FILE* output = fopen(output_name, "wb");
FILE* output = fopen(output_name, "rw");
static void copy_range(FILE* input, size_t offset, size_t length,		       const char* output_name){  FILE* output = fopen(output_name, "wb");  EXIT_IF_FALSE(output != NULL);  fseek(input, offset, SEEK_SET);  while (length != 0) {    char buffer[4096];    size_t amount = (length > sizeof(buffer) ? sizeof(buffer) : length);    EXIT_IF_FALSE(fread(buffer, 1, amount, input) == amount);    fwrite(buffer, 1, amount, output);    length -= amount;  }  fclose(output);}