Calling Cobol program from PL/SQL

Question

What is the caling convention for PL/SQL to call a Cobol program?

Answer 1

You cannot do it directly from PL/SQL. PL/SQL is.. well, kind of abstract ito the actual platform it runs on. PL/SQL cannot talk directly to operating system. It cannot (itself) do socket calls, file I/O calls, use the printer, etc.
<p>
All this has to be done using a lower level implementation library - like UTL_FILE for example that wraps internal C written modules that does file I/O. PL/SQL can call these to do I/O on its behalf. Ditto for wrappers like UTL_TCP and others.
<p>
There is no default wrapper for calling external processes from PL/SQL. It can however be done indirectly using the external procedure (EXTPROC) feature, or using Java to do it.
<p>
The latter is the easiest. You create a Java stored proc that can access the operating system and run external programs and commands. You punch a big hole in the Oracle Java security to allow this Java stored proc access to the operating system. Next you create a PL/SQL wrapper for this Java proc which then in turn can be called from PL/SQL.
Just remember that you MUST secure this hole you've punched into Oracle security. If any Oracle user can access this PL/SQL wrapper, they can hack, compromise, trash or simply destroy your entire Oracle account on that server.
Here is the basic code:
create or replace and compile Java Source named "OSCommand" as
-- java:        OS COMMAND
-- descr:       Executes an Operating System Command using the JAVA RTS
-- IN parameter:        os command to execute (including fully qualified path names)
-- OUT parameter:       returncode [\nstring]
--                      where string a max of 32000 chars of the output of the command
--                      (note that \n is used as separators in the string)
--                      returncode=-1   Java RTS error occurred (e.g. command does not exist)
--                      returncode=255  o/s command failed (e.g. invalid command params)
import java.io.*;
import java.lang.*;
public class OSCommand{
        public static String Run(String Command){
                Runtime rt = Runtime.getRuntime();
                int     rc = -1;
                try{
                        Process p = rt.exec( Command );
                        int bufSize = 32000;
                        int len = 0;
                        byte buffer[] = new byte[bufSize];
                        String s = null;
                        BufferedInputStream bis = new BufferedInputStream( p.getInputStream(), bufSize );
                        len = bis.read( buffer, 0, bufSize );
                        rc = p.waitFor();
                        if ( len != -1 ){
                                s = new String( buffer, 0, len );
                                return( s );
                        return( rc+"" );
                catch (Exception e){
                        e.printStackTrace();
                        return(  "-1\ncommand[" + Command + "]\n" + e.getMessage() );
show errors
create or replace function OSexec( cCommand IN string ) return varchar2 is
-- function:    OS EXEC
-- descr:       PL/SQL wrapper for the Java OSCOMMAND stored proc
language        JAVA
name            'OSCommand.Run(java.lang.String) return java.lang.String';
show errors
-- Punching a hole into the Java VM sandbox. The following must be run as
-- sysdba. Substitute SCOTT with the applicable schema that owns the OSEXEC
-- and OSCOMMAND stored procs.
declare
        SCHEMA  varchar2(30) := 'SCOTT';
begin
        dbms_java.grant_permission(
                SCHEMA,
                'SYS:java.io.FilePermission',
                '<<ALL FILES>>',
                'execute'
        dbms_java.grant_permission(
                SCHEMA,
                'SYS:java.lang.RuntimePermission',
                'writeFileDescriptor',
        dbms_java.grant_permission(
                SCHEMA,
                'SYS:java.lang.RuntimePermission',
                'readFileDescriptor',
commit;
end;
-- example: running the Unix/Linux date command to get the current date and time
SQL> select OSexec('/usr/bin/date') as STDOUT from dual;
STDOUT
Fri Sep  1 08:09:34 SAST 2006
1 row selected.
SQL>Edited by: Billy Verreynne on Sep 4, 2008 6:26 PM to make the code snippet readable with the new Jive forum s/w.