Question

I am trying to write program for parsing and processing text file.
After not being successful with implementing sscanf i decided to try stringstream.

I have vector of strings containing data separated by spaces, like:

some_string another_string yet_another_string VARIABLE_STRING_NO_1
next_string

I wrote code and expected result would be:

Counter: 4
Variable number 1 : VARIABLE_STRING_NO_1
Variable number 2 : VARIABLE_STRING_NO_2
Variable number 3 : VARIABLE_STRING_NO_3
Variable number 4 : VARIABLE_STRING_NO_4

but instead i get:

Counter: 4
Variable number 1 : VARIABLE_STRING_NO_1
Variable number 2 : VARIABLE_STRING_NO_1
Variable number 3 : VARIABLE_STRING_NO_1
Variable number 4 : VARIABLE_STRING_NO_1

Can anyone push me in right direction please? (eg. use other container instead of vector, change method to… etc)

Also what if VARIABLE_STRING contains 2 sub-strings with space inbetween? That is possible in my data.

Sample code:

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

int main()
{
    vector<string> vectorOfLines, vectorOfData;

    vectorOfLines.push_back("some_string another_string yet_another_string VARIABLE_STRING_NO_1 next_string");
    vectorOfLines.push_back("some_string another_string yet_another_string VARIABLE_STRING_NO_2 next_string");
    vectorOfLines.push_back("some_string another_string yet_another_string VARIABLE_STRING_NO_3 next_string");
    vectorOfLines.push_back("some_string another_string yet_another_string VARIABLE_STRING_NO_4 next_string");

    string data = "", trash = "";
    stringstream token;

    int counter = 0;

    for( int i = 0; i < (int)vectorOfLines.size(); i++ )
    {
        token << vectorOfLines.at(i);
        token >> trash >> trash >> trash >> data >> trash;
        vectorOfData.push_back(data);                       //  wrong method here?
        counter++;                                          //  counter to test if for iterates expected times
    }

    cout << "Counter: " << counter << endl;

    for( int i = 0; i < (int)vectorOfData.size(); i++ )
    {
        cout << "Variable number " << i + 1 << " : " << vectorOfData.at(i) << endl;
    }

    return 0;
}

Excuse my newbie question but after trying different approaches for last 5 days, I got to the point of swearing and getting discourages to continue learning.
Yes I’m very new to C++.
I’ve successfully done the same program in PHP (being total newbie in that too) and it seems like C++ is much, much harder to do.

Answer 1

You want to reset you string stream after reading an individual. From the looks of it, the string stream you are using goes into a fail state. At this point it won’t except any further input until the state gets clear(). Also, you should always verify that you read was successful. That is, I would start the body of your loop something like this:

token.clear();
token.str(vectorOfLines[i]);
if (token >> trash >> trash >> trash >> data >> trash) {
    process(data);
}
else {
    std::cerr << "failed to read '" << vectorOfLines[i] << "\n";
}

I would also just use an std::istringstream.