Read File line by line to variable and loop

Question

I have a phone.txt like:

09236235965
09236238566
09238434444
09202645965
09236284567
09236235965
..and so on..

How can I process this data

Answer 1

Simple. First, note that you want an ifstream, not an ofstream. When you're reading from a file, you're using it as input - hence the i in ifstream. You then want to loop, using std::getline to fetch a line from the file and process it:

std::ifstream file("phone.txt");
std::string phonenum;
while (std::getline(file, phonenum)) {
  // Process phonenum here
  std::cout << phonenum << std::endl; // Print the phone number out, for example
}

The reason why std::getline is the while loop condition is because it checks the status of the stream. If std::getline fails in anyway (at the end of your file, for example), the loop will end.