Simple C++ program to show how to count a specific word in a text file

word-counter.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <iterator>

int main()
{
    std::string filename;
    std::cout << "Enter filename: ";
    std::cin >> filename;

    std::string word_to_search_for;
    std::cout << "Enter word to search for: ";
    std::cin >> word_to_search_for;

    auto tolower = [](std::string& s)
    {
        std::transform(begin(s), end(s), begin(s), ::tolower);
    };

    tolower(word_to_search_for);

    // Open the file
    std::ifstream file_to_read_from(filename);
    if (!file_to_read_from)
    {
        std::cerr << "Could not open file \"" << filename << "\"\n";
        return 1;
    }

    // Now read the file, one word at a time, into a vector
    // (Need to do it this way since otherwise we will have the most vexing parse)
    std::vector<std::string> all_words = std::vector<std::string>(
        std::istream_iterator<std::string>(file_to_read_from),
        std::istream_iterator<std::string>());

    // Convert all read words into lower-case
    std::for_each(begin(all_words), end(all_words), tolower);

    // And count all the words matching the one requested
    long count = std::count(begin(all_words), end(all_words), word_to_search_for);

    std::cout << "The word \"" << word_to_search_for << "\" was found " << count << " times\n";
}

Needs C++11 since I use lambdas.