Using UTL_FILE to find files on the OS

Here is how to use UTL_FILE to detect a file on the OS insead of writing a UNIX or DOS script. The procedure can be scheduled through DBA_JOBS to check for the existence of a file that has been FTP'ed, for example. Once the file has been detected, it calls another procedure to start processing. 

  
REM check_for_file.sql
REM   Steve Montgomerie
REM   26 April 2000
REM
REM Use UTL_FILE to detect the presence of an OS file
REM like when looking for a file to arrive from 
REM an FTP process. Once the file is detected call
REM another procedure to start processing.
REM
REM If the file is detected call another procedure
REM to start processing or else simply exit the routine.
REM
REM Typically in the case of FTP two files are sent. The
REM dump file and a dummy file. Check for the dummy file
REM so as not to process a dump that has not been completly
REM transferred.
REM
REM Schedule this procedure through DBMS_JOBS
REM To not process more than once create a small table
REM and set a flag that this procedure can check.
REM Alternatively use a JAVA stored procedure to delete
REM dummy file when it is detected. 
CREATE OR REPLACE PROCEDURE check_for_file 
AS
file_chk_file    UTL_FILE.FILE_TYPE;
BEGIN 
file_chk_file := UTL_FILE.FOPEN ('c:temp', 'dummy.txt', 'R');   
-- start_job; Call a procedure to start processing here
UTL_FILE.FCLOSE_ALL;
     EXCEPTION
       WHEN UTL_FILE.INVALID_OPERATION then
         RAISE_APPLICATION_ERROR(-20102,'Invalid Operation');
END;
/

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This was first published in August 2002

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