nsgmls(1) on Linux
The text 941934ed9651, as Debian 2.2 (Potato), Debian 2.1 (Slink), Debian 2.0 (Hamm) shipped it.
a validating SGML parser An SGML System Conforming to International Standard ISO 8879 — Standard Generalized Markup Language
Flags it lists
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-C -
-D -
-a -
-b -
-d -
-data -
-e -
-f -
-g -
-i -
-l -
-m -
-n -
-o -
-p -
-r -
-s -
-t -
-u -
-v -
-w