Loop your way there. #include <fstream> #include <limits> std::fstream& GotoLine(std::fstream& file, unsigned int num){ file.seekg(std::ios::beg); for(int i=0; i < num – 1; ++i){ file.ignore(std::numeric_limits<std::streamsize>::max(),’\n’); } return file; } Sets the seek pointer of file to the beginning of line num. Testing a file with the following content: 1 2 3 4 5 6 7 8 … Read more
You can use std::getline : #include <fstream> #include <string> int main() { std::ifstream file(“Read.txt”); std::string str; while (std::getline(file, str)) { // Process str } } Also note that it’s better you just construct the file stream with the file names in it’s constructor rather than explicitly opening (same goes for closing, just let the destructor … Read more
The short answer is no. The reason, is because the std::fstream is not required to use a FILE* as part of its implementation. So even if you manage to extract file descriptor from the std::fstream object and manually build a FILE object, then you will have other problems because you will now have two buffered … Read more
I was trying to find the final word on mmap / read performance on Linux and I came across a nice post (link) on the Linux kernel mailing list. It’s from 2000, so there have been many improvements to IO and virtual memory in the kernel since then, but it nicely explains the reason why … Read more
From the answer given by Éric Malenfant: AFAIK, there is no way to do this in standard C++. Depending on your platform, your implementation of the standard library may offer (as a nonstandard extension) a fstream constructor taking a file descriptor as input. (This is the case for libstdc++, IIRC) or a FILE*. Based on … Read more
Just follow closely the chain of events. Grab 10 Grab 20 Grab 30 Grab EOF Look at the second-to-last iteration. You grabbed 30, then carried on to check for EOF. You haven’t reached EOF because the EOF mark hasn’t been read yet (“binarically” speaking, its conceptual location is just after the 30 line). Therefore you … Read more
you forgot to add ‘\0’ char in zero terminated char array, after you replaced value with index 2.
You can use the constructor to specify the filename: ifstream inputFile(“data.txt”); See the details for std::basic_ifstream (constructor). explicit basic_ifstream( const char* filename, std::ios_base::openmode mode = ios_base::in ); First, performs the same steps as the default constructor, then associates the stream with a file by calling rdbuf()->open(filename, mode | std::ios_base::in) (see std::basic_filebuf::open for the details on … Read more