米ハーバード大学 CS50：課題「メモリカードに保存された画像ファイルを復元する方法」の回答例（Harvard CS50 Week 4: Problem Set 4 − Recover） 

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

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        printf("Usage: ./recover card.raw");
        return 1;
    }
    // Open file for reading
    FILE *input_file = fopen(argv[1], "r");

    // Input_file pointer fail to open then REturn error code "Could not open file"
    if (input_file == NULL)
    {
        printf("Could not open file");
        return 2;
    }

    // Declare a variable to unsigned char to store 512 chunks array
    unsigned char buffer[512];

    // For the purpose of counting of image later in the loop
    int count_image = 0;

    // An uninitialize file pointer to use to output data gotten from input file
    FILE *output_file = NULL;

    // Allocating memory to filename
    char *filename = malloc(8 * sizeof(char));

    // Read 512 bytes from input_file and store on the buffer
    while (fread(buffer, sizeof(char), 512, input_file))
    {
        // Check if bytes is start of a JPEG
        if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
        {
            // Write jpeg into file name in form 001.jpg, 002.jpg and so on
            sprintf(filename, "%03i.jpg", count_image);

            // Open Out_file for writing
            output_file = fopen(filename, "w");

            // Count number of image found
            count_image++;
        }

        // Check if output have been used for valid input
        if (output_file != NULL)
        {
            fwrite(buffer, sizeof(char), 512, output_file);
        }

    }

    free(filename);
    fclose(output_file);
    fclose(input_file);

    return 0;
}