Re: [PATCH] errno.3: Add values for all errors

[walter harms <wharms-fPG8STNUNVg@public.gmane.org>]

Am 23.11.2017 21:34, schrieb Michael Kerrisk (man-pages):
> On 11/23/2017 11:57 AM, walter harms wrote:
>>
>>
>> Am 23.11.2017 10:47, schrieb Michael Kerrisk (man-pages):
>>> Hi Walter,
>>>
>>> On 23 November 2017 at 10:23, walter harms <wharms-fPG8STNUNVg@public.gmane.org> wrote:
>>>>
>>>>
>>>> Am 23.11.2017 10:07, schrieb Michael Kerrisk (man-pages):
>>>>> On 11/23/2017 09:31 AM, Christoph Hellwig wrote:
>>>>>> On Wed, Nov 22, 2017 at 07:15:45PM -0500, Wesley Aptekar-Cassels wrote:
>>>>>>> This patch documents the values of error numbers on linux. This is
>>>>>>> something that is in the OpenBSD errno man page, which I find quite
>>>>>>> useful.
>>>>>>
>>>>>> Error numbers are different for different architectures.
>>>>>
>>>>> I was just about to say the same.
>>>>>
>>>>> Someone else recently proposed the same change, and I should have
>>>>> thought then to add the text that I have added just now to errno(3).
>>>>> Hopefully this goes someway to addressing your requirements, Wesley.
>>>>>
>>>>> New text:
>>>>>
>>>>>        On  Linux, the error numbers that correspond to each symbolic name
>>>>>        vary somewhat across architectures.  Therefore, numeric values are
>>>>>        not  included in the list of error names below.  On any particular
>>>>>        system, one can obtain a list of all symbolic error names and  the
>>>>>        corresponding error numbers using the errno(1) command:
>>>>>
>>>> If i read this that would mean the values differ between the linux architectures only.
>>>> I do not ting that was intended.
>>>
>>> Indeed. So, I changed the text to:
>>>
>>>        The  error  numbers  that  correspond  to  each symbolic name vary
>>>        across UNIX systems, and even across  different  architectures  on
>>>        Linux.   Therefore, numeric values are not included in the list of
>>>        error names below.  Portable applications should use the  symbolic
>>>        error  names  (rather than explicit error numbers).  The perror(3)
>>>        and strerror(3) functions can be used to convert  these  names  to
>>>        corresponding textual error messages.
>>>
>>>> What about that:
>>>>
>>>>
>>>> Portability:
>>>>  Programmers should use always the symbolic names as that the value of errno may vary
>>>>  across different systems. Always use strerror (3) (or compareable) to translate
>>>>  the errno code into a human readable string.
>>>>
>>>> note: errno (1) is a nice programm and it could be mentioned but a propper programm
>>>>       simply should not say things like "Error: 13".
>>>
>>> I'm not sure what you are referring to with the preceding line.
>>>
>>
>> I would move the bulk of the text to a portability section or like because this is
>> the section where i would expect that information.
> 
> Moving this off into a separate section doesn't really fit with the
> overall structure of the page, I think. (All changes are pushed to Git
> now, so you can take a look.) So, I'll leave things as they 
> are for now.
> 
>> NTL i was not aware that different linux versions have different code for the same
>> error that should be changed.
>> Also i would drop "Portable" simply write "applications should use ..." there
>> is no reason to write programms that require the numeric value. Corner cases may exists
>> but a man page is no law, so i see no problem.
> 
> So, I think what this convinces me to do is just drop this sentence:
> 
>     Portable applications should use the symbolic error names
>     (rather than explicit error numbers).
> 
> I think you're right that it does not add much to the discussion.
> 
This is not what i had in mind. The sentence is right because we are discussing
the documentation of the real (numeric) values behind symbolic names. The point
is that you write "even across different architectures on Linux" and since i understand
portable == other OS; that means you can *never* use the numeric value. Just imagine
someone will standardize the values across linux only.
Just emphasis that applications should always should use the symbolic error names.

re,
 wh


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