// This program shows how C++-based file I/O works. // It will print a file to the screen two times. // included so we can use cout #include <iostream> // file I/O #include <fstream> // cstdlib is where exit() lives #include <cstdlib> using namespace std; // we want to use parameters int main(int argc, char** argv) { // verify the correct number of parameters if (argc != 2) { cout << "Must supply the input file name as the one and only parameter" << endl; exit(1); } // attempt to open the supplied file // ifstream stands for "input file stream" ifstream file(argv[1]); // if the file wasn't found, output an error message and exit if (!file.is_open()) { cout << "Unable to open '" << argv[1] << "' for reading" << endl; exit(2); } // read in characters one by one, until reading fails (we hit the end of the file) char g; while (file.get(g)) { cout << g; } // a nice pretty separator cout << "----------------------------------------" << endl; // once we hit the end of the file we are marked as "failed", so clear that // then "seek" to the beginning of the file to start again file.clear(); // Clears the _state_ of the file, not its contents! file.seekg(0); // Read the file again, and print to the screen while (file.get(g)) { cout << g; } // close the file file.close(); return 0; }