How do I read an entire file into a std::string in C++?

Question

How do I read a file into a std::string, i.e., read the whole file at once?

Text or binary mode should be specified by the caller. The solution should b

Answer 1

Since this seems like a widely used utility, my approach would be to search for and to prefer already available libraries to hand made solutions, especially if boost libraries are already linked(linker flags -lboost_system -lboost_filesystem) in your project. Here (and older boost versions too), boost provides a load_string_file utility:

#include 
#include 
#include 

int main() {
    std::string result;
    boost::filesystem::load_string_file("aFileName.xyz", result);
    std::cout << result.size() << std::endl;
}

As an advantage, this function doesn't seek an entire file to determine the size, instead uses stat() internally. As a possibly negligible disadvantage though, one could easily infer upon inspection of the source code: string is unnecessarily resized with '\0' character which are rewritten by the file contents.