Parsing tab separated data

Question

I have a text file (~10GB) with the following format:

data1<TAB>data2<TAB>data3<TAB>data4<NEWLINE>

I want to scan through it and do processing only on data2. What is the best (fastest) way to extract data2 in C++.

EDIT: Added NEWLINE

Answer 1

Read the file line by line. For each line, split on the tab. That will leave you with an array containing the fields, allowing you to work with the second field (data2).

Answer 2

This sounds like a job for a higher level tool like shell utilities:

cut -f2           # from stdin
cut -f2 <my_file  # from file

But nonetheless, you can do that with C++ as well:

void parse(std::istream& in)
{
    std::string word;
    while( in ) {
        std::cin >> word;  // throwaway 1
        std::cin >> word;  // data2
        process(word);
        std::cin >> word >> word;  // throwaway 3 and 4
    }
}

// ...
parse(std::cin);
std::ifstream file("my_file");
parse(file);