224 UTL_FILE

Security Model

The set of files and directories that are accessible to the user through UTL_FILE is controlled by a number of factors and database parameters. Foremost of these is the set of directory objects that have been granted to the user. The nature of directory objects is discussed in the Oracle Database SQL Language Reference.

Assuming the user has both READ and WRITE access to the directory object USER_DIR, the user can open a file located in the operating system directory described by USER_DIR, but not in subdirectories or parent directories of this directory.

Lastly, the client (text I/O) and server implementations are subject to operating system file permission checking.

UTL_FILE provides file access both on the client side and on the server side. When run on the server, UTL_FILE provides access to all operating system files that are accessible from the server. On the client side, as in the case for Forms applications, UTL_FILE provides access to operating system files that are accessible from the client.

In the past, accessible directories for the UTL_FILE functions were specified in the initialization file using the UTL_FILE_DIR parameter. However, UTL_FILE_DIR access is no longer recommended. Oracle recommends that you instead use the directory object feature, which replaces UTL_FILE_DIR. Directory objects offer more flexibility and granular control to the UTL_FILE application administrator, can be maintained dynamically (that is, without shutting down the database), and are consistent with other Oracle tools. CREATE ANY DIRECTORY privilege is granted only to SYS and SYSTEM by default.

Note that neither hard nor symbolic links are supported.

On UNIX systems, the owner of a file created by the FOPEN function is the owner of the shadow process running the instance. Normally, this owner is ORACLE. Files created using FOPEN are always writable and readable using the UTL_FILE subprograms. However, non-privileged operating system users who need to read these files outside of PL/SQL may need access from a system administrator.

Operational Notes

The file location and file name parameters are supplied to the FOPEN function as separate strings, so that the file location can be checked against the list of accessible directories as specified by the ALL_DIRECTORIES view of accessible directory objects. Together, the file location and name must represent a legal filename on the system, and the directory must be accessible. A subdirectory of an accessible directory is not necessarily also accessible; it too must be specified using a complete path name matching an ALL_DIRECTORIES object.

UTL_FILE implicitly interprets line terminators on read requests, thereby affecting the number of bytes returned on a GET_LINE call. For example, the len parameter of UTL_FILE.GET_LINE specifies the requested number of bytes of character data. The number of bytes actually returned to the user will be the lesser of:

• The GET_LINE len parameter, or

• The number of bytes until the next line terminator character, or

• The max_linesize parameter specified by UTL_FILE.FOPEN

The FOPEN max_linesize parameter must be a number in the range 1 and 32767. If unspecified, Oracle supplies a default value of 1024. The GET_LINE len parameter must be a number in the range 1 and 32767. If unspecified, Oracle supplies the default value of max_linesize. If max_linesize and len are defined to be different values, then the lesser value takes precedence.

UTL_FILE.GET_RAW ignores line terminators.

UTL_FILE expects that files opened by UTL_FILE.FOPEN in text mode are encoded in the database character set. It expects that files opened by UTL_FILE.FOPEN_NCHAR in text mode are encoded in the UTF8 character set. If an opened file is not encoded in the expected character set, the result of an attempt to read the file is indeterminate. When data encoded in one character set is read and Globalization Support is told (such as by means of NLS_LANG) that it is encoded in another character set, the result is indeterminate. If NLS_LANG is set, it should therefore be the same as the database character set.

Rules and Limits

Operating system-specific parameters, such as C-shell environment variables under UNIX, cannot be used in the file location or file name parameters.

UTL_FILE I/O capabilities are similar to standard operating system stream file I/O (OPEN, GET, PUT, CLOSE) capabilities, but with some limitations. For example, you call the FOPEN function to return a file handle, which you use in subsequent calls to GET_LINE or PUT to perform stream I/O to a file. When file I/O is done, you call FCLOSE to complete any output and free resources associated with the file.

Exceptions

Procedures in UTL_FILE can also raise predefined PL/SQL exceptions such as NO_DATA_FOUND or VALUE_ERROR.

