File handling in C++

               Files are important feature in any programming language. File handling refers to reading and writing information in the files. Files have some formats like .txt,.csv and so on.

C++ has lot of standard library files to handles file management.

Eg: <fstream> header file  has ofstream, ifstream,fstream.

It also has ifstream(input file stream) and  ofstream(output file stream).

Let us create objects and open the file as follows…

Eg:

‘ifstream’ : ifstream filein("sample.txt");

‘ofstream’ : ofstream fileout("sample.txt");

Where filein ,fileout are objects accordingly.

If you are using ‘fstream’, it needs to open a file like this.

‘fstream fstr("sample.text", mode);’

Here, fstr is the object of fstream. “sample.txt” is the file name. Mode is  the purpose of operation going to be performed in the file. It has variety of types.

Modes:

‘ios::app’ – append the contents to the end of file.

‘ios::ate’ -  The control starts with end of the file.

‘ios::binary’ – it deals with binary data.

‘ios::in’ – it is used to read a file.

‘ios::out’ – it is used to writing.

‘ios::trunc’ – it is used for truncation.

Let us create a C++ program to perform file handling.

C++ Program: To write contents to a file

#include <iostream>

#include <fstream>

using namespace std;

int main() {

   ofstream fi("happy.txt"); // This opens a file for writing

   if (fi.is_open()) {

       fi << "It is a good day to start with:" << endl; // Write the contents to the file

       fi << "This is a test file." << endl;

       fi.close(); // Close the file object

       cout << "The written process is completed" << endl;

   } else {

       cout << "Unable to open the file ." << endl;

   }

   return 0;

}

Output:

The written process is completed

Happy.txt

It is a good day to start with:

This is a test file.

C++ Program: To read the contents in the file

#include <iostream>

#include <fstream>

#include <string>

using namespace std;

int main() {

ifstream fin("happy.txt"); // It Opens a file in read mode

if (fin.is_open()) {

string str;

while (getline(fin, str) ){ // Read the content line by line

cout << str << endl; // Print the contents in the output screen

}

fin.close(); // Close the file

} else {

cout << "Unable to open the file " << endl;

}

return 0;

}

Output:

It is a good day to start with:

This is a test file.

These are the two methods in file handling. Hope, you understood the concept. Try it with other texts. Keep Coding!!!