ios::out opens the file for writing. ios::binary makes sure the data is read or written without translating new line characters to and from \r\n on the fly. In other words, exactly what you give the stream is exactly what’s written.
You are writing to file the vector structure, not its data buffer. Try change writing procedure to: ofstream fout(“data.dat”, ios::out | ios::binary); fout.write((char*)&student[0], student.size() * sizeof(Student)); fout.close(); And instead of calculation size of vector from file size, it’s better write vector size (number of objects) before. In the case you can write to the same … Read more
You should add fstream::out to open method like this: file.open(“test.txt”,fstream::out); More information about fstream flags, check out this link: http://www.cplusplus.com/reference/fstream/fstream/open/
Simplest form: std::string line; std::vector<std::string> myLines; while (std::getline(myfile, line)) { myLines.push_back(line); } No need for crazy c thingies 🙂 Edit: #include <iostream> #include <fstream> #include <string> #include <vector> int main() { std::string line; std::vector<std::string> DataArray; std::vector<std::string> QueryArray; std::ifstream myfile(“OHenry.txt”); std::ifstream qfile(“queries.txt”); if(!myfile) //Always test the file open. { std::cout<<“Error opening output file”<< std::endl; system(“pause”); return … Read more
Probably the best way is to read the entire file’s contents into a string, which can be done very easily using ifstream’s rdbuf() method: std::ifstream in(“myfile”); std::stringstream buffer; buffer << in.rdbuf(); std::string contents(buffer.str()); You can then use regular string manipulation now that you’ve got everything from the file. While Tomek was asking about reading a … Read more
Use iterators. std::vector<int> lines; // fill std::size_t const half_size = lines.size() / 2; std::vector<int> split_lo(lines.begin(), lines.begin() + half_size); std::vector<int> split_hi(lines.begin() + half_size, lines.end()); Since iterator ranges represent half open ranges [begin, end), you don’t need to add 1 to the second begin iterator: lines.begin() + half_size isn’t copied to the first vector. Note that things … Read more
You can try this: #include <fstream> int main () { std::ofstream myfile; myfile.open (“example.txt”); myfile << “Writing this to a file.\n”; myfile.close(); return 0; }
You’re specifying std::fstream::in in your call to fstream::open(). This is known to force it to require an existing file. Either remove std::fstream::in from your mode argument, or specify std::fstream::trunc in addition to the other flags.
This is one of my favorite tuck-away functions I keep on hand for multiple uses. #include <sys/stat.h> // Function: fileExists /** * Check if a file exists * * @param[in] filename – the name of the file to check * * @return true if the file exists, else false */ bool fileExists(const std::string& filename) { … Read more
I would probably go with: ifstream my_file(“test.txt”); if (my_file.good()) { // read away } The good method checks if the stream is ready to be read from.