DBMS_OUTPUT.GET_LINE is a procedure within Oracle’s DBMS_OUTPUT package, which is commonly used for debugging and displaying information in PL/SQL code. This package provides a way for the PL/SQL programs to communicate with the outside world by enabling the display of messages or outputs from PL/SQL blocks, procedures, functions, packages, and triggers. The GET_LINE procedure is specifically used to retrieve a line of information that has been buffered in the DBMS_OUTPUT buffer.
Syntax
The basic syntax of DBMS_OUTPUT.GET_LINE is as follows:
DBMS_OUTPUT.GET_LINE ( line OUT VARCHAR2, status OUT INTEGER );
line: This is an output parameter that will contain the actual line of text retrieved from the DBMS_OUTPUT buffer.
status: This is also an output parameter that indicates the success or failure of the operation. A status of 0 indicates success, meaning a line was successfully retrieved. A status of 1 indicates that there are no more lines to retrieve.
Usage
To use DBMS_OUTPUT.GET_LINE, you must first enable the DBMS_OUTPUT buffer by calling DBMS_OUTPUT.ENABLE, and then you can populate the buffer using the DBMS_OUTPUT.PUT_LINE procedure. After populating the buffer, you can retrieve the buffered lines one at a time using GET_LINE.
Here is an example of how to use DBMS_OUTPUT.GET_LINE:
BEGIN
-- Enable the DBMS_OUTPUT buffer
DBMS_OUTPUT.ENABLE;
-- Put some lines into the buffer
DBMS_OUTPUT.PUT_LINE('Hello, World!');
DBMS_OUTPUT.PUT_LINE('This is a test.');
-- Retrieve and display the lines
LOOP
DECLARE
l_line VARCHAR2(32767);
l_status INTEGER;
BEGIN
DBMS_OUTPUT.GET_LINE(l_line, l_status);
EXIT WHEN l_status != 0; -- Exit the loop if there are no more lines
DBMS_OUTPUT.PUT_LINE(l_line); -- Display the line
END;
END LOOP;
END;
In this example, the DBMS_OUTPUT.PUT_LINE procedure is used to write lines to the buffer, and then DBMS_OUTPUT.GET_LINE is used within a loop to retrieve and display each line until there are no more lines left in the buffer.
Considerations
The DBMS_OUTPUT package is primarily intended for debugging purposes. For production environments or for displaying output to end-users, other methods should be considered.
The buffer size for DBMS_OUTPUT is limited, so for applications that generate a lot of output, it’s important to manage the buffer appropriately to avoid losing messages.
The visibility of DBMS_OUTPUT’s output may depend on the client tool you are using (SQLPlus, SQL Developer, etc.), and some tools require explicit commands to display the buffered output (for example, SET SERVEROUTPUT ON in SQLPlus).