在Oracle 8i中,往往会出现要在存储过程中运行操作系统命令的情况.一般来说,利用Oracle Enterprise Manager设定作业时可以达到这个目的.但是由于OEM在设定作业缺乏灵活性,设定的作业的参数是固定的.在实际应用当中往往需要在SQL语句当中运行需要随时运行操作系统命令.Oracle 8i没有直接运行OS命令的语句,我们可以利用DBMS_PIPE程序包实现这一要求.

DBMS_PIPE通过创建管道,可以让至少两个进程进行通信.Oracle的管道与操作系统的管道在概念上有相同的地方,但是在实现机制不同.
下面介绍实现具体步骤:

1 创建一个程序包,姑且起名叫DAEMON,SQL语句如下:

/*创建daemon程序包*/
CREATE OR REPLACE PACKAGE BODY daemon AS
/*execute_system是实现运行os命令的函数*/
FUNCTION execute_system(command VARCHAR2,
timeout NUMBER DEFAULT 10)
RETURN NUMBER IS

status NUMBER;
result VARCHAR2(20);
command_code NUMBER;
pipe_name VARCHAR2(30);
BEGIN
pipe_name := DBMS_PIPE.UNIQUE_SESSION_NAME;
DBMS_PIPE.PACK_MESSAGE(''SYSTEM'');
DBMS_PIPE.PACK_MESSAGE(pipe_name);
DBMS_PIPE.PACK_MESSAGE(command);
/*向daemon管道发送表示命令的字符*/
status := DBMS_PIPE.SEND_MESSAGE(''daemon'', timeout);
IF status <> 0 THEN
RAISE_APPLICATION_ERROR(-20010,
''Execute_system: Error while sending. Status = '' status);
END IF;

status := DBMS_PIPE.RECEIVE_MESSAGE(pipe_name, timeout);
IF status <> 0 THEN
RAISE_APPLICATION_ERROR(-20011,
''Execute_system: Error while receiving.
Status = '' status);
END IF;
/*获取返回结果*/
DBMS_PIPE.UNPACK_MESSAGE(result);
IF result <> ''done'' THEN
RAISE_APPLICATION_ERROR(-20012,
''Execute_system: Done not received.'');
END IF;

DBMS_PIPE.UNPACK_MESSAGE(command_code);
DBMS_OUTPUT.PUT_LINE(''System command executed. result = ''
command_code);
RETURN command_code;
END execute_system;
/*stop是让daemon停止*/
PROCEDURE stop(timeout NUMBER DEFAULT 10) IS
status NUMBER;
BEGIN
DBMS_PIPE.PACK_MESSAGE(''STOP'');
status := DBMS_PIPE.SEND_MESSAGE(''daemon'', timeout);
IF status <> 0 THEN
RAISE_APPLICATION_ERROR(-20030,
''stop: error while sending. status = '' status);
END IF;
END stop;
END daemon;


通过Sql*Plus运行以上语句,将为当前用户创建daemon程序包.

2 创建在OS上运行的守护进程,监听由上面的daemon程序包发来的要求执行os命令的语句.以下Pro*C的代码,必须由pro*c先进行预编译.

#include
#include

EXEC SQL INCLUDE SQLCA;

EXEC SQL BEGIN DECLARE SECTION;
char *uid = "scott/tiger";/*在这个地方改为你自己访问的用户,密码,服务名*/
int status;
VARCHAR command[20];
VARCHAR value[2000];
VARCHAR return_name[30];
EXEC SQL END DECLARE SECTION;

void
connect_error()
{
char msg_buffer[512];
int msg_length;
int buffer_size = 512;

EXEC SQL WHENEVER SQLERROR CONTINUE;
sqlglm(msg_buffer, &buffer_size, &msg_length);
printf("Daemon error while connecting:\n");
printf("%.*s\n", msg_length, msg_buffer);
printf("Daemon quitting.\n");
exit(1);
}

void
sql_error()
{
char msg_buffer[512];
int msg_length;
int buffer_size = 512;

EXEC SQL WHENEVER SQLERROR CONTINUE;
sqlglm(msg_buffer, &buffer_size, &msg_length);
printf("Daemon error while executing:\n");
printf("%.*s\n", msg_length, msg_buffer);
printf("Daemon continuing.\n");
}
main()
{
EXEC SQL WHENEVER SQLERROR DO connect_error();
EXEC SQL CONNECT :uid;
printf("Daemon connected.\n");

EXEC SQL WHENEVER SQLERROR DO sql_error();
printf("Daemon waiting...\n");
while (1) {
EXEC SQL EXECUTE
BEGIN
/*接收deamon发来的字符*/
:status := DBMS_PIPE.RECEIVE_MESSAGE(''daemon'');
IF :status = 0 THEN
/*取出字符*/
DBMS_PIPE.UNPACK_MESSAGE(:command);
END IF;
END;
END-EXEC;
IF (status == 0)
{
command.arr[command.len] = ''\0'';
/*如果是stop,该进程就退出*/
IF (!strcmp((char *) command.arr, "STOP"))
{
printf("Daemon exiting.\n");
break;
}

ELSE IF (!strcmp((char *) command.arr, "SYSTEM"))
{
EXEC SQL EXECUTE
BEGIN
DBMS_PIPE.UNPACK_MESSAGE(:return_name);
DBMS_PIPE.UNPACK_MESSAGE(:value);
END;
END-EXEC;
value.arr[value.len] = ''\0'';
printf("Will execute system command ''%s''\n", value.arr);
/*运行os命令*/
status = system(value.arr);
EXEC SQL EXECUTE
BEGIN
DBMS_PIPE.PACK_MESSAGE(''done'');
DBMS_PIPE.PACK_MESSAGE(:status);
:status := DBMS_PIPE.SEND_MESSAGE(:return_name);
END;
END-EXEC;

IF (status)
{
printf
("Daemon error while responding to system command.");
printf(" status: %d\n", status);
}
}
ELSE
{
printf
("Daemon error: invalid command ''%s'' received.\n",
command.arr);
}
}
ELSE
{
printf("Daemon error while waiting for signal.");
printf(" status = %d\n", status);
}
}
EXEC SQL COMMIT WORK RELEASE;
exit(0);
}
以上代码起名为daemon.pc,用proc预编译:

proc iname=daemon.pc userid=用户名/密码@服务名 sqlcheck=semantics

得到daemon.c,在用c进行编译,注意在NT上要把orasql8.lib加上,否则编译通过,连接没法通过.


3 在服务器上运行daemon.exe


4 在sqlplus运行测试语句:
SQL> variable rv number
SQL> execute :rv := DAEMON.EXECUTE_SYSTEM(''ls -la'');
PL/SQL 过程已成功完成。
SQL> execute :rv := DAEMON.EXECUTE_SYSTEM(''dir'');
PL/SQL 过程已成功完成。
SQL>