launch_ext - Launch Extensions

Extended functionality for ROS 2 launch system providing additional actions, substitutions, and conditions.

Table of Contents

• Actions
  • ExecuteProcessExt
  • IncludePackageLaunchFile
  • LogRotate
  • MakeDeviceNode
  • SetLaunchConfigurationIfNotNone
  • WriteFile
  • Git Repository Actions
  • Middleware Configuration
• Conditions
• Substitutions

Actions

ExecuteProcessExt

Enhanced process execution action with additional features beyond the standard ExecuteProcess.

ExecuteProcessExt(
    cmd=['my_command', '--arg'],
    name='my_process',
    output='both'
)

Features:

• Extended process management capabilities
• Enhanced output handling
• Additional lifecycle management

IncludePackageLaunchFile

Include launch files from packages with enhanced functionality.

IncludePackageLaunchFile(
    package='my_package',
    launch_file='my_launch.py'
)

Parameters:

• package: Name of the package containing the launch file
• launch_file: Path to the launch file within the package

LogRotate

Manage log file rotation to prevent disk space issues.

LogRotate(
    log_file='/path/to/logfile.log',
    max_size='100MB',
    backup_count=5
)

Parameters:

• log_file: Path to the log file to rotate
• max_size: Maximum size before rotation
• backup_count: Number of backup files to keep

MakeDeviceNode

Create Linux device nodes for USB devices that are not automatically created by the kernel or when udev is not permitted.

MakeDeviceNode(
    "/dev/tty-magnetometer",
    "ttyUSB",
    "Prolific Technology Inc.",
    "USB-Serial Controller D"
)

Parameters:

• target_node: Path where the device node should be created
• device_type: Type of device (e.g., "ttyUSB")
• manufacturer: USB device manufacturer name
• product: USB device product name

Will create a device node at /dev/tty-magnetometer if it does not already exist. The device node will be created if the USB device with the vendor name Prolific Technology Inc. and product name USB-Serial Controller D is connected.

SetLaunchConfigurationIfNotNone

Conditionally set launch configurations only if the value is not None.

SetLaunchConfigurationIfNotNone(
    name='my_config',
    value=LaunchConfiguration('optional_param')
)

Parameters:

• name: Configuration parameter name
• value: Value to set (only if not None)

WriteFile

Write content to a file during launch execution.

WriteFile(
    file_path='/tmp/config.txt',
    content='configuration data'
)

Parameters:

• file_path: Path where the file should be written
• content: Content to write to the file

Git Repository Actions

LogRepoInfo

Log git repository information including branch, commit, and status.

LogRepoInfo("/path/to/repo")

Parameters:

• path: Path to the git repository

VerifyRepoCommit

Verify that a repository is at a specific commit hash.

VerifyRepoCommit(
    "/path/to/repo",
    "abc123...",
    pass_on_failure=False
)

Parameters:

• path: Path to the git repository
• commit: Expected commit hash
• pass_on_failure: Whether to continue on verification failure

VerifyRepoClean

Verify that a repository has no uncommitted changes.

VerifyRepoClean(
    "/path/to/repo",
    pass_on_failure=False
)

Parameters:

• path: Path to the git repository
• pass_on_failure: Whether to continue on verification failure

Middleware Configuration

ConfigureZenoh

Configure Zenoh middleware for ROS 2 communication.

ConfigureZenoh(
    with_router=True,
    router_config={'port': 7447},
    session_config={'mode': 'peer'}
)

Parameters:

• with_router: Whether to start a Zenoh router
• router_config: Router configuration overrides
• session_config: Session configuration overrides

ConfigureFastDDS

Configure FastDDS middleware settings.

ConfigureFastDDS(
    config_file='/path/to/fastdds.xml'
)

Conditions

EnumEqual

Check if a substitution value equals a specific enum value.

from enum import Enum

class Mode(Enum):
    DEBUG = "debug"
    RELEASE = "release"

EnumEqual(
    LaunchConfiguration('build_mode'),
    Mode.DEBUG
)

Parameters:

• substitute: Substitution to evaluate
• check_enum_value: Enum value to compare against

Substitutions

Templated

Template-based string substitution using Python's string.Template.

Templated("Hello ${name}, mode is ${mode}")

Uses launch configurations as template variables.

Unary

Unary operation substitution for mathematical expressions.

Unary('-', LaunchConfiguration('value'))

WriteTempFile

Create a temporary file with specified content and return its path.

WriteTempFile("temporary content")

Returns the path to the created temporary file.

YAMLToFile / YamlToJson

Convert YAML content to JSON format.

YamlToJson(
    FileContent(file_path),
    quote_output=True
)

Parameters:

• file_content_substitution: Source of YAML content
• quote_output: Whether to wrap JSON in quotes

ResolveHost

Resolve hostname to IP address.

ResolveHost("example.com")

Xacro

Process Xacro files for robot descriptions.

Xacro("robot.urdf.xacro")