C++ Files
C++ Files
The fstream library allows us to work with files.
To use the fstream library, include both the standard <iostream> AND the <fstream> header file:
Example
#include <iostream>
#include <fstream>
There are three classes included in the fstream library,
which are used to create, write or read files:
| Class | Description |
|---|---|
ofstream |
Creates and writes to files |
ifstream |
Reads from files |
fstream |
A combination of ofstream and ifstream: creates, reads, and writes to files |
Create and Write To a File
To create a file, use either the ofstream or fstream class,
and specify the name of the file.
To write to the file, use the insertion operator (<<).
Example
#include <iostream>
#include <fstream>
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!";
//
Close the file
MyFile.close();
}
Why do we close the file?
It is considered good practice, and it can clean up unnecessary memory space.
Read a File
To read from a file, use either the ifstream or fstream
class, and the name of the file.
Note that we also use a while loop together with the getline() function
(which belongs to the ifstream class) to read the file line by line, and to print the content of the file:
Example
// Create a
text string, which is used to output the text file
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();
Run example »
Complete <fstream> Reference
For a complete reference of <fstream> classes and functions, go to our C++ fstream Reference.
