diff --git a/Tools/unix/casefn.sh b/Tools/unix/casefn.sh
index 164c9528..28563946 100755
--- a/Tools/unix/casefn.sh
+++ b/Tools/unix/casefn.sh
@@ -1,22 +1,51 @@
 #!/bin/bash
-# given a filename on the command line, echo the form of the file that 
+# given filename on the command line, echo the form of the file that 
 # actually can be opened.  this needs to do filesystem case shenanigans
 #
-n=0
+# we don't handle files with embedded spaces, a horrible idea anyway
+#
+search=/tmp/cn.search.$$
+all=/tmp/cn.all.$$
+in=/tmp/cn.in.$$
+
+function cleanup {
+	rm -f $all $search $in
+}
+
+trap cleanup EXIT
+cleanup
+
+if [ $# -lt 1 ] ; then
+	exit 0
+fi
+
+#
+# normalize to lower case all input file names
+#
+if echo $* | grep -q / ; then
+	echo "no paths allowed"
+	exit 1
+fi
+
 for infn in $* ; do
-	dir=$(dirname $infn)
-	lowname=$(basename $infn | tr '[A-Z]' '[a-z]')
-	cd $dir
-	for i in * ; do
-		cand=$(basename ./"$i" | tr '[A-Z]' '[a-z]')
-		if [ ./"$cand" = ./$lowname ] ; then
-			echo -n "$dir/$i "
-			((n++))
-		fi
-	done
+	echo $infn | tr '[A-Z]' '[a-z]' >> $in
+done
+sort $in > $search
+
+#
+# build join list of file names and lower case forms
+#
+rm -f $in
+for i in * ; do
+	echo $(echo "$i" | tr '[A-Z]' '[a-z]')",$i" >> $in
 done
-if [ $n == 0 ] ; then
-	echo "nofile"
-else
-	echo
+sort $in > $all
+
+join -t, -o 1.2 $all $search | sort -u > $in
+if [ $(wc -l < $in) -gt 0 ] ; then
+	cat $in
+	exit 0
 fi
+
+echo nofile
+exit 2