From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: a07f3367d7,14aa27db81ce3b40
X-Google-Attributes: gida07f3367d7,public,usenet
X-Google-NewGroupId: yes
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news4.google.com!feeder.news-service.com!newsfeed.freenet.de!npeer.de.kpn-eurorings.net!npeer-ng0.de.kpn-eurorings.net!news-2.dfn.de!news.dfn.de!news.uni-weimar.de!not-for-mail
From: stefan-lucks@see-the.signature
Newsgroups: comp.lang.ada
Subject: Re: How to exit an Ada program with (unix shell) error code?
Date: Mon, 4 May 2009 12:07:47 +0200
Organization: Bauhaus-Universitaet Weimar
Message-ID: <Pine.LNX.4.64.0905041147510.22185@medsec1.medien.uni-weimar.de>
References: 
 <49ba30c9-a1e6-4346-8618-d256f87ac301@s31g2000vbp.googlegroups.com>
  <87ws8xkz0y.fsf@willow.rfc1149.net>
 <95866b61-f7e4-482d-8368-8b86528af578@b1g2000vbc.googlegroups.com>
 <10acae13-98dc-48da-9de4-9c01ea07abd4@g19g2000vbi.googlegroups.com>
Reply-To: stefan-lucks@see-the.signature
NNTP-Posting-Host: medsec1.medien.uni-weimar.de
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Trace: tigger.scc.uni-weimar.de 1241439229 21959 141.54.178.228 (4 May 2009
 12:13:49 GMT)
X-Complaints-To: news@tigger.scc.uni-weimar.de
NNTP-Posting-Date: Mon, 4 May 2009 12:13:49 +0000 (UTC)
X-X-Sender: lucks@medsec1.medien.uni-weimar.de
In-Reply-To: 
 <10acae13-98dc-48da-9de4-9c01ea07abd4@g19g2000vbi.googlegroups.com>
Xref: g2news2.google.com comp.lang.ada:5679
Date: 2009-05-04T12:07:47+02:00
List-Id: <comp.lang.ada>

On Mon, 4 May 2009, Ludovic Brenta wrote:

> reinkor wrote on comp.lang.ada:
> > Thanks, but how I terminate the program in a "natural" way
> > (without using goto or "raise exception") ?
> 
> Simply allow the execution to reach the "end;" of the main subprogram.
> 
> with Ada.Command_Line;
> procedure Exit_With_False is
> begin
>    Ada.Command_Line.Set_Exit_Status (1); -- False, in shell terms

     Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Failure);

> end Exit_With_False; -- nothing else required

I believe, it is preferable to use the predefined constants "Success" and 
"Failure" in Ada.Command line:

  1. If you port your program to another (i.e. non-unix) system, 
     it is not clear that "1" maintains the logical value "False". 
     (Perhaps the RM is clear about that -- I didn't check ...) 

  2. Without the comment "-- False, in shell terms", many readers 
     (except for unix-shell experts, of course) would rather expect 

       Ada.Command_Line.Set_Exit_Status (1);

     to indicate a positive result ("True"), rather then "False". 

Here is a slightly larger example:

with Ada.Command_Line;
procedure False_If_No_Arguments is
   package ACL renames Ada.Command_Line;
begin
   if ACL.Argument_Count > 0 then
      ACL.Set_Exit_Status (ACL.Success);
   else
      ACL.Set_Exit_Status (ACL.Failure);
   end if;
end False_If_No_Arguments;

P.S.: (As you see, you can indicate either a positive or a negative 
outcome without ever having to raise an exception ...)



-- 
------ Stefan Lucks   --  Bauhaus-University Weimar  --   Germany  ------
               Stefan dot Lucks at uni minus weimar dot de
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------