Examples

Example 1

Given the following:

SQL> CREATE DIRECTORY log_dir AS '/appl/gl/log'; 
SQL> GRANT READ ON DIRECTORY log_dir TO DBA; 
SQL> GRANT WRITE ON DIRECTORY log_dir TO DBA; 

SQL> CREATE DIRECTORY USER_DIR AS '/appl/gl/user''; 
SQL> GRANT READ ON DIRECTORY USER_DIR TO PUBLIC; 
SQL> GRANT WRITE ON DIRECTORY USER_DIR TO PUBLIC; 

The following file locations and filenames are valid and accessible as follows:

The following file locations and filenames are invalid:

Example 2

DECLARE 
  V1 VARCHAR2(32767); 
  F1 UTL_FILE.FILE_TYPE; 
BEGIN 
  -- In this example MAX_LINESIZE is less than GET_LINE's length request 
  -- so the number of bytes returned will be 256 or less if a line terminator is seen. 
  F1 := UTL_FILE.FOPEN('USER_DIR','u12345.tmp','R',256); 
  UTL_FILE.GET_LINE(F1,V1,32767); 
  UTL_FILE.FCLOSE(F1); 

  -- In this example, FOPEN's MAX_LINESIZE is NULL and defaults to 1024, 
  -- so the number of bytes returned will be 1024 or less if a line terminator is seen. 
  F1 := UTL_FILE.FOPEN('USER_DIR','u12345.tmp','R'); 
  UTL_FILE.GET_LINE(F1,V1,32767); 
  UTL_FILE.FCLOSE(F1); 

  -- In this example, GET_LINE doesn't specify a number of bytes, so it defaults to 
  -- the same value as FOPEN's MAX_LINESIZE which is NULL in this case and defaults to 1024. 
  -- So the number of bytes returned will be 1024 or less if a line terminator is seen. 
  F1 := UTL_FILE.FOPEN('USER_DIR','u12345.tmp','R'); 
  UTL_FILE.GET_LINE(F1,V1); 
  UTL_FILE.FCLOSE(F1); 
END; 

FILETYPE Record Type

The contents of FILE_TYPE are private to the UTL_FILE package. You should not reference or change components of this record.

TYPE file_type IS RECORD (
   id          BINARY_INTEGER, 
   datatype    BINARY_INTEGER,
   byte_mode   BOOLEAN);

FCLOSE Procedure

This procedure closes an open file identified by a file handle.

UTL_FILE.FCLOSE (
   file IN OUT FILE_TYPE);

WRITE_ERROR
INVALID_FILEHANDLE

FCLOSE_ALL Procedure

This procedure closes all open file handles for the session. This should be used as an emergency cleanup procedure, for example, when a PL/SQL program exits on an exception.

UTL_FILE.FCLOSE_ALL;

WRITE_ERROR

FCOPY Procedure

This procedure copies a contiguous portion of a file to a newly created file. By default, the whole file is copied if the start_line and end_line parameters are omitted. The source file is opened in read mode. The destination file is opened in write mode. A starting and ending line number can optionally be specified to select a portion from the center of the source file for copying.

UTL_FILE.FCOPY (
   src_location    IN VARCHAR2,
   src_filename    IN VARCHAR2,
   dest_location   IN VARCHAR2,
   dest_filename   IN VARCHAR2,
   start_line      IN BINARY_INTEGER DEFAULT 1,
   end_line        IN BINARY_INTEGER DEFAULT NULL);

FFLUSH Procedure

FFLUSH physically writes pending data to the file identified by the file handle. Normally, data being written to a file is buffered. The FFLUSH procedure forces the buffered data to be written to the file. The data must be terminated with a newline character.

Flushing is useful when the file must be read while still open. For example, debugging messages can be flushed to the file so that they can be read immediately.

UTL_FILE.FFLUSH (
   file  IN FILE_TYPE);

FGETATTR Procedure

This procedure reads and returns the attributes of a disk file.

UTL_FILE.FGETATTR(
   location     IN VARCHAR2, 
   filename     IN VARCHAR2, 
   fexists      OUT BOOLEAN, 
   file_length  OUT NUMBER, 
   block_size   OUT BINARY_INTEGER);

FGETPOS Function

This function returns the current relative offset position within a file, in bytes.

UTL_FILE.FGETPOS (
   file IN FILE_TYPE)
 RETURN PLS_INTEGER;

FOPEN Function

This function opens a file. You can specify the maximum line size and have a maximum of 50 files open simultaneously. See also FOPEN_NCHAR Function.

