How do they work: String streams

[joeriMJ]

Hi,

I've been breaking my head over this for quite a while now and can't figure out how and even more important why this code works.

this is the input file:
1 word1 2
2 word2 3
3 word3 4

this is the output file:
word1 1 2
word2 2 3
word3 3 4

#include <fstream>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <string>
using namespace std;

int main(void)
{
	ifstream infile("infile.str");
	if(infile)
	{
		char buffer[81];
		cout<< endl << "file information:" << endl;
		while(infile.getline(buffer, 81, '\n'))
		{
			istringstream instr(buffer, istringstream::in);
			int number1, number2;
			char word[50];
			instr>> number1 >> word >> number2;
			cout<< word << setw(10) << number1 << setw(10) << number2 << endl;
		}
	}
	else cerr<< endl << "Error opening: infile.str";
	infile.close();

	return 0;
}

I'm having trouble understanding how this line works:
instr>> number1 >> word >> number2;

Is it defaul behavior for the >> operator to have a space character being the spacing character?

What if I would be working with a csv file, so the seperator for the field would be a "," ? Could I accomplish splitting a line into variables using the above method?

[Bazzy]

>> divides strings with whitespaces ( ' ', '\n', '\r', '\t', '\v' ) and numbers with non-numerical characters http://www.cplusplus.com/reference/iostream/istream/operator%3E%3E/
If you want to divide stuff with something else, you should use getline
http://www.cplusplus.com/reference/iostream/istream/getline/
http://www.cplusplus.com/reference/string/getline/

[joeriMJ]

So say that I have the same input file, except the seperator is a comma. Would this code be correct to get the values into seperate variables?

instr.getline(number1, sizeof(int), ',');
instr.getline(word, 50, ',');
instr.getline(number2, sizeof(int), ',');

I suppose the rest of the code is still correct.

[joeriMJ]

Just found out I had to use reinterpret_cast<char *>
Is this the way to go ? or should I stay away from reinterpret_cast ?

[Bazzy]

You should read to a string, create a new stringstream and read the integer
eg:

string numb_str;
getline ( instr, numb_str, ',' );
stringstream ( numb_str ) >> number1;

-You can also do that via C strings-