Command Line Tooling

JasperFx includes a lightweight CLI framework for building commands that integrate with Microsoft.Extensions.Hosting.

Enabling the CLI

Wire up the JasperFx command line by calling ApplyJasperFxExtensions on your host builder:

await Host
    .CreateDefaultBuilder()
    .ApplyJasperFxExtensions()
    .RunJasperFxCommands(args);

^{snippet source | anchor}

await Host
    .CreateDefaultBuilder()
    .ApplyJasperFxExtensions()
    .RunJasperFxCommands(args);

^{snippet source | anchor}

Alternatively, use RunJasperFxCommands for more control over host configuration:

var builder = Host.CreateDefaultBuilder();

builder.ConfigureServices(services =>
{
    // Register your services here
});

await builder
    .ApplyJasperFxExtensions()
    .RunJasperFxCommands(args);

^{snippet source | anchor}

var builder = Host.CreateDefaultBuilder();

builder.ConfigureServices(services =>
{
    // Register your services here
});

await builder
    .ApplyJasperFxExtensions()
    .RunJasperFxCommands(args);

^{snippet source | anchor}

Built-in Commands

JasperFx ships with several commands out of the box:

Command	Description
help	List all available commands
describe	Describe the application configuration
check-env	Run all registered environment checks

Command Discovery

Commands are discovered automatically from referenced assemblies that carry the [JasperFxTool] attribute. Your own commands are found through assembly scanning.

Machine-readable command catalog

help --json writes the command catalog to stdout as JSON — each verb's name and description — for tooling that needs to introspect an app's commands:

dotnet run -- help --json

[
  { "name": "check-env", "description": "Execute all environment checks against the application" },
  { "name": "describe", "description": "Writes out a description of your running application ..." }
]

Like help itself, this runs without starting the host (no database/broker connections), so it is cheap to call. The Aspire dashboard integration uses it to discover a service's verbs.

Topics

• Writing Commands -- Create synchronous and async commands
• Arguments and Flags -- Define inputs with attributes
• Environment Checks -- Validate runtime dependencies
• Describe -- Customize the describe output