cdesktopenv/NEWS

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This documents significant changes in the 93u+m branch of AT&T ksh93.
For full details, see the git log at:
https://github.com/modernish/ksh
Any uppercase BUG_* names are modernish shell bug IDs.
2020-05-13:
- Fix BUG_CASELIT: an undocumented 'case' pattern matching misbehaviour that
goes back to the original Bourne shell, but wasn't discovered until 2018.
If a pattern doesn't match as a pattern, it was tried again as a literal
string. This broke common validation use cases, e.g.:
n='[0-9]'
case $n in
( [0-9] ) echo "$n is a number" ;;
esac
would output "[0-9] is a number" as the literal string fallback matches the
pattern. As this misbehaviour was never documented anywhere (not for Bourne,
ksh88, or ksh93), and it was never replicated in other shells (not even in
ksh88 clones pdksh and mksh), it is unlikely any scripts rely on it.
Of course, a literal string fallback, should it be needed, is trivial to
implement correctly without this breakage:
case $n in
( [0-9] | "[0-9]") echo "$n is a number or the number pattern" ;;
esac