diff --git a/Labb6/ovning4/add.sh b/Labb6/ovning4/add.sh
new file mode 120000
index 0000000..4e9c612
--- /dev/null
+++ b/Labb6/ovning4/add.sh
@@ -0,0 +1 @@
+calc.sh
\ No newline at end of file
diff --git a/Labb6/ovning4/calc.sh b/Labb6/ovning4/calc.sh
old mode 100644
new mode 100755
index 44a4203..17c9dac
--- a/Labb6/ovning4/calc.sh
+++ b/Labb6/ovning4/calc.sh
@@ -9,26 +9,68 @@
 Nr1=$1
 Nr2=$2
 
+# Sanity check
+if [ $# -ne 2 ]; then
+	echo "`basename $0` requires two arguments"
+	exit 2
+fi
+
+if ! [ $Nr1 -eq $Nr2 &> /dev/null ]; then
+	echo "`basename $0` only takes integers"
+	exit 2
+fi
+
 # Define our functions
 add()
 {
 	Sum=$((Nr1+Nr2))
+	return $Sum
 }
 
 sub()
 {
 	Sum=$((Nr1-Nr2))
+	return $Sum
 }
 
 div()
 {
 	Sum=$((Nr1/Nr2))
+	return $Sum
 }
 
 tim()
 {
-	Sum=$((Nr*Nr2))
+	Sum=$((Nr1*Nr2))
+	return $Sum
 }
 
 
 # Main
+Calc=`basename $0`
+echo $Calc
+
+case "$Calc" in
+	"add.sh")
+		add
+		echo $?
+		;;
+	"sub.sh")
+		sub
+		echo $?
+		;;
+	"div.sh")
+		div
+		echo $?
+		;;
+	"tim.sh")
+		tim
+		echo $?
+		;;
+	*)
+		echo "Please use on the symlink add.sh/sub.sh/div.sh/tim.sh"
+		exit 2
+		;;
+esac
+
+exit 0
diff --git a/Labb6/ovning4/div.sh b/Labb6/ovning4/div.sh
new file mode 120000
index 0000000..4e9c612
--- /dev/null
+++ b/Labb6/ovning4/div.sh
@@ -0,0 +1 @@
+calc.sh
\ No newline at end of file
diff --git a/Labb6/ovning4/sub.sh b/Labb6/ovning4/sub.sh
new file mode 120000
index 0000000..4e9c612
--- /dev/null
+++ b/Labb6/ovning4/sub.sh
@@ -0,0 +1 @@
+calc.sh
\ No newline at end of file
diff --git a/Labb6/ovning4/tim.sh b/Labb6/ovning4/tim.sh
new file mode 120000
index 0000000..4e9c612
--- /dev/null
+++ b/Labb6/ovning4/tim.sh
@@ -0,0 +1 @@
+calc.sh
\ No newline at end of file