207 UTL_FILE

Using UTL_FILE

• Security Model

• Types

• Operational Notes

• Rules and Limits

• Exceptions

• Examples

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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 [AWAITING XLINK TARGET].

Assuming the user has both READ and WRITE access to the directory object user_dir, the user can open a file located in an accessible directory, but not in subdirectories or parent directories. If a file is a link, the user may be able to open that file as well.

Lastly, the client (text I/O) and server implementations are subject to server-side file system 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 DIRECTORY privilege is granted only to SYS and SYSTEM by default.

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 users who need to read these files outside of PL/SQL may need access from a system administrator.

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Types

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);

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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 and returns the actual number of bytes requested by the GET_RAW len parameter.

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 be the same as the database character set.

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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.

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Exceptions

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

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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 out_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; 

Summary of UTL_FILE Subprograms

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FCLOSE Procedure

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

Syntax

UTL_FILE.FCLOSE (
   file IN OUT FILE_TYPE);

Parameters

Usage Notes

If there is buffered data yet to be written when FCLOSE runs, then you may receive a WRITE_ERROR exception when closing a file.

Exceptions

WRITE_ERROR
INVALID_FILEHANDLE

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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.

Syntax

UTL_FILE.FCLOSE_ALL;

Usage Notes

Exceptions

WRITE_ERROR

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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.

Syntax

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);

Parameters

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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.

Syntax

UTL_FILE.FFLUSH (
   file  IN FILE_TYPE);
invalid_maxlinesize  EXCEPTION;

Parameters

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
WRITE_ERROR

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FGETATTR Procedure

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

Syntax

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

Parameters

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FGETPOS Function

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

Syntax

UTL_FILE.FGETPOS (
   fileid IN file_type)
 RETURN PLS_INTEGER;

Parameters

Return Values

FGETPOS returns the relative offset position for an open file, in bytes. It raises an exception if the file is not open. It returns 0 for the beginning of the file.

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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.

Syntax

UTL_FILE.FOPEN (
   location     IN VARCHAR2,
   filename     IN VARCHAR2,
   open_mode    IN VARCHAR2,
   max_linesize IN BINARY_INTEGER) 
  RETURN file_type;

Parameters

Return Values

FOPEN returns a file handle, which must be passed to all subsequent procedures that operate on that file. The specific contents of the file handle are private to the UTL_FILE package, and individual components should not be referenced or changed by the UTL_FILE user.

Usage Notes

The file location and file name parameters must be supplied to the FOPEN function as quoted 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.

Exceptions

INVALID_PATH: File location or name was invalid.
INVALID_MODE: The open_mode string was invalid.
INVALID_OPERATION: File could not be opened as requested.
INVALID_MAXLINESIZE: Specified max_linesize is too large or too small.

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FOPEN_NCHAR Function

This function opens a file in Unicode 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 charset. See also FOPEN Function.

Syntax

UTL_FILE.FOPEN_NCHAR (
   location     IN VARCHAR2,
   filename     IN VARCHAR2,
   open_mode    IN VARCHAR2,
   max_linesize IN BINARY_INTEGER) 
RETURN file_type;

Parameters

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FREMOVE Procedure

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

Syntax

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

Parameters

Usage Notes

The FREMOVE procedure does not verify privileges before deleting a file. The O/S verifies file and directory permissions. An exception is returned on failure.

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FRENAME Procedure

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

Syntax

UTL_FILE.FRENAME (
   location  IN VARCHAR2,
   filename  IN VARCHAR2, 
   dest_dir  IN VARCHAR2,
   dest_file IN VARCHAR2,
   overwrite IN BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

Permission on both the source and destination directories must be granted. You can use the overwrite parameter to specify whether or not to overwrite a file if one exists in the destination directory. The default is FALSE for no overwrite.

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FSEEK Procedure

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

Syntax

UTL_FILE.FSEEK (
   fid             IN utl_file.file_type,
   absolute_offset IN PL_INTEGER DEFAULT NULL,
   relative_offset IN PLS_INTEGER DEFAULT NULL);

Parameters

Usage Notes

Using FSEEK, you can read previous lines in the file without first closing and reopening the file. You must know the number of bytes by which you want to navigate.

If relative_offset, the procedure seeks forward. If relative_offset > 0, or backward, if relative_offset < 0, the procedure seeks through the file by the number of relative_offset bytes specified.

If the beginning of the file is reached before the number of bytes specified, then the file pointer is placed at the beginning of the file. If the end of the file is reached before the number of bytes specified, then an INVALID_OFFSET error is raised.

If absolute_offset, the procedure seeks to an absolute location specified in bytes.

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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.

Syntax

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

Parameters

Usage Notes

If the line does not fit in the buffer, a VALUE_ERROR exception is raised. If no text was read due to end of file, the NO_DATA_FOUND exception is raised. If the file is opened for byte mode operations, the INVALID_OPERATION exception is raised.

Because the line terminator character is not read into the buffer, reading blank lines returns empty strings.

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN.If unspecified, Oracle supplies a default value of 1024. See also "GET_LINE_NCHAR Procedure".

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
READ_ERROR
NO_DATA_FOUND
VALUE_ERROR

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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 charset. See also GET_LINE Procedure.

Syntax

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

Parameters

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GET_RAW Function

This function 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 and returns the actual number of bytes requested by the GET_RAW len parameter.

Syntax

UTL_FILE.GET_RAW (
   fid  IN  utl_file.file_type, 
   r    OUT NOCOPY RAW, 
   len  IN  PLS_INTEGER DEFAULT NULL);

Parameters

Usage Notes

The subprogram will raise No_Data_Found when it attempts to read past the end of the file. Your application should allow for this by catching the exception in its processing loop.

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;

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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.

Syntax

UTL_FILE.IS_OPEN (
   file  IN FILE_TYPE)
  RETURN BOOLEAN;

Parameters

Return Values

TRUE or FALSE

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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.

Syntax

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

Parameters

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
WRITE_ERROR

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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".

Syntax

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

Parameters

Usage Notes

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
WRITE_ERROR

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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".

Syntax

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

Parameters

Usage Notes

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
WRITE_ERROR

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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 charset. See also "PUT_LINE Procedure".

Syntax

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

Parameters

Usage Notes

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.

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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 charset. See also "PUT Procedure".

Syntax

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

Parameters

Usage Notes

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.

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PUTF Procedure

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

Syntax

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

Parameters

Usage Notes

The format string can contain any text, but the character sequences %s and \n have special meaning.

Examples

The following example writes the lines:

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');

If there are more %s formatters in the format parameter than there are arguments, then an empty string is substituted for each %s for which there is no matching argument.

Exceptions

INVALID_FILEHANDLE
INVALID_OPERATION
WRITE_ERROR

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PUTF_NCHAR Procedure

This procedure is a formatted PUT_NCHAR procedure. Using PUTF_NCHAR, you can write a text file in Unicode instead of in the database charset.

Syntax

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

Parameters

Usage Notes

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.

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PUT_RAW Function

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

Syntax

UTL_FILE.PUT_RAW (
   fid       IN utl_file.file_type,
   r         IN RAW, 
   autoflush IN BOOLEAN DEFAULT FALSE);

Parameters

Usage Notes

You can request an automatic flush of the buffer by setting the third argument to TRUE.

The maximum size of the buffer parameter is 32767 bytes unless you specify a smaller size in FOPEN. If unspecified, Oracle supplies a default value of 1024. The sum of all sequential PUT calls cannot exceed 32767 without intermediate buffer flushes.