How to parse a string in C++?

Since all you need are individual characters (not context-dependent multicharacter tokens for example), there is nothing special to do. Simply iterate through the string character-by-character and write any chracter that matches your requirements to the output file:

#include <iostream>

#include <fstream>

#include <string>

#include <cctype>

#include <boost/asio.hpp>

int main()

{

     boost::asio::ip::tcp::iostream s("www.google.com", "http");

     if(!s)

         std::cout << "Could not connect to www.google.com\n";

     s << "GET / HTTP/1.0\r\n"

          << "Host: www.google.com\r\n"

          << "Accept: */*\r\n"

          << "Connection: close\r\n\r\n" ;

     std::ofstream out("output.txt");

     for(char c; s.get(c); )

     {

          if(std::isdigit(c) || c == ',' || c == '-' || c == '%' || c == '.')

               out.put(c);

     }

}

test (without webpage access) https://ideone.com/0qgam

If you need something more complicated, formatted input (stream >> variable and getline(stream, string, delimiter)) can help with breaking the text into individual multicharacter tokens, regular expressions (#include <regex>) can deal with many context-dependent tasks, and full-fledged parser libraries such as boost.spirit can deal with arbitrarily complex grammars.

mmk...

if you want to take things out of it (numbers commas hypens etc...) do this:

I assume that you have all of the text in a single string (named source) for this.

string result;

vector<char> result_pre_parse(); /*this is a vector object, you need to #include <vector>*/

char[] source_array = source.c_str(); /*preparse it for faster output in case if its very big*/

for(int i = 0; i<source.size(); i++)

{

switch(source_array[i])

{

case ','://put all of your characters like so, without breaks

case '.':

case '1':

case '2'://etc....

result_pre_parse.push_back(source_array[i]);

break;

default:

break;

}//switch

}//for

result = result_pre_parse; /* this should work, if it doesnt, find some way to change a vector into an array, should be easier*/

/*do something with the result string, like write to a text file*/