How to read a binary file in c? (video, images, or text)

Question

I am trying to copy a file from a specified library to the current directory. I can copy text files perfectly. Any other files become corrupt. The program detects a feof before it should.

#include <stdio.h>

int BUFFER_SIZE = 1024;
FILE *source;
FILE *destination;
int n;
int count = 0;
int written = 0;

int main() {
    unsigned char buffer[BUFFER_SIZE];

    source = fopen("./library/rfc1350.txt", "r");

    if (source) {
        destination = fopen("rfc1350.txt", "w");

        while (!feof(source)) {
            n = fread(buffer, 1, BUFFER_SIZE, source);
            count += n;
            printf("n = %d\n", n);
            fwrite(buffer, 1, n, destination);
        }
        printf("%d bytes read from library.\n", count);
    } else {
        printf("fail\n");
    }

    fclose(source);
    fclose(destination);

    return 0;
}

Answer 1

You need to specify the "b" option to fopen:

source = fopen("./library/rfc1350.txt", "rb");
...
destination = fopen("rfc1350.txt", "wb");

Without it, the file is opened in text ("t") mode, and this results in translation of end-of-line characters.

Answer 2

You need to open the files in binary format rather than text format. In your calls to fopen, use "rb" and "wb" rather than "r" and "w" respectively.

Answer 3

Are you on a Windows machine? Try adding "b" to the mode strings in the calls to fopen.

From man fopen(3):

The mode string can also include the letter 'b' either as a last character or as a character between the characters in any of the two-character strings described above. This is strictly for compatibility with C89 and has no effect; the 'b' is ignored on all POSIX conforming systems, including Linux. (Other systems may treat text files and binary files differently, and adding the 'b' may be a good idea if you do I/O to a binary file and expect that your program may be ported to non-Unix environments.)