Read a file backwards?

c++

Solution

As per comment, a possible (quite simple) alternative would be read the lines into a `vector`. For example:

#include <iostream>
#include <fstream>
#include <string>
#include <vector>

int main()
{
    std::ifstream in("main.cpp");

    if (in.is_open())
    {
        std::vector<std::string> lines_in_reverse;
        std::string line;
        while (std::getline(in, line))
        {
            // Store the lines in reverse order.
            lines_in_reverse.insert(lines_in_reverse.begin(), line);
        }
    }
}

EDIT:

As per jrok's and Loki Astari's comments, `push_back()` would be more efficient but the lines would be in file order, so reverse iteration (`reverse_iterator`) or `std::reverse()` would be necessary:

    std::vector<std::string> lines_in_order;
    std::string line;
    while (std::getline(in, line))
    {
        lines_in_order.push_back(line);
    }

Problem

Is there a way to read a file backwards, line by line, without having to go through the file from the beginning to start reading backwards?

Original source