Running only one instance of the app

[Bagomot]

Hello everyone! I need to allow only one instance of my 
application to run.

I use this way for Windows:
```d
import std.stdio;
import std.utf;

version(Windows) {
	import core.sys.windows.winbase;
	import core.sys.windows.windows;
}

void main(string[] args) {
	string mutexName = "xxxx";

	version(Windows) {
		HANDLE mutex; //global handle mutex
		try {
			mutex=CreateMutex(NULL, true, uuidMutexName.toUTF16z);
			DWORD result;
			result = WaitForSingleObject(mutex, 0);
			if(result != WAIT_OBJECT_0) {
				writeln("The app is already running!");
   				return;
   			}
		} catch(Exception e) {
			writeln(e.msg);
		}

		scope(exit) {
			ReleaseMutex(mutex);
			CloseHandle(mutex);
		}
	}

	//todo

	while(true){}
}
```
This is where the application creates a global mutex with a 
specific name. At startup, the application checks for the 
presence of such a mutex. If it is, then a instance of the 
application has already been launched.

This works for Windows. I need something similar for Linux and 
Macos.

Tell me how, if you know. Maybe the standard library D already 
has the required functionality? Or are there better ways to only 
run one instance of the app?