Re: [PATCH] ttyname.3: document ENODEV error code

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Dmitry,

On 03/20/2017 10:58 PM, Dmitry V. Levin wrote:
> Hi,
> 
> On Mon, Mar 20, 2017 at 10:02:15PM +0100, Christian Brauner wrote:
>> Hi,
>>
>> Thanks Dmitry. One comment
>>
>> On 20 Mar 2017 9:51 p.m., "Dmitry V. Levin" <ldv-u2l5PoMzF/Vg9hUCZPvPmw@public.gmane.org> wrote:
>>
>> ---
>>  man3/ttyname.3 | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/man3/ttyname.3 b/man3/ttyname.3
>> index 14c24e7..0be50c6 100644
>> --- a/man3/ttyname.3
>> +++ b/man3/ttyname.3
>> @@ -71,6 +71,11 @@ File descriptor does not refer to a terminal device.
>>  .RB ( ttyname_r ())
>>  .I buflen
>>  was too small to allow storing the pathname.
>> +.TP
>> +.\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
>> +.B ENODEV
>> +File descriptor refers to a slave pseudoterminal device
>> +but the corresponding pathname could not be found.
>>
>> I think it would be good to explicitly mention that ENODEV is set in case
>> the fd does not refer to a pts device in its namespace. Otherwise users
>> might take this as an indication that this is a more generic error which is
>> not the case.
> 
> In fact, this is a more generic error than a namespace mismatch, although
> the latter is the most likely reason.
> 
> Imagine that the corresponding file inside /dev/pts/ is not available for
> some reason and the stat call has failed.  This situation could be
> reproduced e.g. by bind-mounting an empty directory to /dev/pts.
> A subsequent ttyname invocation would end up with ENODEV because the device
> is literally not available although it's withing the same namespace.
> 
> I don't mind if you change the description to mention the namespace case
> as the most likely, but please do not make it the only case when ENODEV
> can happen.

I'm open on this point. If someone wants to write a suitable patch, I'll
probably take it.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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