On Fri, 10 Jul 2009 15:06:29 -0500 Nicolas Williams wrote:
> On Fri, Jul 10, 2009 at 12:36:02PM -0700, Garrett D'Amore wrote:
>> Nicolas Williams wrote:
... ... ...
>
> Also, I'm not sure that apps that read symlinks should have any
> expectations that the contents of a symlink will be a filesystem path.
>
> Nico
The standards place no requirements on what can be stored in a symbolic
link as long as the symlink is never used for pathname resolution.
However, when a symlink is used for pathname resolution, what is
being proposed here does not conform. The standards say the contents
of the symlink replace the filename of the symlink and resolution
continues on the resulting path. (I'm ignoring the exceptions for
resolving access to the symlink itself since they aren't important
to this discussion.)
Given that there is existing practice supporting other behaviors here,
it shouldn't be hard to file an interpretation request to allow alternative
symlink processing, but explicit text for the changes to the definition of
pathname resolution would be required to get a successful interpretation
and have the correct wording appear in the next revision of the standards.
- Don
PS The paragraph in the standard that would have to change to allow
this can be found on P112, L3026-3031 of the 2008 version of the
Single UNIX Specification and the IEEE and ISO POSIX standards
where it currently says:
"In all other cases, the system shall prefix the remaining
pathname, if any, with the contents of the symbolic link
If the combined length exceeds {PATH_MAX}, and the
implementation considers this to be an error, errno shall be
set to [ENAMETOOLONG] and an error indication shall
be returned. Otherwise, the resolved pathname shall be the
resolution of the pathname just created. If the resulting
pathname does not begin with a <slash>, the predecessor
of the first filename of the pathname is taken to be the
directory containing the symbolic link."
This is found in the definition of the General Concept "Pathname
Resolution" in subclause 4.12.
