Re: glob qualifier '-' doesn't work correctly on dangling symlinks

[Stephane Chazelas <stephane@chazelas.org>]

2020-04-13 01:38:45 +0200, Vincent Lefevre:
[...]
> > Well, as seen in the varying interpretations made by the various
> > implementations, it is not that clear. How do you determine
> > whether a file exists or not? What does "exist" mean?
> 
> You necessarily know it, or that's an error case (permission denied
> or whatever). The behavior may not be clear in case of error, but
> one can expect at least a non-zero exit status:
[...]

Are you saying that EACCES is an "error" but ENOENT is not? How
about ENOTDIR, ELOOP? None of /etc/passwd/foo, /etc/pesswd/foo,
symloop/foo or /root/foo exist on my system, a stat() on a
symlink to those would return ENOTDIR, ENOENT, ELOOP, EACCES. On
which one should find -L return with a non-zero exit status?
Which one(s) should find -L . -type l (or find . -xtype l)
print?

[...]
>   -e  pathname
>     True if pathname resolves to an existing directory entry.
>     False if pathname cannot be resolved.
> 
> BTW, I don't know how zsh behaves on "[[ -e pathname ]]" in case of
> error other than ENOENT in the pathname resolution, but this should
> be documented (and ditto for the other conditional expressions).
[...]

The mention of "directory entry" is misleading here. It's really
about a "file" more than a "directory entry" as stat() gets you
to the inode.

Maybe:

 -e  pathname
   True if pathname can be determined to resolve to an existing
   file (of any type). False otherwise. Note that since this
   applies after symlink resolution, that will return false for
   existing but broken symlinks. Use [[ -e /path/to/file || -L
   /path/to/file ]] to account for that (requires search access
   to the directory).

But that's probably going to confuse the reader more than help
them.

To confuse them even more, we could also mention
(){(($#))} (#I)/path/to/file(|)(N) to really check for file
being an entry in /path/to (requires read access to the
directory and extendedglob for (#I) used to cancel nocaseglob
in case it's enabled).

IIRC the "test" operator was initially "-a" (for "accessible"?)
for that which was a bit more accurrate (or maybe it was a
SYSV-sh vs ksh thing, I can't remember).

See also
https://stackoverflow.com/questions/638975/how-do-i-tell-if-a-regular-file-does-not-exist-in-bash/40046642#40046642

-- 
Stephane