Re^2: "readdir() attempted on invalid dirhandle" error?

[Anonymous Monk]

(OP here) God, I knew it was something stupid and obvious like that! But why on earth would Perl not return an error when opening (not opendiring) a directory? Aargh. Thank you (both) for this. This task doesn't require any fancy tree-walking, the directory will just be a flat folder with files in it, so this is pretty much all I need for this purpose.

[hv]

But why on earth would Perl not return an error when opening (not opendiring) a directory?

As others have shown, there's nothing intrinsically invalid about open on a directory. However I think Perl is definitely capable of giving a more informative error message when you try to use a filehandle in a context that requires a directory handle. I'd recommend opening a github issue tagged as 'Wishlist' suggesting that there's an opportunity for improvement here.

Update: the issue now exists as #22394.

[ikegami]

File handles and directory handles are stored in different slots of the glob. From Perl's perspective, the problem isn't that the provided handle is the wrong kinda of handle; the problem is that the provided glob didn't contain a dir handle.

[ikegami]

Except open and opendir doesn't let you use both slots anymore.

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5.10: Warns when warnings enabled.
5.12: Warns by default.
5.26: "This will be a fatal error in Perl 5.28" to the warning.
5.28: Fatal.