read a file c 2b 2b

1// reading a text file
2#include <iostream>
3#include <fstream>
4#include <string>
5using namespace std;
6
7int main () {
8  string line;
9  ifstream myfile ("example.txt");
10  if (myfile.is_open())
11  {
12    while ( getline (myfile,line) )
13    {
14      //use line here
15    }
16    myfile.close();
17  }
18
19  else cout << "Unable to open file"; 
20
21  return 0;
22}

1#include <iostream>
2#include <fstream>
3using namespace std;
4
5ifstream file_variable; //ifstream is for input from plain text files
6file_variable.open("input.txt"); //open input.txt
7
8file_variable.close(); //close the file stream
9/*
10Manually closing a stream is only necessary
11if you want to re-use the same stream variable for a different
12file, or want to switch from input to output on the same file.
13*/
14_____________________________________________________
15//You can also use cin if you have tables like so:
16while (cin >> name >> value)// you can also use the file stream instead of this
17{
18 cout << name << value << endl;
19}
20_____________________________________________________
21//ifstream file_variable; //ifstream is for input from plain text files
22ofstream out_file;
23out_file.open("output.txt");
24
25out_file << "Write this scentence in the file" << endl;

1/ fstream::open / fstream::close
2#include <fstream>      // std::fstream
3
4int main () {
5
6  std::fstream fs;
7  fs.open ("test.txt", std::fstream::in | std::fstream::out | std::fstream::app);
8
9  fs << " more lorem ipsum";
10
11  fs.close();
12
13  return 0;
14}

1// io/read-file-sum.cpp - Read integers from file and print sum.
2// Fred Swartz 2003-08-20
3
4#include <iostream>
5#include <iomanip>
6#include <fstream>
7using namespace std;
8
9int main() {
10    int sum = 0;
11    int x;
12    ifstream inFile;
13    
14    inFile.open("test.txt");
15    if (!inFile) {
16        cout << "Unable to open file";
17        exit(1); // terminate with error
18    }
19    
20    while (inFile >> x) {
21        sum = sum + x;
22    }
23    
24    inFile.close();
25    cout << "Sum = " << sum << endl; 
26    return 0;
27}
28

1int a, b;
2    
3ifstream bd; 
4myfile.open("file.txt");
5
6if (myfile.is_open())
7	while (bd >> a >> b)
8    	cout << a << b << endl;
9
10else cout << "ERROR";