Copy a file in C

/* filecpy.c */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>


void
get_file_contents(
        FILE *f,
        char **out_buffer,
        long *out_size)
{
        if(!f) {
                assert(!"no file given");
        }

        fseek(f, 0, SEEK_END);
        long len = ftell(f);
        fseek(f, 0, SEEK_SET);

        if(out_size) {
                *out_size = (len + 1);
        }

        if(out_buffer) {
                char *buf = *out_buffer;

                fread(buf, len, 1, f);
                buf[len] = '\0';                
        }
}

int
main() {
        FILE *f = fopen("filecpy.c", "rb");

        if(!f) {
                assert(!"Failed to open file");
                return EXIT_FAILURE;
        }

        long len = 0;
        get_file_contents(f, NULL, &len);

        if(!len) {
                assert(!"File has no size?");
                return EXIT_FAILURE;
        }

        char *buffer = malloc(len);

        if(!buffer) {
                assert(!"Failed to allocate");
                return EXIT_FAILURE;
        }

        get_file_contents(f, &buffer, NULL);

        printf("size: %d\n%s\n", (int)len, buffer);

        return EXIT_SUCCESS;
}

cc filecpy.c && ./a.out