Using Create directory & UTL_FILE in Oracle

Create directory让我们可以在Oracle数据库中灵活的对文件进行读写操作，极大的提高了Oracle的易用性和可扩展性。
其语法为:
CREATE [OR REPLACE] DIRECTORY directory AS 'pathname';

本案例具体创建如下:

create or replace directory exp_dir as '/tmp';

目录创建以后，就可以把读写权限授予特定用户，具体语法如下:
GRANT READ[,WRITE] ON DIRECTORY directory TO username;

例如:
grant read, write on directory exp_dir to eygle;

此时用户eygle就拥有了对该目录的读写权限。
让我们看一个简单的测试:

SQL> create or replace directory UTL_FILE_DIR as '/opt/oracle/utl_file';
Directory created.

SQL> declare
2 fhandle utl_file.file_type;
3 begin
4 fhandle := utl_file.fopen('UTL_FILE_DIR', 'example.txt', 'w');
5 utl_file.put_line(fhandle , 'eygle test write one');
6 utl_file.put_line(fhandle , 'eygle test write two');
7 utl_file.fclose(fhandle);
8 end;
9 /

PL/SQL procedure successfully completed.

SQL> !
[oracle@jumper 9.2.0]$ more /opt/oracle/utl_file/example.txt
eygle test write one
eygle test write two
[oracle@jumper 9.2.0]$

类似的我们可以通过utl_file来读取文件:

SQL> declare
2 fhandle utl_file.file_type;
3 fp_buffer varchar2(4000);
4 begin
5 fhandle := utl_file.fopen ('UTL_FILE_DIR','example.txt', 'R');
6
7 utl_file.get_line (fhandle , fp_buffer );
8 dbms_output.put_line(fp_buffer );
9 utl_file.get_line (fhandle , fp_buffer );
10 dbms_output.put_line(fp_buffer );
11 utl_file.fclose(fhandle);
12 end;
13 /
eygle test write one
eygle test write two

PL/SQL procedure successfully completed.

可以查询dba_directories查看所有directory.

SQL> select * from dba_directories;

OWNER DIRECTORY_NAME DIRECTORY_PATH
------------------------------ ------------------------------ ------------------------------
SYS UTL_FILE_DIR /opt/oracle/utl_file
SYS BDUMP_DIR /opt/oracle/admin/conner/bdump
SYS EXP_DIR /opt/oracle/utl_file

可以使用drop directory删除这些路径.

SQL> drop directory exp_dir;

Directory dropped

SQL> select * from dba_directories;

OWNER DIRECTORY_NAME DIRECTORY_PATH
------------------------------ ------------------------------ ------------------------------
SYS UTL_FILE_DIR /opt/oracle/utl_file
SYS BDUMP_DIR /opt/oracle/admin/conner/bdump