C++ Files and Streams

In C++ programming we are using the iostream standard library, it provides cin and cout methods for reading from input and writing to output respectively.

To read and write from a file we are using the standard C++ library called fstream. Let us see the data types define in fstream library is.

Data Type	Description
`fstream`	It is used to create files, write information to files, and read information from files.
`ifstream`	It is used to read information from files.
`ofstream`	It is used to create files and write information to the files.

Writing to a file

C++ FileStream example: writing to a file

Example

Let's see the simple example of writing to a text file testout.txt using C++ FileStream programming.

snippet

#include <iostream>
#include <fstream>
using namespace std;
int main () {
  ofstream filestream("testout.txt");
  if (filestream.is_open())
  {
    filestream << "Welcome to RookieNerd.\n";
    filestream << "C++ Tutorial.\n";
    filestream.close();
  }
  else cout <<"File opening is fail.";
  return 0;
}

Output

The content of a text file testout.txt is set with the data: Welcome to RookieNerd. C++ Tutorial.

Reading from a file

C++ FileStream example: reading from a file

Example #1

Let's see the simple example of reading from a text file testout.txt using C++ FileStream programming.

snippet

#include <iostream>
#include <fstream>
using namespace std;
int main () {
  string srg;
  ifstream filestream("testout.txt");
  if (filestream.is_open())
  {
    while ( getline (filestream,srg) )
    {
      cout << srg <<endl;
    }
    filestream.close();
  }
  else {
      cout << "File opening is fail."<<endl; 
    }
  return 0;
}

Note

Before running the code a text file named as "testout.txt" is need to be created and the content of a text file is given below:
Welcome to RookieNerd.
C++ Tutorial.

Output

Welcome to RookieNerd. C++ Tutorial.

C++ Read and Write Example

Example #2

Let's see the simple example of writing the data to a text file testout.txt and then reading the data from the file using C++ FileStream programming.

snippet

#include <fstream>
#include <iostream>
using namespace std;
int main () {
   char input[75];
   ofstream os;
   os.open("testout.txt");
   cout <<"Writing to a text file:" << endl;
   cout << "Please Enter your name: "; 
   cin.getline(input, 100);
   os << input << endl;
   cout << "Please Enter your age: "; 
   cin >> input;
   cin.ignore();
   os << input << endl;
   os.close();
   ifstream is; 
   string line;
   is.open("testout.txt"); 
   cout << "Reading from a text file:" << endl; 
   while (getline (is,line))
   {
   cout << line << endl;
   }	
   is.close();
   return 0;
}

Output

Writing to a text file: Please Enter your name: Nakul Jain Please Enter your age: 22 Reading from a text file: Nakul Jain 22