Question

I have a piece of code in which I need to use a string with both ifstream::open and CreateProcess, something like

//in another file
const char* FILENAME = "C:\\...blah blah\\filename.bat";

---

// in main app
std::ifstream is;
is.open(FILENAME);
// ...do some writing
is.close();

STARTUPINFO si;
PROCESS_INFORMATION pi;

ZeroMemory( &si, sizeof(si) );
si.cb = sizeof(si);
ZeroMemory( &pi, sizeof(pi) );

std::string cmdLine = "/c " + FILENAME;

if( !CreateProcess( "c:\\Windows\\system32\\cmd.exe", 
    cmdLine.c_str(), NULL, NULL, FALSE, 0, NULL, NULL, &si, &pi) ) 
{       
    return GetLastError();
}

CreateProcess requires a LPCWSTR, so to use the string with CreateProcess I would need to declare the filename and ‘cmdLine’ as std::wstring, but ifstream::open doesn’t take wide strings…I can’t figure a way to get around this. I always seem to run into problems with unicode vs multibyte strings.

Any ideas?
Thanks.

Answer 1

I’m assuming you defined UNICODE. You can change STARTUPINFO to STARTUPINFOA and CreateProcess to CreateProcessA and it should work fine (it did for me).

I don’t think it’ll like the + operation though. Explicitly convert one char array to a string.

std::string cmdLine = (std::string)"/c " + FILENAME;

Finally, you’re going to need quotes around the beginning and end of FILENAME if it has a space.

const char FILENAME = "\"C:\\Program Files\\Company\\Program\\program.exe\"";
                        ^           ^                                     ^

Edit:
Try putting this below your string declaration:

char charCmdLine [MAX_PATH + 3]; //"/c " is 3 extra chars
strncpy (charCmdLine, cmdLine.c_str(), MAX_PATH + 3);

Then, use charCmdLine in CreateProcess instead of cmdLine.c_str().