data.txt

This is some data.
42
I am a goat. (This is 13 percent untrue.)

ExploringFiles.cpp

#include <iostream>
#include <filesystem>
#include <fstream>
#include <vector>

int main() {
	std::cout << "CWD: " << std::filesystem::current_path() << "\n";

	std::ifstream inputFile{"data.txt"};

	if (!inputFile) {
		std::cerr << "There was an issue opening this file.\n";
	}

	// While Loop to Consume File Data Until EOF (End Of File)
	// Stream the data from the input stream into a string.
	// Delimited by spaces and newlines.
	// But why are we able to get into the loop once past EOF???
	std::cout << "\nSTREAM READING DELIMITED BY SPACES AND NEWLINES: \n\n";

	while (!inputFile.eof()) {
		// Loop until we reach the end of file.
		std::string data;
		inputFile >> data;
		std::cout << "##" << data << "##\n";
	}

	// inputFile.clear(); // Only needed if we have consumed an EOF... which we haven't.
	inputFile.seekg(0); // Set position in input sequence to 0. (g for get)

	std::cout << "\n\nLINE BY LINE READING OF THE SAME FILE: \n\n";

	while (!inputFile.eof()) {
		std::string line;
		std::getline(inputFile, line); // NOTE: line is an "out parameter"
		std::cout << "##" << line << "##\n";
	}

	std::cout << "\n\nREADING IN OUR NUMBERS:\n\n";

	std::ifstream numberFile{"numbers.csv"};

	if (!numberFile) {
		std::cerr << "There was an issue opening this file.\n";
	}

	std::vector<int> numbers;

	while (!numberFile.eof()) {
		int number;
		if (numberFile >> number) {
			// Did our integer read succeed?
			numbers.push_back(number); // Push the int into our vector.
		} else {
			// Looks like we read in either our delimiter or an unexpected char.
			numberFile.clear(); // Clear the fail bit, otherwise we can't read any further.
			char delimiter;
			numberFile >> delimiter; // Read in the character that triggered the read error.
			// Is it our delimiter?
			if (delimiter != ',') {
				// If not print it out to the standard error stream.
				std::cerr << "Read in bad char: [" << delimiter << "]\n";
			}
		}

	}

	std::cout << "\n\nTHE CONTENTS OF OUR NUMBERS VECTOR:\n\n";
	for (auto number : numbers) {
		std::cout << number << "\n";
	}

}

numbers.csv

93,23,2342,123,532
123,23423,8,87,123
1,2,3,4,5
10,9,8,7,6,5,4,3,2,1