File Handling

The fstream library allows us to work with files.

To use the fstream library, include both the standard and the header file: 

Example

#include < iostream > 

#include < fstream >

Create and write to a file:

#include<iostream>

#include<fstream>

using namespace std;

int main()

{

    fstream f;

    f.open ( " file.txt " , ios :: out ) ;

    if( !f )

        cout << " error in creating file ";

    else

    {

        cout << " File created ";

        f << " Hi this is OOP ";

        cout << " Data written into file ";

        f.close();

    }

}

Read from a file:

#include 

#include

using namespace std; 

int main() 

{ 

     // Create and open a text file 

     ofstream MyFile("filename.txt"); 

     // Write to the file 

     MyFile << "Files can be tricky, but it is fun enough Hiiiiiii!"; 

     // Close the file 

     MyFile.close(); 

     string myText; 

    // Read from the text file ifstream 

    MyReadFile("filename.txt");

     // Use a while loop together with the getline() function to read the file line by line 

    while ( getline ( MyReadFile ,  myText ) )

    {

            // Output the text from the file 

            cout << myText; 

    } 

    // Close the file 

    MyReadFile.close(); 

}

C++ File Pointers

Every file keeps track of two pointers, which are referred to as get_pointer (in the input mode file) and put_pointer (in the output mode file). These pointers indicate the current position in the file where reading or writing will take place.

In C++, random access is achieved by manipulating the seekg(), seekp(), tellg(), and tellp() functions. The seekg() and tellg() functions allow you to set and examine the get_pointer, and the seekp() and tellp() functions perform these operations on the put_pointer.