Read a Whole File into a std::string (C++17)

Easily load file contents into a string with just 10 lines of code using C++17.

Introduction

Reading the entire content of a file into a string is a common task in programming. With C++17, this can be accomplished succinctly using standard library features. In this guide, we will walk through a simple 10-liner solution to achieve this.

Step-by-Step Guide

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

std::string readFileIntoString(const std::string& filePath) {
    std::ifstream file(filePath, std::ios::in | std::ios::binary);
    if (!file) {
        throw std::runtime_error("Could not open the file");
    }
    std::string contents;
    file.seekg(0, std::ios::end);
    contents.resize(file.tellg());
    file.seekg(0, std::ios::beg);
    file.read(&contents[0], contents.size());
    if (!file) {
        throw std::runtime_error("Failed to read the entire file");
    }
    return contents;
}

    

Conclusion

Reading a whole file into a string in C++17 can be efficiently done with just 10 lines of code. By using the standard library's file stream classes, you can handle file operations effectively and concisely. This method ensures that the entire file is read into memory as a string, making it easy to manipulate or process further.