#include <iostream>
#include <fstream>
using namespace std;
int main() {
// Write to a file
ofstream outfile(“myfile.txt”); // Create an output file stream
if (outfile.is_open()) {
outfile << “Hello, world!\n”;
outfile << “This is some text written to a file.\n”;
outfile.close(); // Close the file stream
cout << “Data written to file successfully.” << endl;
} else {
cout << “Error opening file for writing.” << endl;
}
// Read from the file
ifstream infile(“myfile.txt”); // Create an input file stream
if (infile.is_open()) {
string line;
while (getline(infile, line)) {
cout << line << endl;
}
infile.close(); // Close the file stream
} else {
cout << “Error opening file for reading.” << endl;
}
return 0;
}
Output:
Data written to file successfully.
Hello, world!
This is some text written to a file.
Here’s a step-by-step explanation of the code:
1. Headers and Namespace:
- #include <iostream>: Includes the iostream header for input/output operations.
- #include <fstream>: Includes the fstream header for file input/output operations.
- using namespace std;: Brings the std namespace into scope for convenient use of elements like cout, cin, ofstream, ifstream, etc.
2. Writing to a File:
- ofstream outfile(“myfile.txt”);: Creates an output file stream object named outfile and associates it with the file “myfile.txt”.
- if (outfile.is_open()) { … }: Checks if the file was opened successfully.
- outfile << “Hello, world!\n”;: Writes the string “Hello, world!” to the file, followed by a newline character.
- outfile << “This is some text written to a file.\n”;: Writes another string to the file.
- outfile.close();: Closes the file stream to ensure data is written and resources are released.
3. Reading from the File:
- ifstream infile(“myfile.txt”);: Creates an input file stream object named infile to read from “myfile.txt”.
- if (infile.is_open()) { … }: Checks if the file was opened successfully for reading.
- string line;: Declares a string variable to store lines read from the file.
- while (getline(infile, line)) { … }: Reads lines from the file using getline() until the end of the file is reached.
- cout << line << endl;: Prints each line to the console.
- infile.close();: Closes the file stream when reading is finished.
4. Key Points:
- File Streams: The fstream library provides file stream objects for input (ifstream) and output (ofstream) operations.
- Opening and Closing Files: Use the open() function to create a file stream and associate it with a file, and use close() to release resources.
- Error Handling: Always check if files were opened successfully using is_open() to handle potential errors.
- Writing to Files: Use the insertion operator (<<) to write data to a file stream.
- Reading from Files: Use the getline() function to read lines from a file stream.
