can not write data into file using c++

Question

ofstream osCtrs("cts.txt",ios::out);
if (osCtrs.is_open()){
    for(unsigned ci = 0; ci < k; ci++){
        KMpoint& x =  ctrs[ci];
        for (unsigned di = 0; di < dim; di++)
        {
            //osCtrs << x[di];
            osCtrs << "what is happening?";
        }
    }
    osCtrs.close();
}

anything wrong? file is created, but always empty,

Answer 1

The code works fine for me, given positive values for k and dim. Are you sure they're both non-zero? If either one is 0 or less, the program will never enter the inner loop where you're actually outputting stuff. Try setting a breakpoint and stepping through the code to see what's happening.

Also, you don't need to specify ios::out for an ofstream, it's implied.