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
This is the perfect situation to use a facet. A custom version of the codecvt facet can be imbued onto a stream. So your usage would look like this: int main() { /* Imbue std::cout before it is used */ std::ios::sync_with_stdio(false); std::cout.imbue(std::locale(std::locale::classic(), new IndentFacet())); std::cout << “Line 1\nLine 2\nLine 3\n”; /* You must imbue a … Read more
You cannot insert in the middle of the file. You have to copy the old file to a new file and insert whatever you want in the middle during copying to the new file. Otherwise, if you intend to overwrite data/lines in the existing file, that is possible by using std::ostream::seekp() to identify the position … Read more
I think the previous answers are misleading. fstream is a proper RAII object, it does close automatically at the end of the scope, and there is absolutely no need whatsoever to call close manually when closing at the end of the scope is sufficient. In particular, it’s not a “best practice” and it’s not necessary … Read more
First, make an ifstream: #include <fstream> std::ifstream infile(“thefile.txt”); The two standard methods are: Assume that every line consists of two numbers and read token by token: int a, b; while (infile >> a >> b) { // process pair (a,b) } Line-based parsing, using string streams: #include <sstream> #include <string> std::string line; while (std::getline(infile, line)) … Read more