On 03/08/2025 05:33, Collin Funk wrote:
Hi Eric,
You said:
Among other things, I can see the following changes that coreutils
will need to make to become compliant, or else we need to push back on
the POSIX folks if we have strong reasons to complain that their
specification will break things:
POSIX wants 'readlink non-symlink' to output a diagnostic; that is, it
looks like POSIX wants us to behave like '-v' is enabled by default
(our current behavior of -q by default will be non-compliant).
I have attached a patch that I think is correct for readlink.
It is a bit more complex than just behaving the same as 'readlink -v'
previously would. This is because the behavior of non-POSIX
options. Here are some commands:
$ touch file
$ ln -s symlink file
# Example 1
$ readlink -v file
readlink: file: Invalid argument
# Example 2
$ readlink -v -f file
/home/collin/file
If 'readlink -v' where 'POSIXLY_CORRECT=1 readlink' then example 1 would
conform. I think that example 2 would violate POSIX.
So, when POSIXLY_CORRECT is enabled we can call 'readlink', check for
errors, and then canonicalize if it is successful.
I'd say any option apart from -n implicitly disables strict POSIX conformance,
since those options are not in POSIX at all. So all I'd do is enable -v
if POSIXLY_CORRECT is set. There is the argument for defaulting to -v,
but I see FreeBSD does not output an error either if file is not a symlink,
so it's probably best to only enable -v if POSIXLY_CORRECT is set.
In NEWS this should be under "Changes in behavior" rather than "New Features".
Thanks for following up on this.
Padraig.
