buf 数据写入文件

 FILE *stream;
    if ((stream = fopen("/root/aaa.pdf", "wb")) == NULL) /* open file TEST.$$$ */
        {
            fprintf(stderr, "Cannot open output file.\n");
            return 1;
        }

        fwrite(dest_buf, dest_size, 1, stream); /* 写的struct文件*/
        fclose(stream); /*关闭文件*/