much like the whitelist script as requested in #139

advanced/Scripts/blacklist.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# (c) 2015 by Jacob Salmela
+# This file is part of Pi-hole.
+#
+# Pi-hole is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+
+blackList=/etc/pihole/blacklist.txt
+if [[ ! -f $blackList ]];then
+    touch $blackList
+fi
+
+if [[ $# = 0 ]]; then
+    echo "Immediately blacklists one or more domains."
+    echo "Usage: blacklist.sh domain1 [domain2 ...]"
+fi
+
+boolA=false
+boolB=false
+for var in "$@"
+do
+		bool=false;
+    echo "Blacklisting $var..."
+    #add to whitelist.txt if it is not already there
+    grep -Ex -q "$var" $blackList || boolB=true
+    if $boolB; then
+        echo $var >> $blackList        
+        boolA=true;
+    else
+        echo "$var Already in blacklist.txt"
+    fi
+done
+
+if $boolA; then
+    echo "New domains added to blacklist. Running gravity.sh"
+    /usr/local/bin/gravity.sh
+else
+	echo "No need to update Hosts list, given domains already in blacklist"
+fi