Trying to create a loop that creates csv files

**airesore** · 09-30-2011

I'm trying to create a loop that creates csv files.

It's quite simple, however fileout.open() or ofstream fileout () gives me an error when i tired to put a string inside the parameter.

I tired both ways and they both doesn't work.

Code:

int x = 5;
//loop stuff to get x

         int x = 5;
         std::string s;
         std::stringstream out;
         out << x;
         s = out.str();
         s += ".csv";
         ofstream onFile (s);

Code:

int x = 5;
//loop stuff to get x

         std::string s;
         std::stringstream out;
         out << x;
         s = out.str();

     s += ".csv";
     ofstream fileout ;
     fileout.open (s) ;

If you could help me, it would be nice. Thanks

**rmatze** · 09-30-2011

You almost had it.

Code:

#include <fstream>
#include <sstream>
using namespace std;

int main() {
    
    int x = 0;
    ofstream myfile;

    while(x < 5)
    {
        string s;
        stringstream out;
        out << x;
        s = out.str();
        s += ".csv";
        myfile.open(s.c_str());
        myfile.close();
        x++;
    }

    return 0;
}

**airesore** · 09-30-2011

thanks rmatze

Edit:can someone explain what's c_str() is about? Sorry i'm quite new in C++ and i'm trying to port my java skills in C++. I'm not really getting why C++ just can't process a string, but can process it if it has c_str().

I tired googling it, but it just say that it's a member function yields a pointer to the first element of an array whose elements correspond to the bytes in the original string and this array has a 0 at the offset of the length.

It would be nice if someone could put it in a more easier explaination.

**whiteflags** · 09-30-2011

There are at least two string types in C++, and those are the older char* strings from C and the std::string class. Back in the seventies there was no std::string, along with the rest of the stl, and that was the case for a while, but people were still using C++ in that time. So you have this awkward time period where people used their own string implementations and the only standard one was char*.

So that is why open() takes a char*.

But recently, C++11, the newest standard, added an open() that uses std::string, so try compiling under the newest standard: i.e. find the setting that enables C++11 features in your compiler or IDE.

If you're asking what a char* string is, it is a sequence of characters terminated by 0. The char* actually points to the zeroth character.

HTH

**phantomotap** · 09-30-2011

Eighties. ^_^

Before that there was "C with classes".

Soma

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