CODEWITHSUNDEEP
c++file-iodelimitergetline
TheOneTrueSign
TheOneTrueSign

Reputation: 149

Grabbing data from file using getline

So I have a file that has multiple columns of data like this:

1 2 3
4 5 6
7 8 9
etc...

And I'm traversing through this file with a while loop trying to store the data in a vector as I go along. But when I use a delimiter to deal with the spaces in between the data it only reads the first line and stops. The code for the while loop is as follows:

while(getline(infile,content, ' '))
{
 double temp = atof(content.c_str();
 cout << "value storing is: " << temp << endl;
 data.push_back(temp);
}

Using the data above with this code I just get "1 2 3" as the output. So i'm not sure where I'm going wrong with this.

The column the numbers are in are also important when I crunch the data later. For example, every iteration of the while loop will add a counter and every time it goes to a new line will be another counter so with that i can figure out how many lines I have so when I need to compute something I can use i%(columnNumber) to grab that value.

Thanks for any light anyone can shed on my situation.

Upvotes: 0

Views: 151

Answers (1)

Matt
Matt

Reputation: 437

It's because there are no spaces after a new line.

This is what the file looks like (to std::getline())

1 space 2 space 3 newline 4 space 5 space 6 newline 7 space 8 space 9

I can't reproduce "1 2 3" as output. When I run your code, I get 

value storing is: 1
value storing is: 2
value storing is: 3
value storing is: 5
value storing is: 6
value storing is: 8
value storing is: 9

where my test file looks like this:

1 2 3
4 5 6
7 8 9

To fix the problem, try doing something like this: 

int main()
{
    std::ifstream in("test");

    std::string content;
    std::vector<int> data;

    while (getline(in, content))
    {
        std::stringstream linestream(content);

        int value;
        // Read an integer at a time from the line
        while(linestream >> value)
        {
            // Add the integers from a line to a 1D array (vector)
            data.push_back(value);
            std::cout << "value storing is: " << value << std::endl;
        }
    }

}

Upvotes: 2

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