Command

protocol Command : AnyCommand

Overview

Both Command and CommandGroup conform to AnyCommand which provides the basic requirements all command-like types need. In addition to those types, a Command requires zero or more CommandArguments.

Below is a sample command that generates ASCII picture of a cow with a message.

struct CowsayCommand: Command {
    public struct Signature: CommandSignature {
        @Argument(name: "message")
        var message: String

        @Option(name: "eyes", short: "e")
        var eyes: String?

        @Option(name: "tongue", short: "t")
        var tongue: String?

        public init() { }
    }

    var help: String {
        "Generates ASCII picture of a cow with a message."
    }

    public init() { }
    public func run(using context: CommandContext, signature: Signature) throws {
        let eyes = signature.eyes ?? "oo"
        let tongue = signature.tongue ?? " "
        let padding = String(repeating: "-", count: message.count)
        let text: String = """
          \(padding)
        < \(message) >
          \(padding)
                  \\   ^__^
                   \\  (\(eyes)\\_______
                      (__)\\       )\\/\\
                        \(tongue)  ||----w |
                           ||     ||
        """
        context.console.print(text)
    }
}

Meanwhile you can use the Command in an executable target like:

let console: Console = Terminal()
var input = CommandInput(arguments: CommandLine.arguments)
var context = CommandContext(console: console, input: input)

try console.run(CoswayCommand(), with: context)

Use Commands to register commands and create a CommandGroup.

Here is a simple example of the command in action, assuming it has been registered as "cowsay".

swift run cowsay Hello
  -----
< Hello >
  -----
          \   ^__^
           \  (oo\_______
              (__)\       )\/\
                   ||----w |
                   ||     ||

And an example with flags:

swift run cowsay "I'm a dead cow" -e xx -t U
  --------------
< I'm a dead cow >
  --------------
          \   ^__^
           \  (xx\_______
              (__)\       )\/\
                U  ||----w |
                   ||     ||