Parse links from HTML <a> tags from an input file

linksParser.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <regex>
using namespace std;

void parseLinks(string file) {
	// Pattern of a HTML link tag
	string patt = "(<a href\\s*=\\s*)(\")([^<\"]*)";
	// Regex object to match this pattern
	regex link (patt);
	// Create an empty iterator so that we will know when should we stop
	const sregex_token_iterator end;
	// This is used to determinate wheter there were matches and print messages accordingly
	bool matchesFound = false;
	// This is used to only capture the third group, aka the address
	vector<int> v;
	// This makes it the 3rd group
	v.push_back(3);
	for (sregex_token_iterator i(file.begin(), file.end(), link, v);
		i != end;
		++i)
	{
		// If it's the first match, print a message and update the boolean var
		if(!matchesFound) {
			cout << "Matches found:" << endl;
			matchesFound = true;
		}
		// Print a match
		cout << (*i).str() << endl;
	}
	// If no matches were found, print a message
	if(!matchesFound) {
		cout << "No matches found." << endl;
	}
}

int main () {
	string file;
	string line;
	string filename;
	// Get a filename from the user
	cout << "Please enter a file name:" << endl;
	cin >> filename;
	ifstream myfile (filename);
	// If the file is valid, open it
	if (myfile.is_open()) {
		// Read the lines into a string
		while ( getline (myfile,line) ) {
			file += line + "\n";
		}
		// Close the file
		myfile.close();
		// Find all the links in the file
		parseLinks(file);
	}
	// If the filename is not valid, print an error
	else
		cout << "Unable to open file" << endl; 
}