UTL_FILE.FOPEN (
   location     IN VARCHAR2,
   filename     IN VARCHAR2,
   open_mode    IN VARCHAR2,
   max_linesize IN BINARY_INTEGER DEFAULT 1024) 
  RETURN FILE_TYPE;

FOPEN_NCHAR Function

This function opens a file in national character set mode for input or output, with the maximum line size specified. You can have a maximum of 50 files open simultaneously. With this function, you can read or write a text file in Unicode instead of in the database character set.

Even though the contents of an NVARCHAR2 buffer may be AL16UTF16 or UTF8 (depending on the national character set of the database), the contents of the file are always read and written in UTF8. UTL_FILE converts between UTF8 and AL16UTF16 as necessary.

See also FOPEN Function.

UTL_FILE.FOPEN_NCHAR (
   location     IN VARCHAR2,
   filename     IN VARCHAR2,
   open_mode    IN VARCHAR2,
   max_linesize IN BINARY_INTEGER DEFAULT 1024) 
RETURN FILE_TYPE;

FREMOVE Procedure

This procedure deletes a disk file, assuming that you have sufficient privileges.

UTL_FILE.FREMOVE (
   location IN VARCHAR2,
   filename IN VARCHAR2);

FRENAME Procedure

This procedure renames an existing file to a new name, similar to the UNIX mv function.

UTL_FILE.FRENAME (
   src_location     IN   VARCHAR2,
   src_filename     IN   VARCHAR2, 
   dest_location    IN   VARCHAR2,
   dest_filename    IN   VARCHAR2,
   overwrite        IN   BOOLEAN DEFAULT FALSE);

FSEEK Procedure

This procedure adjusts the file pointer forward or backward within the file by the number of bytes specified.

UTL_FILE.FSEEK (
   file             IN OUT  UTL_FILE.FILE_TYPE,
   absolute_offset  IN      PL_INTEGER DEFAULT NULL,
   relative_offset  IN      PLS_INTEGER DEFAULT NULL);

GET_LINE Procedure

This procedure reads text from the open file identified by the file handle and places the text in the output buffer parameter. Text is read up to, but not including, the line terminator, or up to the end of the file, or up to the end of the len parameter. It cannot exceed the max_linesize specified in FOPEN.

UTL_FILE.GET_LINE (
   file        IN  FILE_TYPE,
   buffer      OUT VARCHAR2,
   len         IN  PLS_INTEGER DEFAULT NULL);

GET_LINE_NCHAR Procedure

This procedure reads text from the open file identified by the file handle and places the text in the output buffer parameter. With this function, you can read a text file in Unicode instead of in the database character set.

The file must be opened in national character set mode, and must be encoded in the UTF8 character set. The expected buffer datatype is NVARCHAR2. If a variable of another datatype, such as NCHAR, NCLOB, or VARCHAR2 is specified, PL/SQL will perform standard implicit conversion from NVARCHAR2 after the text is read.

See also GET_LINE Procedure

UTL_FILE.GET_LINE_NCHAR (
   file        IN  FILE_TYPE,
   buffer      OUT NVARCHAR2,
   len         IN  PLS_INTEGER DEFAULT NULL);

GET_RAW Procedure

This procedure reads a RAW string value from a file and adjusts the file pointer ahead by the number of bytes read. UTL_FILE.GET_RAW ignores line terminators.

UTL_FILE.GET_RAW (
   file       IN            UTL_FILE.FILE_TYPE, 
   buffer     OUT NOCOPY    RAW, 
   len        IN            PLS_INTEGER DEFAULT NULL);

PROCEDURE Sys.p (n IN VARCHAR2) IS
      h     UTL_FILE.FILE_TYPE := UTL_FILE.FOPEN('D', n, 'r', 32767);
      Buf   RAW(32767);
      Amnt  CONSTANT PLS_INTEGER := 32767;
    BEGIN
      LOOP
        BEGIN
          Utl_File.Get_Raw(h, Buf, Amnt);
          -- Do something with this chunk
        EXCEPTION WHEN No_Data_Found THEN EXIT; END;
      END LOOP;
      UTL_FILE.FCLOSE (h);
    END;

IS_OPEN Function

This function tests a file handle to see if it identifies an open file. IS_OPEN reports only whether a file handle represents a file that has been opened, but not yet closed. It does not guarantee that there will be no operating system errors when you attempt to use the file handle.

