tail.cpp

#include <iostream>
#include <fstream>
#include <chrono>
#include <thread>
#include <sstream>

void tail(std::ifstream& f)
{
    std::uint64_t lineCount = 0;
    auto sleepTime = std::chrono::seconds(0);

    while(true)
    {
        std::stringstream line;

        while(true)
        {
            std::this_thread::sleep_for(sleepTime);

            char c;
            f.clear();
            f.get(c);

            if(f.eof())
            {
                sleepTime = std::chrono::seconds(1);
                continue;
            }

            sleepTime = std::chrono::seconds(0);

            if(c == '\n')
            {
                std::cout << lineCount++ << ':' << line.str() << std::endl;
                break;
            }
            else
            {
                line << c;
            }
        } 
    }
}

int main(int argc, char** argv)
{
    if(argc != 2)
    {
        std::cout << "usage: dail <filename>" << std::endl;
        return -1;
    }

    std::ifstream f(argv[1]);
    if(!f.is_open())
    {
        std::cout << "File could not be opened" << std::endl;
        return -2;
    }

    tail(f);

    return 0;
}