Re: [PATCH] ttyname(3): add NOTES section

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

Hello Christian,

On 04/21/2017 10:05 PM, Christian Brauner wrote:
> Signed-off-by: Christian Brauner <christian.brauner-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>

Thanks! Applied.

Cheers,

Michael


> ---
>  man3/ttyname.3 | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/man3/ttyname.3 b/man3/ttyname.3
> index 0be50c62a..f184b4505 100644
> --- a/man3/ttyname.3
> +++ b/man3/ttyname.3
> @@ -75,7 +75,7 @@ was too small to allow storing the pathname.
>  .\" glibc commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
>  .B ENODEV
>  File descriptor refers to a slave pseudoterminal device
> -but the corresponding pathname could not be found.
> +but the corresponding pathname could not be found (see NOTES).
>  .SH ATTRIBUTES
>  For an explanation of the terms used in this section, see
>  .BR attributes (7).
> @@ -93,6 +93,22 @@ T}	Thread safety	MT-Safe
>  .TE
>  .SH CONFORMING TO
>  POSIX.1-2001, POSIX.1-2008, 4.2BSD.
> +.SH NOTES
> +Processes keeping a file descriptor to a
> +.BR pts (4)
> +device open when switching to
> +.BR mount_namespaces (7)
> +that use a different
> +.IR /dev/ptmx
> +instance may still accidently find that a device path of the same name
> +for that file descriptor exists. However, this device path refers to a
> +different device and thus cannot not be used to modify the device that
> +the file descriptor refers to. Calling
> +.BR ttyname (7)
> +or
> +.BR ttyname_r (7)
> +on the file descriptor in such a mount namespace will cause these
> +functions to return NULL and set errno to ENODEV.
>  .SH SEE ALSO
>  .BR tty (1),
>  .BR fstat (2),
> 


-- 
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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