UTL_FILE.IS_OPEN (
   file  IN FILE_TYPE)
  RETURN BOOLEAN;

NEW_LINE Procedure

This procedure writes one or more line terminators to the file identified by the input file handle. This procedure is separate from PUT because the line terminator is a platform-specific character or sequence of characters.

UTL_FILE.NEW_LINE (
   file     IN FILE_TYPE,
   lines    IN BINARY_INTEGER := 1);

PUT Procedure

PUT writes the text string stored in the buffer parameter to the open file identified by the file handle. The file must be open for write operations. No line terminator is appended by PUT; use NEW_LINE to terminate the line or use PUT_LINE to write a complete line with a line terminator. See also "PUT_NCHAR Procedure".

UTL_FILE.PUT (
   file      IN FILE_TYPE,
   buffer    IN VARCHAR2);

PUT_LINE Procedure

This procedure writes the text string stored in the buffer parameter to the open file identified by the file handle. The file must be open for write operations. PUT_LINE terminates the line with the platform-specific line terminator character or characters.

See also "PUT_LINE_NCHAR Procedure".

UTL_FILE.PUT_LINE (
   file      IN FILE_TYPE,
   buffer    IN VARCHAR2,
   autoflush IN BOOLEAN DEFAULT FALSE);

PUT_LINE_NCHAR Procedure

This procedure writes the text string stored in the buffer parameter to the open file identified by the file handle. With this function, you can write a text file in Unicode instead of in the database character set. This procedure is equivalent to the PUT_NCHAR Procedure, except that the line separator is appended to the written text. See also PUT_LINE Procedure.

UTL_FILE.PUT_LINE_NCHAR (
   file    IN FILE_TYPE,
   buffer  IN NVARCHAR2);

PUT_NCHAR Procedure

This procedure writes the text string stored in the buffer parameter to the open file identified by the file handle.

With this function, you can write a text file in Unicode instead of in the database character set. The file must be opened in the national character set mode. The text string will be written in the UTF8 character set. The expected buffer datatype is NVARCHAR2. If a variable of another datatype is specified, PL/SQL will perform implicit conversion to NVARCHAR2 before writing the text.

See also PUT Procedure

UTL_FILE.PUT_NCHAR (
   file      IN FILE_TYPE,
   buffer    IN NVARCHAR2);

PUTF Procedure

This procedure is a formatted PUT procedure. It works like a limited printf(). See also PUTF_NCHAR Procedure.

UTL_FILE.PUTF (
   file    IN FILE_TYPE,
   format  IN VARCHAR2,
   [arg1   IN VARCHAR2  DEFAULT NULL,
   . . .  
   arg5    IN VARCHAR2  DEFAULT NULL]); 

Hello, world!
I come from Zork with greetings for all earthlings.

my_world  varchar2(4) := 'Zork';
...
PUTF(my_handle, 'Hello, world!\nI come from %s with %s.\n',
                my_world,
                'greetings for all earthlings');

PUTF_NCHAR Procedure

This procedure is a formatted version of a PUT_NCHAR Procedure. Using PUTF_NCHAR, you can write a text file in Unicode instead of in the database character set. It accepts a format string with formatting elements \n and %s, and up to five arguments to be substituted for consecutive instances of %s in the format string. The expected datatype of the format string and the arguments is NVARCHAR2.

If variables of another datatype are specified, PL/SQL will perform implicit conversion to NVARCHAR2 before formatting the text. Formatted text is written in the UTF8 character set to the file identified by the file handle. The file must be opened in the national character set mode.

UTL_FILE.PUTF_NCHAR (
   file    IN FILE_TYPE,
   format  IN NVARCHAR2,
   [arg1   IN NVARCHAR2  DEFAULT NULL,
   . . .  
   arg5    IN NVARCHAR2  DEFAULT NULL]); 

PUT_RAW Procedure

This procedure accepts as input a RAW data value and writes the value to the output buffer.

UTL_FILE.PUT_RAW (
   file          IN    UTL_FILE.FILE_TYPE,
   buffer        IN    RAW, 
   autoflush     IN    BOOLEAN DEFAULT FALSE);