Re: Host function in SQL/Form 3.0?

In article <38b7bo$f0u_at_debbie.cc.nctu.edu.tw>, <chiu_at_cc.nctu.edu.tw> wrote:
>Hi,
>
> I'm confused about how to make use the HOST function in SQL/FORM 3.0. Is it
>possible I can tell the result executed by HOST. For example, I want to check
>whether some file exists and write:
>
> :system.message_level := 25;
> HOST('ls file', NO_SCREEN);
> IF ERROR_CODE <> 0 THEN
> .......
> END IF;
>
> Why doesn't it work?
>
> Also if I write my own program which returns 0 or -1 to represent success and
>failure and executed by HOST function, is it possible I can tell the result
>according to the value returned by my program. If yes, how can I do?
>
>Thanks for your opinions!
>
>Keny Chiu

The following is a function I wrote to determine if a file name entered in a form exists. It is written for an Unix Operation System.

   DEFINE PROCEDURE

      NAME = file_exists
      DEFINITION = <<<
      /* Procedure:  file_exists
         Type:       Oracle SQL*Forms V3.0
         Author:     Michael A. Rife
         Purpose:    Determine if the passed file exists
         Parameters: A valid file name
         Returns:    Boolean TRUE or FALSE
         Example
         Invocation: If ! file_exists(bogus.file) Then
                       message('File does not exists');
                       bell;
                       raise Form_Trigger_Failure;
                     End If;
         Modifications:
                  Date         By               Description
                  -----------  ---------------- -------------------------------
                  06-APR-1994  Michael A. Rife  Installed
      */
      function file_exists (fn in char)
      return boolean
      is
        return_code boolean;
      begin
        host('[ -r ' || fn || ' ]', NO_SCREEN);
        if form_success then
          return_code := TRUE;
        else
          return_code := FALSE;
        end if;
        return(return_code);
      end;
      >>>