CDAP Common: CLI

Introduction

The CLI module contains a Command-Line Interface (CLI) framework for building your own CLI complete with auto-completion and command-parsing.

Usage

To use this CLI framework, you must first define a command:

public class EchoCommand implements Command {

  @Override
  public void execute(Arguments arguments, PrintStream output) throws Exception {
    output.println(arguments.get("some-input"));
  }

  @Override
  public String getPattern() {
    return "echo <some-input>";
  }

  @Override
  public String getDescription() {
    return "Echoes whatever is passed";
  }

}

This will define a command that would match the user input echo something, for example. In execute(), arguments.get("some-input") would then return something, because something was matched to <some-input> from the getPattern() implementation. You can then instantiate a CLI instance and have it use your command:

public static void main(String[] args) throws IOException {
  CLI cli = new CLI<Command>(new EchoCommand());
  cli.run(args, System.out);
}

If args is empty, then the CLI will start in interactive mode. This will provide a shell (similar to bash) from which the user can enter in multiple commands and use auto-completion.

If args is not empty, then the CLI will assume the args are the parts of a command, and execute the command. In this example, if args is ["echo", "hello"], then the CLI will match the input to the EchoCommand command and pass "hello" as the argument value for the "some-input" argument.

Examples

• HelloCLI: the simple example presented above
• NoteCLI: notetaking CLI that demonstrates usage of multiple commands and completers