The contents of file.txt are:
5 3
6 4
7 1
10 5
11 6
12 3
12 4
Where 5 3
is a coordinate pair.
How do I process this data line by line in C++?
I am able to get the first line, but how do I get the next line of the file?
ifstream myfile;
myfile.open ("file.txt");
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))
{
std::istringstream iss(line);
int a, b;
if (!(iss >> a >> b)) { break; } // error
// process pair (a,b)
}
You shouldn't mix (1) and (2), since the token-based parsing doesn't gobble up newlines, so you may end up with spurious empty lines if you use getline()
after token-based extraction got you to the end of a line already.