REGEX Option Syntax Issue with Case

[RussCannon]

Hello. My name is Russ, and I am new to this community since I have only recently discovered it. I have been writing Korn Shell scripts since 1990 and am very pleased to find this project.

Since the issue came up in r/ksh about EREs in globbing, I have been experimenting with REGEX in various contexts and have run across a curious behavior in case blocks.

This bit of code:

typeset BOGOSITY='yAdA123YaDa'
case ${BOGOSITY} in
 ~(i)yada~(E)\d{3}yada) printf 'YES\n';;
 *) printf 'NO\n';;
esac

returns the following error in u+ and u+m:

syntax error at line 4: `}yada' unexpected

But, the following prints 'YES':

typeset BOGOSITY='yAdA123YaDa'
case ${BOGOSITY} in
 ''~(i)yada~(E)\d{3}yada) printf 'YES\n';;
 *) printf 'NO\n';;
esac

Why would the first not work, and why would an empty string prefixed to the pattern make it work?

Cheers,
Russ

[McDutchie]

Welcome. :)

I think you found another bug. It makes no sense that these should be different.

[RussCannon]

So, does this need to become an issue?

[McDutchie]

Yes, I've made an issue of it now. See #649

[JohnoKing]

An initial set of testing reveals the syntax error was introduced by the changes made in ksh93t 2008-10-31. Subsequently, this is what the changelog for that version says:

ksh/src/cmd/ksh93/RELEASE

Lines 1225 to 1229 in cfba37d

	08-10-31 --- Release ksh93t ---
	08-10-31 Variable scoping/initialization bugs that could dump core were fixed.
	08-10-24 The lexer now accepts all RE characters for patterns prefixed
	with a ksh ~(...) option expression.
	08-10-24 +For ${var/pat/sub} \0 in sub expands to the text matched by pat.