cp docbook.cat docbook.cat.orig sed -e '/ISO 8879/d' docbook.cat.orig > docbook.cat cp docbook.cat docbook.cat.orig sed -e '/gml/d' docbook.cat.orig > docbook.cat These commands remove the ENT definitions from the catalog file. cp docbook.cat docbook.cat.orig sed -e 's|DTDDECL "-//OASIS//DTD Docbook V&sgml-dtd-3-version;//EN"|SGMLDECL|g' \ docbook.cat.orig > docbook.cat This command replaces the DTDDECL catalog entry, which is not supported by Linux SGML tools, with the SGMLDECL catalog entry.