Opening and closing files - Mini Project: Build & Apply

Opening and closing files

📖 Scenario: You are creating a simple program to read data from a text file. Before you can read the data, you need to open the file safely and then close it when done.

🎯 Goal: Build a C program that opens a file called data.txt in read mode, checks if the file opened successfully, and then closes the file.

📋 What You'll Learn

Create a FILE* pointer variable named file.

Open the file data.txt in read mode using fopen.

Check if the file opened successfully by testing if file is not NULL.

Close the file using fclose.

Print "File opened and closed successfully." if the file opens, otherwise print "Failed to open file.".

💡 Why This Matters

🌍 Real World

Opening and closing files is a basic task in many programs that need to read or write data, such as reading configuration files or saving user data.

💼 Career

Understanding file handling is essential for software developers, especially those working with system programming, data processing, or embedded systems.

1

Create a FILE* pointer variable

Create a FILE* pointer variable called file and set it to NULL.

C

#include 

int main() {
    // Create a FILE* pointer called file and set it to NULL
    // Your code here

    return 0;
}

Need a hint?

Use FILE *file = NULL; to declare the file pointer.

2

Open the file data.txt in read mode

Use fopen to open the file "data.txt" in read mode "r" and assign it to the variable file.

C

#include 

int main() {
    FILE *file = NULL;
    // Open "data.txt" in read mode and assign to file
    // Your code here

    return 0;
}

Need a hint?

Use file = fopen("data.txt", "r"); to open the file.

3

Check if the file opened successfully

Write an if statement to check if file is not NULL. If it is not NULL, print "File opened and closed successfully.". Otherwise, print "Failed to open file.".

C

#include 

int main() {
    FILE *file = NULL;
    file = fopen("data.txt", "r");

    // Check if file is not NULL
    // Your code here

    return 0;
}

Need a hint?

Use if (file != NULL) to check if the file opened.

4

Close the file

Inside the if block where file is not NULL, close the file using fclose(file);.

C

#include 

int main() {
    FILE *file = NULL;
    file = fopen("data.txt", "r");

    if (file != NULL) {
        // Close the file
        // Your code here
        printf("File opened and closed successfully.\n");
    } else {
        printf("Failed to open file.\n");
    }

    return 0;
}

Need a hint?

Use fclose(file); to close the file inside the if block.