Update: GetUserName by print to stdout
Main function has been updated with `string[] args` and a new
feature:
```
if (args.length > 1 && args[1] == "print") {
write(username);
}
```
Usage:
`WindowsGetUserName.exe print`
Demonstration
WindowsGetUserName.d
```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, )) {
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, )) {
// 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, )) {
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, )) {
// 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.");
}
}
```
