Read from file line by line and parse to vector a lot of ints in c++ -

i have seen lot of similar posts regarding similar cases case bit different. i'm newbie c++, appreciated.

i have large file full of lines full of integers. each number separated blank spaces. need diferent lines stay seperate, don't want read file on 1 go. want read line line , parse each line in vector of integers. code i've got this:

int main () {   string line;   ifstream myfile;   myfile.open ("numbers.txt");   vector<int> vec1;   int const2=0;   int a;   while ( getline (myfile,line) ){ // understand reads line                                     // line , stores string "line"     while (line >> a){  // part 1 can't right,                          // want push_back every int                         // string vec1 doesn't work       vec1.push_back(a);        // more stuff     }     // more stuff   }   myfile.close();      return 0; } 

here c++11 way (use -std=c++0x g++ or clang++), can google each function don't know. using back_inserter , istream_iterator cleaner while/for loop come on own. using deque in context more efficient. can take file name main input.

#include <algorithm> #include <iterator> #include <iostream> #include <sstream> #include <fstream> #include <string> #include <deque>  int main() {     const std::string filename = "/path/to/file.txt";      std::string    line_buf;     std::ifstream  file( filename );      std::deque< std::deque<int> > parsed_data;     if (file) while ( std::getline(file,line_buf) )     {         std::deque<int>    parsed_line;         std::stringstream  ss( line_buf );          std::copy( std::istream_iterator<int>(ss), std::istream_iterator<int>(), std::back_inserter(parsed_line) );          parsed_data.emplace_back();         parsed_data.back().swap( parsed_line );     } } 

to check result in console, can use function

#include <cstdio> void show_result( const std::deque< std::deque<int> >& data ) {     size_t line_count = 0;     ( auto& line: data )     {         printf( "line %02ld: ", ++line_count );         ( auto& num: line )             printf( "%d ", num );             printf( "\n" );     } }