Is there a way to get "EINVAL" style string

Is there a way to get "EINVAL" style string

[Jon Grant]

Hello

I was looking at the man pages looking for a way to get a string of the 
errno value meaning. This is kind of a user question.

This API returns "returns a pointer to a string that describes the error 
code":

http://man7.org/linux/man-pages/man3/strerror.3.html

However, this is a description, e.g. "Invalid argument".  Is there a 
function that would return "EINVAL" or "ENOENT" as the string?

Could I suggest that the text on the man page be updated to clarify what 
would be returned:

"returns a pointer to a string that describes the error code. e.g. 
"Invalid argument" if EINVAL was the errnum."

Best regards, Jon
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Re: Is there a way to get "EINVAL" style string

[Michael Kerrisk (man-pages)]

Hi Jon,

On Sun, Apr 22, 2012 at 11:14 PM, Jon Grant <jg-hus3n9K41k0@public.gmane.org> wrote:
> Hello
>
> I was looking at the man pages looking for a way to get a string of the
> errno value meaning. This is kind of a user question.
>
> This API returns "returns a pointer to a string that describes the error
> code":
>
> http://man7.org/linux/man-pages/man3/strerror.3.html
>
> However, this is a description, e.g. "Invalid argument".  Is there a
> function that would return "EINVAL" or "ENOENT" as the string?

None that I know of. (In passing, I dealt with exactly this problem
for my book with a script that generated the string names; see
http://man7.org/tlpi/code/online/dist/lib/ename.c.inc.html and
http://man7.org/tlpi/code/online/dist/lib/error_functions.c.html)

> Could I suggest that the text on the man page be updated to clarify what
> would be returned:
>
> "returns a pointer to a string that describes the error code. e.g. "Invalid
> argument" if EINVAL was the errnum."

Done for 3.40.

Cheers,

Michael



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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Re: Is there a way to get "EINVAL" style string

[Jon Grant]

Hi Michael

On 22/04/12 22:25, Michael Kerrisk (man-pages) wrote:
> Hi Jon,
>
> On Sun, Apr 22, 2012 at 11:14 PM, Jon Grant<jg-hus3n9K41k0@public.gmane.org>  wrote:
>> Hello
>>
>> I was looking at the man pages looking for a way to get a string of the
>> errno value meaning. This is kind of a user question.
>>
>> This API returns "returns a pointer to a string that describes the error
>> code":
>>
>> http://man7.org/linux/man-pages/man3/strerror.3.html
>>
>> However, this is a description, e.g. "Invalid argument".  Is there a
>> function that would return "EINVAL" or "ENOENT" as the string?
>
> None that I know of. (In passing, I dealt with exactly this problem
> for my book with a script that generated the string names; see
> http://man7.org/tlpi/code/online/dist/lib/ename.c.inc.html and
> http://man7.org/tlpi/code/online/dist/lib/error_functions.c.html)

Interesting. I saw on the ename.c page that the numbers were in the 
table hard coded -- is it guaranteed that 90 will always correspond to 
EPROTOTYPE on a unixy system?

>> Could I suggest that the text on the man page be updated to clarify what
>> would be returned:
>>
>> "returns a pointer to a string that describes the error code. e.g. "Invalid
>> argument" if EINVAL was the errnum."
>
> Done for 3.40.

Great, thank you!
Jon
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Re: Is there a way to get "EINVAL" style string

[Michael Kerrisk (man-pages)]

Hi Jon,

>>> I was looking at the man pages looking for a way to get a string of the
>>> errno value meaning. This is kind of a user question.
>>>
>>> This API returns "returns a pointer to a string that describes the error
>>> code":
>>>
>>> http://man7.org/linux/man-pages/man3/strerror.3.html
>>>
>>> However, this is a description, e.g. "Invalid argument".  Is there a
>>> function that would return "EINVAL" or "ENOENT" as the string?
>>
>>
>> None that I know of. (In passing, I dealt with exactly this problem
>> for my book with a script that generated the string names; see
>> http://man7.org/tlpi/code/online/dist/lib/ename.c.inc.html and
>> http://man7.org/tlpi/code/online/dist/lib/error_functions.c.html)
>
>
> Interesting. I saw on the ename.c page that the numbers were in the table
> hard coded -- is it guaranteed that 90 will always correspond to EPROTOTYPE
> on a unixy system?

No. So, my build code deals with this by using a script to build a
platform-specific ename.c.inc file (have a look at the tarball.)

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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