I do not expect chown, fchownat and lchown to be much used in
UNIX softwares that we care to port.
We stub the functions in libposix so that we can refer them from
standard C libaries (such as newlib).
We will implement them (parsing /cfg/users to determinate uid and gid)
when it will be actually needed from a software ported to Jehanne.
There are a few issues with Plan 9's `access`:
- it has side effects: to test the actual access (that the file
servers can allow or deny according to complex custom rules)
it opens and then closes the file, allocating (and disposing) the fd
- it does not work on directories, since
- they cannot be opened for writing, despite the fact that to
create a file in a directory you must be granted write access on
- they cannot be opened for execution, despite the fact that to
access a file in a directory you must be granted execution access
on that directory
Despite the fact that `access` (even on UNIX) is a violation of the
"tell, don't ask" principle (the access could be forbidden just after
its successful return, making subsequent `open` fail anyway), this
fact smells of a little design error in the file interface.
So, right now we choose to let the libposix's `access` lie on directories:
it will always return 0 on AWRITE and AEXEC for them, accepting that
a successive create/mkdir may fail.
However, a cleaner file API and protocol should allow a simpler `access`
to be implemented for directories too.