在Oracle运行操作系统命令:2012年Oracle考试:应用技术-百考试题网

　　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.

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>