文件读写问题

今天写一个程序的时候发现文件的读写会发生相互的影响，当交错地进行文件的读写的时候会发生意料不到的错误。
int main(void)
{
char buffer[256];
MYSQL * mysql = mysql_init(0);
mysql_real_connect(mysql, “localhost”, “root”, “root”, “webrobot”, 0, 0, 0);
mysql_query(mysql, “insert into robot values(‘pabababab’,654235)”);
FILE * file = fopen(“3.txt”, “r+”);
fputs(“wocao45564”, file);
fgets(buffer, sizeof(buffer), file);
fclose(file);
return 0;
}

文件打开后显示：
ao45564屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯屯?
具体原因有待解决。