How to read-write into/from text file with comma separated values

Step 1: Don't do this:

while(!file.eof())
{
    getline(file,line);
    numlines++;
}
numline--; 

The EOF is not true until you try and read past it. The standard pattern is:

while(getline(file,line))
{
    ++numline;
}

Also note that std::getline() can optionally take a third parameter. This is the character to break on. By default this is the line terminator but you can specify a comma.

while(getline(file,line))
{
    std::stringstream   linestream(line);
    std::string         value;

    while(getline(linestream,value,','))
    {
        std::cout << "Value(" << value << ")\n";
    }
    std::cout << "Line Finished" << std::endl;

}

If you store all the values in a single vector then print them out using a fixed width. Then I would do something like this.

struct LineWriter
{
        LineWriter(std::ostream& str,int size)
                :m_str(str)
                ,m_size(size)
                ,m_current(0)
        {}

        // The std::copy() does assignement to an iterator.
        // This looks like this  (*result) = <value>;
        // So overide the operator * and the operator = to
        LineWriter& operator*() {return *this;}   
        void operator=(int val)
        {
                ++m_current;
                m_str << val << (((m_current % m_size) == 0)?"\n":",");
        }

        // std::copy() increments the iterator. But this is not usfull here
        // so just implement too empty methods to handle the increment.
        void operator++()       {}
        void operator++(int)    {}

        // Local data.
        std::ostream&           m_str;
        int const               m_size;
        int                     m_current;
};

void printCommaSepFixedSizeLinesFromVector(std::vector const& data,int linesize)
{
    std::copy(data.begin(),data.end(),LineWriter(std::cout,linesize));
}

here I m posting the code for CSV read as well as write code. I have checked its working fine.

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

void readCSV(istream &input, vector< vector<string> > &output)
{
   string csvLine;
    // read every line from the stream
    while( getline(input, csvLine) )
    {
            istringstream csvStream(csvLine);
           vector<string> csvColumn;
            string csvElement;
            // read every element from the line that is seperated by commas
            // and put it into the vector or strings
            while( getline(csvStream, csvElement, ',') )
            {
                    csvColumn.push_back(csvElement);
            }
            output.push_back(csvColumn);
    }
}

int main()
{
    ofstream myfile;
    string a;
    fstream file("b.csv", ios::in);
    myfile.open ("ab.csv");
    if(!file.is_open())
    {
           cout << "File not found!\n";
            return 1;
    }
    // typedef to save typing for the following object
    typedef vector< vector<string> > csvVector;
    csvVector csvData;

    readCSV(file, csvData);
    // print out read data to prove reading worked
    for(csvVector::iterator i = csvData.begin(); i != csvData.end(); ++i)
    {
            for(vector<string>::iterator j = i->begin(); j != i->end(); ++j)
            {
          a=*j;
                  cout << a << " ";
          myfile <<a<<",";

 }
 myfile <<"\n";
 cout << "\n";
 }
 myfile.close();
 system("pause");

}