More about the FILELIST program

The normal way of executing this program is as follows (STACK_ERR because I'm using the -R flag)

SELECT SQL.TMPFILE INTO :ST6 FROM DUMMY;
:CHKDIR = SYSPATH ('LOAD', 0);
EXECUTE FILELIST :CHKDIR, :ST6, '-R', '-d', SQL.TMPFILE;
LINK STACK_ERR TO :ST6;
SELECT * FROM STACK_ERR FORMAT; /* this is in Windbi */

If one omits the final parameter (SQL.TMPFILE), then the following is displayed

the option '-msg_file' is required but missing
Positional arguments:
  --dirname arg           directory name
  --linked_stack_file arg link to STACK6 or STACK_ERR for results
  --msg_file arg          text file for return messages

General arguments:
  --u                 names lowercased (result in STACK6 by default)
  --l                 names uppercased (result in STACK6 by default)
  --f                 forces resuts to be written to STACK_ERR
  --R                 performes subdirectories scan (result in STACK_ERR)
  --d                 put directory names in result
  --A 

The option '-msg_file' presumably refers to SQL.TMPFILE that I omitted from the procedure call. I have no idea where else this technique of omitting 'the text file for return messages' can be used in order to get a program's help. COPYFILE and MOVEFILE don't have such a parameter, although they do allow an optional STACK parameter that can be checked for program success or failure.