Create the Project

Let's start by creating a new console application and adding the Spectre.Console.Cli package:

dotnet new console -n GreetingApp
cd GreetingApp
dotnet add package Spectre.Console.Cli

The output confirms the package was installed. Now we're ready to write some code.

Create Your First Command

Open Program.cs and replace its contents with our greeting command:

internal class GreetCommand : Command<GreetCommand.Settings>
{
    public class Settings : CommandSettings
    {
        [CommandArgument(0, "<name>")]
        [Description("The name to greet")]
        public string Name { get; init; } = string.Empty;
    }
  
    protected override int Execute(CommandContext context, Settings settings, CancellationToken cancellation)
    {
        System.Console.WriteLine($"Hello, {settings.Name}!");
        return 0;
    }
}

Run the application:

You should see Hello, Alice! printed to the console. Notice the <name> in angle brackets? That means it's required. Try running without a name to see the built-in error handling:

The CLI automatically tells you that the name argument is missing. No extra code needed.

Add an Option

Arguments are great for required values, but sometimes you want optional behavior. Let's add a --count option to repeat the greeting:

internal class GreetCommand : Command<GreetCommand.Settings>
{
    public class Settings : CommandSettings
    {
        [CommandArgument(0, "<name>")]
        [Description("The name to greet")]
        public string Name { get; init; } = string.Empty;
  
        [CommandOption("-c|--count")]
        [Description("Number of times to greet")]
        [DefaultValue(1)]
        public int Count { get; init; } = 1;
    }
  
    protected override int Execute(CommandContext context, Settings settings, CancellationToken cancellation)
    {
        for (var i = 0; i < settings.Count; i++)
        {
            System.Console.WriteLine($"Hello, {settings.Name}!");
        }
        return 0;
    }
}

Run the application with the new option:

dotnet run -- Alice --count 3

The greeting appears three times. The -c short form works too:

Options default to the value you specify (here, 1), so the original command still works:

Explore Built-in Help

Every Spectre.Console.Cli application gets automatic help. Run with --help:

The output shows your command's usage, the required <name> argument, and the optional --count flag with its description. All of this was generated from the attributes we added. The [Description] attributes appear right in the help text.

You didn't write any help-rendering code. It just works.

See Validation in Action

Spectre.Console.Cli validates input automatically. Try passing an invalid count:

dotnet run -- Alice --count abc

The CLI shows an error explaining that abc isn't a valid integer. Try omitting the required name:

Again, a clear error message appears. This built-in validation saves you from writing repetitive error-handling code.