How to write vector values to a file

Question

I have a large vector.

The ways that I use multiply the run-time of the program hugely. The first is write all values to a string as they are calculated using stringstreams and later write the string to a file. The other method is to make a long string after the fact and write that to the file. However, both of these are very slow.

Is there a way to just write the vector's values to the text file immediately with line breaks?

Answer 1

Using std::ofstream, std::ostream_iterator and std::copy() is the usual way to do this. Here is an example with std::strings using C++98 syntax (the question was asked pre-C++11):

#include <fstream> #include <iterator> #include <string> #include <vector>  int main() {     std::vector<std::string> example;     example.push_back("this");     example.push_back("is");     example.push_back("a");     example.push_back("test");      std::ofstream output_file("./example.txt");     std::ostream_iterator<std::string> output_iterator(output_file, "\n");     std::copy(example.begin(), example.end(), output_iterator); }