Hello.

Help me please to understand, how to show usage help to user, who enter wrong options?
For example, user not provided required filename.
I want to show error message, and program usage help text.
But likely getopt don't provide help text until valid options will be parsed.

Reduced code:
///////////////
import std.stdio: writefln;
import std.getopt;

void main (string[] args)
{
  string fname;
  GetoptResult helpInfo;

  try
  {
    helpInfo = getopt(
      args,
      std.getopt.config.required, "file|f", "File name", &fname);

    writefln("Options parsed: fname=%s", fname);
  }
  catch(Exception e)
  {
    writefln("\nERROR: %s", e.msg);
    defaultGetoptPrinter("Program usage:", helpInfo.options);
  }
}
///////////////

Output:
ERROR: Required option file|fwas not supplied
Program usage:

What you're trying to do is currently impossible. I filed a bug (https://issues.dlang.org/show_bug.cgi?id=14525) because what you're trying to do really should be possible.

import std.stdio : writefln;
import std.getopt;

void main(string[] args)
{
    string fname;
    try
    {
        getopt(args, std.getopt.config.required, "file|f", "File name", &fname);
        writefln("Options parsed: fname=%s", fname);
    }
    catch (GetOptException e)
    {
        writefln("\nERROR: %s", e.msg);
        auto p = ["placeholder"];
        auto r = getopt(p, "file|f", "File name", &fname);
        defaultGetoptPrinter("Program usage:", r.options);
    }
}

Thank you, Brian!

On Wednesday, 29 April 2015 at 22:02:29 UTC, novice2 wrote:
> Hello.
>
> Help me please to understand, how to show usage help to user, who enter wrong options?
> For example, user not provided required filename.
> I want to show error message, and program usage help text.
> But likely getopt don't provide help text until valid options will be parsed.
>
> Reduced code:
> ///////////////
> import std.stdio: writefln;
> import std.getopt;
>
> void main (string[] args)
> {
>   string fname;
>   GetoptResult helpInfo;
>
>   try
>   {
>     helpInfo = getopt(
>       args,
>       std.getopt.config.required, "file|f", "File name", &fname);
>
>     writefln("Options parsed: fname=%s", fname);
>   }
>   catch(Exception e)
>   {
>     writefln("\nERROR: %s", e.msg);
>     defaultGetoptPrinter("Program usage:", helpInfo.options);
>   }
> }
> ///////////////
>
> Output:
> ERROR: Required option file|fwas not supplied
> Program usage:

Also, I suggest you look at docopt:
http://code.dlang.org/packages/docopt

It makes the whole parsing of CLI arguments very nice and easy.