How to handle missing values in C++ using strtok function?

[Man4ish]

Hi,

I am parsing one tab delimited file with some missing values. When i use the strtok function, I can not get the values based on index in vector. The code shown below explains my pblm.

#include <iostream.h>
#include <string.h>
#include <vector.h>
 
using namespace std;
 
int main ()
{
  char str[] ="XYZ 2 a sample      data";
  char * pch;
  vector <char*> vec;
  pch = strtok (str,"\t");
  while (pch != NULL)
  {
    vec.push_back(pch);
    pch = strtok (NULL, "\t");
  }
  cout << "Fifth null element is "<<vec[4]<<"\n";
  return 0;
}

In the above code i am supposed to get null value (missing) but i am getting "data" as output. How can i handle missing values?
Thansk in advance.

[Banfa]

Look at your string, "XYZ 2 a sample data", it has 5 tokens

1. XYZ
2. 2
3. a
4. sample
5. data

So of course vec[4] wont be NULL. Worst than that, since you don't set the size of your vector if it had less than 5 strings vec[4] wouldn't be NULL, it would be an out of bounds memory access, or if you used vec.at(4) which checks index boundaries you would get an exception.

I can begin to describe how bad a function strtok is. You should avoid using it at all costs. Get used to doing something else because if you ever program in a multi-threaded environment you will need to avoid it because it is not at all re-entrant or thread safe.

A std::istringstream should work just as well.

As to your problem, since you have not said what data format you are expecting in your string and since you do not have a designed way to read that format it is hard to give further advice.