Restricting D applications to a single instance

[Preetpal]

On Monday, 22 February 2021 at 02:39:58 UTC, Steven Schveighoffer 
wrote:
> On 2/21/21 9:29 PM, Preetpal wrote:
>> I want to restrict a D application to a single instance. Is 
>> there a way to do this using the D standard library?
>
> When you say "application", you mean a class or type?

I actually meant that you cannot have two instances of an 
application (executable) running at once.

So for example, if the functionality were implemented for a text 
editor, you would only be able to open one process (or instance) 
of that text editor. Like if you were to double click an 
executable on Windows in file explorer repeatedly, it would only 
open once, not multiple times.