C++ Merge 2 Strings Together - c++

Question

I'm trying to create a simple text file to Desktop, but I get in the console : "Access is denied.". I do the same thing from the Comand Line and no error. If I where to print the path I would get :
"
C:/Users/Alex
(Here is a new line)
/Desktop/MyTextFile.txt
I know when I add a string to another string via += string, I get a space between the 2 strings. Any help would be apreciate !
string getClip() {
HANDLE clip;
string clip_text = "";
if (OpenClipboard(NULL))
{
clip = GetClipboardData(CF_TEXT);
clip_text = (char*)clip;
CloseClipboard();
return clip_text;
}
}
string getUser() {
system("echo %username% | clip");
string user = getClip();
return user;
}
void create_a_simple_txt_file() {
string username = getUser();
ostringstream path;
path << "C:/Users/" << username << "/Desktop/MyTextFile.txt";
system(("echo I successful Write something to my file > " + path.str()).c_str());
}
int main() {
create_a_simple_txt_file();
cin.get();
return 0;
}

Answer 1

The problem is the usage of system and the echo command:
system("echo %username% | clip");
The echo command adds a trailing newline, which is copied into the clipboard with the clip command, and you then get the full string including the newline with getClip.
You could simply fix this by not using system at all, and instead get the username with the GetUserName Windows API function:
std::string getUser()
{
char username[64];
// Use the ASCII version of the function
if (GetUserNameA(username, sizeof username))
{
return username;
}
// An error
std::cerr << "Error getting username: " << GetLastError() << '\n';
return "";
}

Answer 2

I would bet your problem is in the getUser() function, that is returning the username with a trailing newline, not the string concatenation (that, by the way, does NOT add a space).
EDITED after question being edited:
As I supposed, the problem is in your getUser() function, see "Some programmer dude" answer about why it is wrong and a possible solution, if you are running on Windows OS.
Another problem can be that you are trying to access the desktop folder of another user, and the user running your program does not have permissions on it.
Another suggestion: you may want to use the appropriate C++ functions or fstream to write to a file, instead of using system().

Answer 3

You are getting an access denied error because you are working on garbage data. The line
system(("echo I successful Write something to my file > " + path.str()).c_str());
creates a temporary string and gets a pointer to its underlying character array. But before the system() call is executed, the temporary string gets destroyed and the pointer becomes invalid.
If you replace your system call with a cout you can see what command you are actually trying to execute. For me it was something like Ó╣iwµ, which is neither a valid command not a valid directory name. Hence, the access denied.
To solve that problem, assign the temporary string to a variable until you have used it:
string s = ("echo I successful Write something to my file > " + path.str());
system(s.c_str());