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. |
C++ FileStream example: writing to a file
Let's see the simple example of writing to a text file testout.txt using C++ FileStream programming.
Example
Example
#include <iostream>
#include <fstream>
using namespace std;
int main () {
ofstream filestream("testout.txt");
if (filestream.is_open())
{
filestream << "Welcome to javaCppTutorial.\n";
filestream << "C++ Tutorial.\n";
filestream.close();
}
else cout <<"File opening is fail.";
return 0;
}
Output:
Output
The content of a text filetestout.txtis set with the data:
Welcome to javaCppTutorial.
C++ Tutorial.
C++ FileStream example: reading from a file
Let's see the simple example of reading from a text file testout.txt using C++ FileStream programming.
Example
Example
#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 javaCppTutorial. C++ Tutorial.
Output:
Output
Welcome to javaCppTutorial.
C++ Tutorial.
C++ Read and Write Example
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.
Example
Example
#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:
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