c++ - MySQL触发器错误＃2013-查询期间与MySQL服务器的连接断开

Question

我想创建一个MySQL触发器，当将一行插入MySQL表时，在其中执行C++程序。为此，我使用的是LIB_MYSQLUDF_SYS，它已成功安装为UDF。我的代码基于this教程。

这是我的触发代码:

DELIMITER @@
CREATE TRIGGER startSimulator 
BEFORE INSERT ON `trigger`
FOR EACH ROW 
BEGIN
 DECLARE cmd CHAR(255);
 DECLARE result int(10);
 SET cmd=CONCAT('/home/lab/Dropbox/simulator/version_unified/./simulator');
 SET result = sys_exec(cmd);
END;
@@
DELIMITER ;

如果不清楚，则使用./simulator执行系统程序。但是，当我使用INSERT INTO trigger (trigger) VALUES (yes)将行插入到“触发器”表中时，出现以下错误:
#2013 - Lost connection to MySQL server during query
当我删除触发器时，查询执行正常。有谁知道为什么会这样吗？
mysqld --log-warnings=2产生:

130719 15:53:59 [Note] Plugin 'FEDERATED' is disabled.
mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
130719 15:53:59 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
130719 15:53:59 InnoDB: The InnoDB memory heap is disabled
130719 15:53:59 InnoDB: Mutexes and rw_locks use GCC atomic builtins
130719 15:53:59 InnoDB: Compressed tables use zlib 1.2.3.4
130719 15:53:59 InnoDB: Initializing buffer pool, size = 128.0M
130719 15:53:59 InnoDB: Completed initialization of buffer pool
130719 15:53:59  InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.

Answer 1

更改

SET cmd=CONCAT('/home/lab/Dropbox/simulator/version_unified/./simulator');

至

SET cmd=CONCAT('/home/lab/Dropbox/simulator/version_unified/simulator');

当文件位于当前工作目录中时，将使用./。