UTL_FILE package allows you to read and write HDFS files:

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'w');
  UTL_FILE.PUT_LINE(f, 'Hello, world!');
  UTL_FILE.FCLOSE(f);
END;

In this example we create /user/dm/hello.txt in HDFS, write a single line and close the file.

Before you can work with a file using UTL_FILE package you have to declare a variable of UTL_FILE.FILE_TYPE. You assign a value to this variable using UTL_FILE.FOPEN function and then use it in all other functions as an argument.

Declaring UTL_FILE.FILE_TYPE variables:

DECLARE
  f UTL_FILE.FILE_TYPE;
  f2 UTL_FILE.FILE_TYPE;

FOPEN function opens a file.

Syntax:

file_handle: = FOPEN(directory, file, mode);

Parameters:

File Open Modes:

• 'r' - Open file for reading.
• 'w' - Open file for writing. If the file does not exist it is created. If the file already exists its content is overwritten.

Return Value:

FOPEN returns UTL_FILE.FILE_TYPE file handle that you have to pass to all other functions operating on the file.

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'w');
END;

GET_LINE function reads a text string from an open file. The function reads until a new line (not included to the output string), end of file or the specified maximum length.

Syntax:

UTL_FILE.GET_LINE(file_handle, var [, len]);

Parameters:

Return Value:

No.

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
  s VARCHAR(100);
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'r');
  UTL_FILE.GET_LINE(f, s, 100);
END;

PUT_LINE function writes a text string to the file. The function appends a line terminator.

Syntax:

UTL_FILE.PUT_LINE(file_handle, text);

Parameters:

Return Value:

No.

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'w');
  UTL_FILE.PUT_LINE(f, 'Hello, world!');
END;

PUT_LINE function writes a text string to the file. Unlike PUT_LINE this function does not append a line terminator.

Syntax:

UTL_FILE.PUT(file_handle, text);

Parameters:

Return Value:

No.

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'w');
  UTL_FILE.PUT(f, 'Hello, world!');
END;

FCLOSE function closes an open file identified by a file handle.

Syntax:

UTL_FILE.FCLOSE(file_handle);

Parameters:

Return Value:

No.

Example:

DECLARE
  f UTL_FILE.FILE_TYPE;
BEGIN
  f := UTL_FILE.FOPEN('/user/dm', 'hello.txt', 'w');
  UTL_FILE.FCLOSE(f);
END;