Re: strange glob parsing

[dana <dana@xxxxxxx>]

On Mon 2 Jun 2025, at 22:19, Lawrence Velázquez wrote:
> It's not what I expect.  I believe that POSIX requires the synonymous
> "[!]" to match a literal '[' followed by a literal '!' followed by
> a literal ']', and bash, dash, and ksh perform matching this way.

i agree that it's unexpected but not sure about the rest? posix isn't
very explicit but it implies (in 9.3.5) that the body of the bracket
expression (the ... in [...] or [^...]) can't be empty. all the regex
engines i tested treat both [] and [^] as erroneous so that seems to be
the case

linux glob(7) is clearer:

> The string enclosed by the brackets cannot be empty

and the context implies that that extends to [!...]

afaict bash treats both [] and [^] as never-matching, which is in
accordance with that

On Mon 2 Jun 2025, at 22:19, Lawrence Velázquez wrote:
> These are expected.  In each of "[]...]", "[!]...]", and "[^]...]",
> the leading ']' represents itself in the list of candidate characters
> and doesn't preemptively terminate the bracket expression.

also agreed that this case is behaving as expected, consistently with
posix and with other implementations

the [^] case is the one that's arguably unexpected. that's due to
workers/35131. i'm not sure whether that specific behaviour with '^' was
intended or not. i suppose if [] matches nothing it makes a certain
sense for [^] to match everything, but as mentioned bash works in a
different way which is also logical and more consistent with regex

dana