ${VAR:-default} syntax in all configuration fields and relevant launch arguments.

Native ROS 2 Usage (Preferred)

You can call the launch file directly using standard ROS 2 launch arguments:

ros2 launch bob_launch generic.launch.py config:=my_config.yaml

To pass an optional global node parameter file:

ros2 launch bob_launch generic.launch.py config:=my_config.yaml config_nodes:=node_params.yaml

Note: You can also use the environment variable BOB_LAUNCH_CONFIG=./my_config.yaml as an alternative to the config:= argument.

Fast Execution: launch.sh

The launch.sh script is a convenient wrapper that simplifies execution by handling environment variables and temporary file management for you.

1. Launch from a file

ros2 run bob_launch launch.sh my_config.yaml

2. Launch with a global parameter file

ros2 run bob_launch launch.sh my_config.yaml global_params.yaml

3. Launch from a JSON config file

ros2 run bob_launch launch.sh my_config.json

Advanced Usage

bob_launch is designed to be highly scriptable, making it an ideal tool for AI Agents needing to spawn ROS components on the fly.

Pipe a String Directly (Dynamic Spawning)

An agent can generate a YAML string and pipe it directly to the launcher without creating a persistent file:

echo "- name: talker
  package: demo_nodes_cpp
  executable: talker" | ros2 run bob_launch launch.sh

Multi-File Composition

You can quickly composite different system “layers” (e.g., base drivers + perception + mission logic) by concatenating files into the pipe:

cat base_robot.yaml nav2_stack.yaml custom_logic.yaml | ros2 run bob_launch launch.sh

Dynamic Substitution & Placeholders

bob_launch supports powerful dynamic string substitution in all configuration fields and launcher arguments (like config:= and config_nodes:=).

Environment Variables (${VAR})

Supports shell-like syntax for dynamic values:

• ${MYVAR}: Replaces with the value or an empty string.
• ${MYVAR:-/default/path/}: Replaces with the value or the specified default if unset.

Path Placeholders (//PKGSHARE)

Avoid hardcoded absolute paths by dynamically resolving ROS 2 package share directories:

• //PKGSHARE/: Resolves to the share directory of the package defined for the current entity (implicit).
• //PKGSHARE:pkg_name/: Resolves to the share directory of pkg_name (explicit).

Combination & CLI Usage

These mechanisms can be combined and even used directly in the ros2 launch command arguments:

ros2 launch bob_launch generic.launch.py \
  config:='//PKGSHARE:my_pkg/config/${ROBOT_ENV:-dev}.yaml'

To disable environment substitution, set BOB_SUBSTITUTE_ENV_VARS=0.

Configuration Schema

Spawning Nodes

```yaml

• name: usb_cam # Optional: defaults to executable_name + random suffix package: usb_cam executable: usb_cam_node_exe arguments: # Optional: list of CLI arguments
  • –ros-args

File truncated at 100 lines see the full file

Changelog for package bob_launch

1.0.1 (2026-02-03)

• Fix linter and style issues for ROS2 compliance
• Standardize docstrings and copyright headers
• Refactor launch parameter
• Add support for 'prefix' parameter in configuration
• Add support for inline 'parameters' in node configuration
• Add support for '//PKGSHARE' and '//PKGSHARE:pkg' placeholders for dynamic path resolution
• Add support for environment variable substitution (${VAR} and ${VAR:-default}) in configuration files
• Enable dynamic placeholder resolution for 'config' and 'config_nodes' launch arguments
• Standardize placeholder resolution across all configuration fields including 'launch_ns'
• Add support for native ROS 2 remappings in node configurations
• Add support for [respawn_delay]{.title-ref} in node configurations
• Contributors: Bob Ros

1.0.0 (2026-02-02)

• Initial release
• Contributors: Bob Ros