getopt usage help to stderr?

[Salih Dincer]

On Tuesday, 8 April 2025 at 20:14:56 UTC, Andy Valencia wrote:
>
> p.s. Ironically, I could probably have coded a getopt in less 
> time than I've spent on std.getopt...

:)

Please try the following example with the parameters -h, -e, -l, 
and -v in that order:

```d
import std.array : appender;
import std.getopt, std.stdio;

void main(string[] args)
{
     enum errMsg = "\nPlease try again!";
     string test;
     bool verbose;

     try
     {
         auto rslt = getopt(
             args,
             "exit|e", "Exit process", &test,
             "verbose|v", "Enable verbose output", &verbose
         );

         if (rslt.helpWanted)
         {
             // Capture help text to a string
             import std.array : appender;
             import std.format : formattedWrite;

             auto helpText = appender!string();
             defaultGetoptFormatter(helpText, args[0], 
rslt.options);

             // Output to stderr
             stderr.write(helpText.data);
             return;
         }
     }
     catch (Exception e)
     {
         stderr.writeln(e.msg, errMsg); // ... Please try again!
         // Also output help on error
         auto helpText = appender!string();
         defaultGetoptFormatter(helpText, args[0], 
getopt(args).options);
         stderr.write(helpText.data);
         return;
     }

     // Your program logic here
     if (verbose)
       writeln("Verbose Mode: on");
}

```

SDB at 79