void append_to_file(char *filename, char *line, size_t len)
{
    off_t off;
    int written, closed;
    int fd = open(filename, O_RDWR);
    if (fd == -1) {
        printf("Error opening file: %s\n", filename);
        printf("Error: %s\n", strerror(errno));
        return;
    }
    off = lseek(fd, 0, SEEK_END);
    if (off == -1) {
        printf("Error seeking file: %s\n", filename);
        printf("Error: %s\n", strerror(errno));
        close(fd);
        return;
    }
    written = write(fd, line, len);
    if (written == -1) {
        printf("Error writing to file: %s\n", filename);
        printf("Error: %s\n", strerror(errno));
    }
    closed = close(fd);
    if (closed == -1) {
        printf("Error closing file: %s\n", filename);
        printf("Error: %s\n", strerror(errno));
        return;
    }
}