cat $PKG/install/slack-desc | grep "^${PRGNAM}" > \
$OUTPUT/$PRGNAM-${VERSION}-${ARCH}-${BUILD}${TAG}.txt


alien's, (usually)
and now Slackware's, generally:
################################

cat $PKG/install/slack-desc | grep "^${PKGNAM}" > $TMP/$PKGNAM-${VERSION}-${ARCH}-${BUILD}.txt