Text files

[VelMurugan]

Text files

Text file streams are those where we do not include the ios::binary flag in their opening mode. These files are designed to store text and thus all values that we input or output from/to them can suffer some formatting transformations, which do not necessarily correspond to their literal binary value.

Data output operations on text files are performed in the same way we operated with cout:

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// writing on a text file
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile ("example.txt");
  if (myfile.is_open())
  {
    myfile << "This is a line.\n";
    myfile << "This is another line.\n";
    myfile.close();
  }
  else cout << "Unable to open file";
  return 0;
}


[file example.txt]
This is a line.
This is another line.

Data input from a file can also be performed in the same way that we did with cin:

Code Select Expand

// reading a text file
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main () {
  string line;
  ifstream myfile ("example.txt");
  if (myfile.is_open())
  {
    while (! myfile.eof() )
    {
      getline (myfile,line);
      cout << line << endl;
    }
    myfile.close();
  }

  else cout << "Unable to open file";

  return 0;
}
   

This is a line.
This is another line.

This last example reads a text file and prints out its content on the screen. Notice how we have used a new member function, called eof() that returns true in the case that the end of the file has been reached. We have created a while loop that finishes when indeed myfile.eof() becomes true (i.e., the end of the file has been reached).

Source : cplus