File pointers in C - Mini Project: Build & Apply

Working with File Pointers in C

📖 Scenario: You are creating a simple program to write and read text from a file using file pointers in C. This is like writing a note on a piece of paper and then reading it back later.

🎯 Goal: Build a C program that opens a file, writes a message, moves the file pointer to the start, reads the message back, and prints it on the screen.

📋 What You'll Learn

Create a file pointer variable

Open a file named example.txt in write mode

Write the exact string "Hello, File Pointer!" to the file

Use fseek to move the file pointer to the beginning of the file

Read the string back from the file into a character array

Print the read string using printf

Close the file properly

💡 Why This Matters

🌍 Real World

File pointers let programs read and write files, which is useful for saving data, logs, or configuration settings.

💼 Career

Understanding file handling is important for software developers working with data storage, system programming, and application development.

1

Create a file pointer and open a file

Declare a file pointer variable called fp and open a file named example.txt in write mode using fopen.

C

#include 

int main() {
    // Declare file pointer and open file in write mode
    // Your code here
    return 0;
}

Need a hint?

Use FILE *fp to declare the file pointer and fopen("example.txt", "w") to open the file for writing.

2

Write a string to the file

Use fprintf to write the exact string "Hello, File Pointer!" to the file using the file pointer fp.

C

#include 

int main() {
    FILE *fp = fopen("example.txt", "w");
    // Write "Hello, File Pointer!" to the file
    // Your code here
    return 0;
}

Need a hint?

Use fprintf(fp, "Hello, File Pointer!") to write the string to the file.

3

Move file pointer and read the string

Close the file fp, then reopen example.txt in read mode. Use fseek to move the file pointer to the beginning of the file. Read the string into a character array called buffer of size 50 using fgets.

C

#include 

int main() {
    FILE *fp = fopen("example.txt", "w");
    fprintf(fp, "Hello, File Pointer!");
    // Close the file
    // Reopen the file in read mode
    // Move file pointer to start
    // Read string into buffer
    // Your code here
    return 0;
}

Need a hint?

Remember to close the file before reopening it in read mode. Use fseek(fp, 0, SEEK_SET) to move to the start. Use fgets(buffer, 50, fp) to read the string.

4

Print the read string and close the file

Use printf to print the string stored in buffer. Then close the file pointer fp.

C

#include 

int main() {
    FILE *fp = fopen("example.txt", "w");
    fprintf(fp, "Hello, File Pointer!");
    fclose(fp);

    fp = fopen("example.txt", "r");
    fseek(fp, 0, SEEK_SET);

    char buffer[50];
    fgets(buffer, 50, fp);

    // Print the buffer
    // Close the file
    // Your code here
    return 0;
}

Need a hint?

Use printf("%s", buffer) to print the string and fclose(fp) to close the file.