Your first cli-fp program

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Start with one root command when your program has one default action. The complete program below is also the repository's QuickStartDemo, which is compiled by the Windows and Linux example smoke checks.

The program follows the normal v1.4.x ownership model: THelloCommand descends from TBaseCommand, Main is its instance and owns --name, and App is the ICLIApplication that parses the invocation and calls Main.Execute.

program QuickStartDemo;

{$mode objfpc}{$H+}{$J-}

uses
  CLI.Interfaces, CLI.Application, CLI.Command;

type
  THelloCommand = class(TBaseCommand)
  public
    function Execute: Integer; override;
  end;

function THelloCommand.Execute: Integer;
var
  PersonName: string;
begin
  if not GetParameterValue('--name', PersonName) then
    PersonName := 'World';
  WriteLn('Hello, ', PersonName, '!');
  Result := 0;
end;

var
  App: ICLIApplication;
  Main: THelloCommand;
begin
  Main := THelloCommand.Create('', 'Print a greeting');
  Main.AddStringParameter('-n', '--name', 'Name to greet', False, 'World');
  App := CreateCLIApplication('hello', '1.0.0', Main);
  Halt(App.Execute);
end.

Compile from a clone of this repository:

fpc -Fu./src ./examples/QuickStartDemo/QuickStartDemo.lpr
./examples/QuickStartDemo/QuickStartDemo --name Ada

fpc "-Fu.\src" .\examples\QuickStartDemo\QuickStartDemo.lpr
.\examples\QuickStartDemo\QuickStartDemo.exe --name Ada

Both commands print Hello, Ada!. Run --help to see generated usage and the option description.

What the program does

• TBaseCommand supplies parameter registration and lookup.
• An empty command name creates the root (default) action, so users run hello --name Ada, not hello greet --name Ada.
• CreateCLIApplication parses arguments, validates registered options, shows help, and returns the exit code from Execute.

Next, choose whether your application should remain a root command or grow into named or nested commands. For common variations, go to How do I...?.