diff --git a/2015/howe/prog-test.sh b/2015/howe/prog-test.sh
index d5411829e..55a8293cd 100755
--- a/2015/howe/prog-test.sh
+++ b/2015/howe/prog-test.sh
@@ -3,13 +3,14 @@
 
 PROG="./prog"
 
-args=$(getopt 'f:w' $*)
-if [ $? -ne 0 ]; then
+args=$(getopt 'f:w' "$@")
+status="$?"
+if [[ $status -ne 0 ]]; then
 	echo "usage: prog-test.sh [-w][-f flags]"
 	exit 2
 fi
-set -- $args
-while [ $# -gt 0 ]; do
+set -- "$args"
+while [[ $# -gt 0 ]]; do
 	case "$1" in
 	-w)
 		PROG="./prog-w64"
@@ -20,6 +21,8 @@ while [ $# -gt 0 ]; do
 	--)
 		shift; break
 		;;
+	*)
+		;;
 	esac
 	shift
 done
@@ -30,17 +33,18 @@ function distance
 	typeset B="$1"; shift
 	typeset expect="$1"; shift
 
-	printf "$A" | sed -e 's/./&\
-/g' >$A.tmp
-	printf "$B" | sed -e 's/./&\
-/g' >$B.tmp
+	printf "%s" "$A" | sed -e 's/./&\
+/g' >"$A.tmp"
+	printf "%s" "$B" | sed -e 's/./&\
+/g' >"$B.tmp"
 
-	echo "<<< A='$A' B='$B' $@"
-	typeset dist=$($PROG -d $@ $A.tmp $B.tmp | tr -d '\r')
+	echo "<<< A='$A' B='$B' $*"
+	typeset dist
+	dist=$("$PROG" -d "$@" "$A.tmp" "$B.tmp" | tr -d '\r')
 
 	printf '>>> got=%d expect=%d ' "$dist" "$expect"
 
-	if [ "$dist" -ne "$expect" ]; then
+	if [[ "$dist" -ne "$expect" ]]; then
 		echo FAIL
 		return 1
 	fi
@@ -56,12 +60,12 @@ function dif
 	typeset expect="$1"; shift
 
 	echo "==== $A $B"
-	$PROG $A $B | tee patch.tmp
+	"$PROG" "$A" "$B" | tee patch.tmp
 	typeset ex=$?
 
-	if [ "$expect" -eq 0 ]; then
-		printf "got=%d expect=%d " $ex $expect
-		if [ $expect -ne $ex ]; then
+	if [[ "$expect" -eq 0 ]]; then
+		printf "got=%d expect=%d " "$ex" "$expect"
+		if [[ $expect -ne $ex ]]; then
 			echo FAIL
 			return 1
 		fi
@@ -70,7 +74,7 @@ function dif
 	fi
 
 	printf "forward patch "
-	cp $A copy.tmp
+	cp "$A" copy.tmp
 	if ! patch -f -s copy.tmp patch.tmp ; then
 		echo FAIL
 		return 1
@@ -78,7 +82,7 @@ function dif
 	echo -OK-
 
 	printf "forward compare "
-	if ! cmp $B copy.tmp ; then
+	if ! cmp "$B" copy.tmp ; then
 		echo FAIL
 		return 1
 	fi
@@ -92,7 +96,7 @@ function dif
 	echo -OK-
 
 	printf "reverse compare "
-	if ! cmp $A copy.tmp ; then
+	if ! cmp "$A" copy.tmp ; then
 		echo FAIL
 		return 1
 	fi
@@ -101,17 +105,17 @@ function dif
 	return 0
 }
 
-distance "1" "1" 0 $flags
-distance "1" "A" 2 $flags
-distance "123" "ABCDE" 8 $flags
-distance "ABCDE" "123" 8 $flags
-distance "ABD" "ABCD" 1 $flags
-distance "ABCD" "ABD" 1 $flags
-distance "ABCD" "ACDBECFD" 4 $flags
-distance "ABCDEF" "ABXYEFCD" 6 $flags
-distance "ABCDEFGHIJK" "ABCEFGIJKDEFGHIJK" 6 $flags
-distance "ABCABBA" "CBABAC" 5 $flags
-distance "ACEBDABBABED" "ACBDEACBED" 6 $flags
+distance "1" "1" 0 "$flags"
+distance "1" "A" 2 "$flags"
+distance "123" "ABCDE" 8 "$flags"
+distance "ABCDE" "123" 8 "$flags"
+distance "ABD" "ABCD" 1 "$flags"
+distance "ABCD" "ABD" 1 "$flags"
+distance "ABCD" "ACDBECFD" 4 "$flags"
+distance "ABCDEF" "ABXYEFCD" 6 "$flags"
+distance "ABCDEFGHIJK" "ABCEFGIJKDEFGHIJK" 6 "$flags"
+distance "ABCABBA" "CBABAC" 5 "$flags"
+distance "ACEBDABBABED" "ACBDEACBED" 6 "$flags"
 
 touch EMPTY.tmp
 dif 1.tmp 1.tmp 0