C File Handling

C file handling

Created By: chatGPT

File handling in C programming allows us to read, write, and manipulate files on disk. This process involves using various file functions defined in the <stdio.h> library. The essential concepts include opening a file, performing operations (like reading or writing), and closing the file once done to free resources. Here’s how you can handle files in C.

// Include the standard I/O library
#include <stdio.h>

int main() {
    FILE *file;
    char data[100];

    // Opening a file in write mode
    file = fopen("example.txt", "w");
    if (file == NULL) {
        printf("Error opening file!\n");
        return 1;
    }

    // Writing to the file
    fprintf(file, "Hello, World!\n");

    // Closing the file
    fclose(file);
    return 0;
}

To read from a file, you can open it in read mode and use functions like fgets() or fscanf(). Always ensure to check whether the file was opened successfully to avoid segmentation faults or unexpected behavior.

// Include the standard I/O library
#include <stdio.h>

int main() {
    FILE *file;
    char buffer[100];

    // Opening a file in read mode
    file = fopen("example.txt", "r");
    if (file == NULL) {
        printf("Error opening file!\n");
        return 1;
    }

    // Reading from the file
    while (fgets(buffer, sizeof(buffer), file)) {
        printf("%s", buffer);
    }

    // Closing the file
    fclose(file);
    return 0;
}

When working with files, you should also be familiar with the different modes you can use when opening a file: r for read, w for write (which creates a new file or truncates an existing one), a for append, and r+ for updating (reading and writing). Understanding these modes will help you manipulate files effectively.

// Include the standard I/O library
#include <stdio.h>

int main() {
    FILE *file;

    // Opening a file in append mode
    file = fopen("example.txt", "a");
    if (file == NULL) {
        printf("Error opening file!\n");
        return 1;
    }

    // Writing additional data to the file
    fprintf(file, "Appending new line.\n");

    // Closing the file
    fclose(file);
    return 0;
}

Error handling is crucial in file operations. Always check if the file pointer is NULL after attempting to open a file. This practice ensures that your program can handle errors gracefully without crashing unexpectedly.

// Include the standard I/O library
#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *file;

    // Attempting to open a nonexistent file
    file = fopen("nonexistent.txt", "r");
    if (file == NULL) {
        perror("Error opening file"); // Print error message
        exit(EXIT_FAILURE); // Exit with failure status
    }

    // Closing the file (this line won't be reached)
    fclose(file);
    return 0;
}