In-depth analysis of C language file operation problems

In-depth analysis of C language file operation problems

Preface

File operation is an important function in C language programming. However, it can also be a challenging area, especially when dealing with complex file structures. This article will deeply analyze common problems in C language file operation and provide practical cases to clarify solutions.

Open and close files

When opening a file, there are two main modes: r (read-only) and w (write-only). To open a file, you can use the fopen() function:

 FILE *fp = fopen("file.txt", "r");

After opening the file, it must be closed after use to free the resource:

 fclose(fp);

Read and write data

You can use fgets() and fscanf() functions to read data from a file:

 char buffer[100];
fgets(buffer, 100, fp); // Read up to 100 characters from the file int num;
fscanf(fp, "%d", &num); // Read an integer from the file

You can use fprintf() and fputs() functions to write data to a file:

 fprintf(fp, "Hello, world!\n"); // Write a string to the file fputs("Goodbye, world!", fp); // Write a string to the file

Process text files

A text file is a simple file type that stores text data. In C language, you can use the fgetc() , fputc() , fgets() , and fputs() functions to process text files.

Process binary files

A binary file is a file type that stores non-text data, such as an image or audio file. In C language, fread() and fwrite() functions can be used to process binary files.

Practical case: Reading and writing binary image files

The following is a practical case of reading and writing binary image files:

 #include <stdio.h>
#include <stdlib.h>

// Read image file void read_image(char *filename) {
    FILE *fp = fopen(filename, "rb");
    if (fp == NULL) {
        perror("fopen");
        exit(1);
    }

    // Get the image size unsigned int width, height;
    fread(&width, sizeof(unsigned int), 1, fp);
    fread(&height, sizeof(unsigned int), 1, fp);

    // Allocate memory and read pixel data unsigned char *pixels = malloc(width * height * sizeof(unsigned char));
    fread(pixels, sizeof(unsigned char), width * height, fp);

    // Close the file fclose(fp);
}

// Write to the image file void write_image(char *filename) {
    FILE *fp = fopen(filename, "wb");
    if (fp == NULL) {
        perror("fopen");
        exit(1);
    }

    // Get the image size unsigned int width, height;
    printf("Enter image width: ");
    scanf("%u", &width);
    printf("Enter image height: ");
    scanf("%u", &height);

    // Allocate memory and get pixel data unsigned char *pixels = malloc(width * height * sizeof(unsigned char));
    printf("Enter pixel values ​​(0-255): ");
    for (int i = 0; i < width * height; i ) {
        scanf("%hhu", &pixels[i]);
    }

    // Write image size fwrite(&width, sizeof(unsigned int), 1, fp);
    fwrite(&height, sizeof(unsigned int), 1, fp);

    // Write pixel data fwrite(pixels, sizeof(unsigned char), width * height, fp);

    // Close the file fclose(fp);
}

int main() {
    // Read the image file read_image("image.bin");

    // Write to the image file write_image("new_image.bin");

    return 0;
}

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