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