diff --git a/tools/append_or_replace b/tools/append_or_replace
new file mode 100755
index 0000000..077c859
--- /dev/null
+++ b/tools/append_or_replace
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+
+usage() {
+	echo "Usage: $(basename "$0") <REGEX> <STRING> <FILE>"
+}
+
+if [[ $# -ne 3 ]]; then
+	usage
+	exit 2
+fi 
+
+REGEX=$1
+STRING=$2
+FILE=$3
+
+grep -q "$REGEX" $FILE
+if [ $? -eq 1 ]; then
+    echo "$STRING" >> $FILE
+	echo appended
+else
+    sed -i "s/$REGEX/$STRING/g" $FILE
+	echo replaced
+fi