• BoQsc (90/90) Aug 19 2023 I'm sharing some code here.
• BoQsc (91/91) Aug 20 2023 #### Update: GetUserName by print to stdout

BoQsc <vaidas.boqsc gmail.com> writes:

I'm sharing some code here.
**It's not completely tested and might contain serious mistakes, 
repetitions, bad style and readabilty.
But it seems to work.**

Critique, improvements and feedback might help.



This code retrieves username of the current windows user using 
Windows API (Win32).

![img1](https://i.imgur.com/aNyyglu.png)

**WindowsGetUserName.d**
```
import core.sys.windows.windows;
import std.conv;
import std.stdio;
import std.range;

pragma(lib, "advapi32.lib");

/**
  * Retrieves the currently logged-in user's name in a safe manner.
  *
  * This function first determines the required buffer size, 
allocates memory for the username,
  * and then retrieves the username.
  *
  * Returns:
  *   - The username as a string if successful.
  *   - An empty string if an error occurs.
  */
string getSafeUsername()  system {
     wchar[] userName;
     DWORD userNameSize = 0;

     // First, try GetUserNameW (Unicode version)
     if (!GetUserNameW(null, &userNameSize)) {
         int error = GetLastError();
         if (error != ERROR_INSUFFICIENT_BUFFER) {
             // Failed for a reason other than an insufficient 
buffer
             return "";
         }
     }

     // Allocate memory for userName
     scope(exit) userName.length = 0; // Ensure memory is released 
if an exception occurs
     userName.length = userNameSize;

     // Retrieve the user name by calling GetUserNameW
     if (GetUserNameW(userName.ptr, &userNameSize)) {
         // Successfully retrieved the user name, convert it to a 
string
         return to!string(userName);
     }

     // If GetUserNameW fails, try GetUserNameA (ANSI version)
     char[] userNameA;
     userNameSize = 0;

     if (!GetUserNameA(null, &userNameSize)) {
         int errorA = GetLastError();
         if (errorA != ERROR_INSUFFICIENT_BUFFER) {
             // Failed for a reason other than an insufficient 
buffer
             return "";
         }
     }

     // Allocate memory for userNameA
     scope(exit) userNameA.length = 0; // Ensure memory is 
released if an exception occurs
     userNameA.length = userNameSize;

     // Retrieve the user name by calling GetUserNameA
     if (GetUserNameA(userNameA.ptr, &userNameSize)) {
         // Successfully retrieved the user name using ANSI 
version, convert it to a string
         return to!string(userNameA);
     }

     // Both GetUserNameW and GetUserNameA failed, return an empty 
string
     return "";
}

/**
  * The entry point of the application.
  */
void main() {
     string username = getSafeUsername();
     if (!username.empty) {
         writeln("Logged-in user name: ", username);
     } else {
         writeln("Failed to retrieve the user name.");
     }
}

```


Footnotes
https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getusernamea
https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getusernamew
https://github.com/dlang/dmd/blob/master/druntime/src/core/sys/windows/winbase.d#L1903-L1904

BoQsc <vaidas.boqsc gmail.com> writes:

Main function has been updated with `string[] args` and a new 
feature:
```
     if (args.length > 1 && args[1] == "print") {
		write(username);
     }
```



`WindowsGetUserName.exe print`




![img1](https://i.imgur.com/dWPlo8L.png)


```d
import core.sys.windows.windows;
import std.conv;
import std.stdio;
import std.range;

pragma(lib, "advapi32.lib");

/**
  * Retrieves the currently logged-in user's name in a safe manner.
  *
  * This function first determines the required buffer size, 
allocates memory for the username,
  * and then retrieves the username.
  *
  * Returns:
  *   - The username as a string if successful.
  *   - An empty string if an error occurs.
  */
string getSafeUsername()  system {
     wchar[] userName;
     DWORD userNameSize = 0;

     // First, try GetUserNameW (Unicode version)
     if (!GetUserNameW(null, &userNameSize)) {
         int error = GetLastError();
         if (error != ERROR_INSUFFICIENT_BUFFER) {
             // Failed for a reason other than an insufficient 
buffer
             return "";
         }
     }

     // Allocate memory for userName
     scope(exit) userName.length = 0; // Ensure memory is released 
if an exception occurs
     userName.length = userNameSize;

     // Retrieve the user name by calling GetUserNameW
     if (GetUserNameW(userName.ptr, &userNameSize)) {
         // Successfully retrieved the user name, convert it to a 
string
         return to!string(userName);
     }

     // If GetUserNameW fails, try GetUserNameA (ANSI version)
     char[] userNameA;
     userNameSize = 0;

     if (!GetUserNameA(null, &userNameSize)) {
         int errorA = GetLastError();
         if (errorA != ERROR_INSUFFICIENT_BUFFER) {
             // Failed for a reason other than an insufficient 
buffer
             return "";
         }
     }

     // Allocate memory for userNameA
     scope(exit) userNameA.length = 0; // Ensure memory is 
released if an exception occurs
     userNameA.length = userNameSize;

     // Retrieve the user name by calling GetUserNameA
     if (GetUserNameA(userNameA.ptr, &userNameSize)) {
         // Successfully retrieved the user name using ANSI 
version, convert it to a string
         return to!string(userNameA);
     }

     // Both GetUserNameW and GetUserNameA failed, return an empty 
string
     return "";
}

/**
  * The entry point of the application.
  */
void main(string[] args) {
     string username = getSafeUsername();
     if (args.length > 1 && args[1] == "print") {
		write(username);
     } else if (!username.empty){
		writeln("Logged-in user name: ", username);

	} else {
         writeln("Failed to retrieve the user name.");
     }
}

```