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Date: Sun, 24 Feb 2013 10:18:13 +1100
Subject: Re: Python Newbie
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:39721

On Sun, Feb 24, 2013 at 9:52 AM, Michael Torrie <torriem@gmail.com> wrote:
> On 02/23/2013 02:38 PM, Chris Angelico wrote:
>> On Sun, Feb 24, 2013 at 5:29 AM, Dennis Lee Bieber
>> <wlfraed@ix.netcom.com> wrote:
>>>         Error codes under DEC VAX/VMS used odd integers for
>>> "success/information" and even integers for "warning/error" (been too
>>> many years, I think positive integers were success/warning, negative
>>> integers were information/error; I could also be wrong on which set were
>>> even... if 0 were no-info/success then odd were errors and even were
>>> success)).
>>
>> Sounds like IBM DB2 and sqlca.sqlcode - 0 for success, <0 for error,
>>> 0 for warning (or in some cases "status" - an SQLCODE of 100 means
>> "end of result set", which isn't exactly an error but you can't fetch
>> any more from it; it's akin to Python raising StopIteration to
>> terminate a for loop).
>
> All apps that return an error code to the operating system return 0 for
> success, any other value for error.  All command-line utilities work
> this way, all shells, etc.  Even Windows command-line apps work this way
> (errorlevel is what they call it).

Yep, the 0 = success part is pretty much universal (it's been said
that the cause of the downfall of the Roman empire was that, lacking
zero, they were unable to succeed at anything), but the notion of
negative for errors and positive for warnings isn't as clear;
errorlevels and Unix return codes are positive-only.

ChrisA