built-in "-help" usage info

[doggy8088]

Do you have built-in usage info when program use -help or --help?

[mikeruhl]

Yes, either will work. Given this example:

static void Main(string[] args)
{
    var f = Flag.String("path", string.Empty, "path to file");
    var m = Flag.String("message", "hello world", "message to place in file");
    Flag.Parse();
    Console.WriteLine($"Path supplied: {f}");
    Console.WriteLine($"message: {m}");
}

if I run .\TestApp.exe -help
I will get:

Usage of C:\Users\miker\source\temp\TestApp\TestApp\bin\Debug\netcoreapp3.1\TestApp.dll:
  -message string
        message to place in file (default "hello world")
  -path string
        path to file

It's important to note that this default behavior ignores that you didn't include arguments. If you were to have different error handling like this example:

static void Main(string[] args)
{
    var flagSet = new FlagSet("main", ErrorHandling.PanicOnError);
    var f = flagSet.String("path", string.Empty, "path to file");
    var m = flagSet.String("message", "hello world", "message to place in file");
    flagSet.Parse(args);
    Console.WriteLine($"Path supplied: {f}");
    Console.WriteLine($"message: {m}");
}

It will still print the help message but also throw an exception, which will result in a non-zero exit code .\TestApp.exe -help:

Usage of main:
  -message string
        message to place in file (default "hello world")
  -path string
        path to file
Unhandled exception. System.InvalidOperationException: flag: help requested
   at GoFlag.FlagSet.Parse(String[] arguments)
   at TestApp.Program.Main(String[] args) in C:\Users\miker\source\temp\TestApp\TestApp\Program.cs:line 15

Any other questions? Thanks, I will add this to the documentation.

[doggy8088]

I think you can wrap a try/catch in the Flag.Parse(); for displaying usage information purpose. You can simply just put sample code in your docs.

[mikeruhl]

Added some additional documentation around error handling here: 7ca5f38