C ++ argument type for ifstream :: open ()

Question

What type should I make my file name use it as an argument to ifstream.open() ?

 int main(int argc, char *argv[]) { string x,y,file; string file = argv[1]; ifstream in; in.open(file); in >> x; in >> y; ... 

Using this code, I get the following error:

 main.cpp|20|error: no matching function for call to 'std::basic_ifstream<char, std::char_traits<char> >::open(std::string&)'| gcc\mingw32\4.4.1\include\c++\fstream|525|note: candidates are: void std::basic_ifstream<_CharT, _Traits>::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]| 

UPDATE:

i get this error

Answer 1

The constructor accepts const char * (http://www.cplusplus.com/reference/iostream/ifstream/ifstream/), so you should do it like this:

 in.open(argv[1]); 

or if you really want to use the file line variable then

 in.open(file.c_str());